Electrophysiologic Evaluation of Elderly Patients with Sinus Bradycardia A Long-Term Follow-Up Study DIETMAR GANN, M.D.; ALFONSO TOLENTINO, M.D.; and PHILIP SAMET, M.D.; Miami Beach and Coral Gables, Florida One hundred three patients with persistent sinus bradycardia were evaluated electrophysiologically and followed prospectively for a mean of 4.6 years. The 5-year survival rate was 7 4 . 8 % , not significantly different from the 7 2 % rate in the general population with similar age and sex distribution. Forty-one patients had abnormal corrected sinus-node recovery time. Overall accuracy of abnormal corrected sinus-node recovery time in predicting serious sinus node disease in symptomatic and asymptomatic patients was 9 0 % ( 3 7 of 4 1 patients) and 1 0 0 % in patients with syncope ( 1 8 of 18 patients). The sensitivity of the test was 6 6 % . Abnormal corrected sinus-node recovery time in patients with sinus bradycardia appears to be a valuable specific, predictive index of serious sinus node disease and therefore a useful test in selecting patients for pacemaker therapy, especially if symptoms such as dizziness or syncope are present. T H E SICK S I N U S S Y N D R O M E has received
considerable
a t t e n t i o n d u r i n g t h e last 10 y e a r s (1-4). D i z z i n e s s , syncope, a n d weakness are t h e major s y m p t o m s associated w i t h a d i s e a s e d s i n u s n o d e ( 3 , 4 ) . C o n g e s t i v e h e a r t failure is less c o m m o n . P e r m a n e n t p a c i n g often c o n t r o l s s y m p t o m s (5-8). S i n u s n o d e d i s o r d e r s a r e e s t i m a t e d t o a c c o u n t for 5 0 % of p e r m a n e n t p a c e m a k e r s i m p l a n t e d ( 2 ) . P e r s i s t e n t s i n u s b r a d y c a r d i a is t h e m o s t c o m m o n p r e s e n t a t i o n of a sick s i n u s s y n d r o m e , o c c u r r i n g f r e q u e n t l y in e l d e r l y p a t i e n t s , u s u a l l y in t h e r a n g e of 4 0 t o 55 b e a t s / m i n (9). E l d e r l y p a t i e n t s also c o m p l a i n f r e q u e n t l y of d i z z i n e s s a n d , less often, s y n c o p e . T h e r e f o r e , t h e p r a c t i c i n g p h y s i c i a n is often c o n f r o n t e d w i t h p a t i e n t s w i t h d i z z i n e s s o r s y n c o p e w h o also h a p p e n t o h a v e s i n u s b r a d y c a r d i a . E s tablishing a causal relation between s y m p t o m s a n d the b r a d y c a r d i a m a y b e difficult, e x p e n s i v e , a n d t i m e - c o n s u m i n g . W h a t is t h e n a t u r a l c o u r s e of p a t i e n t s w i t h a s y m p t o m a t i c b r a d y c a r d i a o r k n o w n sick s i n u s s y n d r o m e ? W h a t is t h e v a l u e of e l e c t r o p h y s i o l o g i c t e s t i n g ? E s p e c i a l l y , w h a t is t h e r o l e of s i n u s - n o d e r e c o v e r y t i m e in evaluating symptomatic patients with sinus bradycardia? F o r w h i c h p a t i e n t shall w e r e c o m m e n d p e r m a n e n t p a c ing? I n a n a t t e m p t t o solve s o m e of t h e s e m a n a g e m e n t p r o b l e m s , w e followed 103 e l d e r l y p a t i e n t s w i t h s i n u s b r a d y c a r d i a p r o s p e c t i v e l y for a m e a n p e r i o d of 4 . 6 y e a r s . All patients were evaluated electrophysiologically at t h e b e g i n n i n g of t h e s t u d y . W e p r e s e n t initial findings a n d follow-up data here. Materials and Methods A total of 117 patients with sinus bradycardia were referred to our cardiology service for electrophysiologic studies from • F r o m the Division of Cardiology, M o u n t Sinai Medical Center, Miami Beach; and the D e p a r t m e n t of Medicine, University of Miami School of Medicine; Coral Gables, Florida.
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Annals of Internal Medicine 9 0 : 2 4 - 2 9 , 1 9 7 9
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1969 to 1973. Fourteen of the original 117 were lost to followup; the study group therefore consisted of 103 patients. Sinus bradycardia was defined as a sinus rate persistently 55 beats/ min or less at rest, usually documented on two or more electrocardiograms over a period of several days or seen on continuous electrocardiographic monitoring. Patients with acute myocardial infarction or other medical illnesses that could be responsible for the bradycardia were not included; neither were those patients with drug-related bradycardia. Most of the patients presented with symptoms such as dizziness or syncope, or both. Electrophysiologic evaluation was done as previously described (10). Special emphasis was given to the corrected sinus-node recovery time. Sinus-node recovery time is the interval from the last paced beat to the first spontaneous sinus beat after 1 or 2 minutes of atrial pacing at various intervals from 120 to 140 per minute. The corrected sinus-node recovery time is derived by deducting the prepacing sinus cycle length from the sinus-node recovery time. The upper limit of normal in our laboratory for the corrected sinus-node recovery time is 525 msec. When we started our study in 1969, other potentially valuable tests for evaluating sinus node function were not yet available. Informed written consent was obtained for all studies. Follow-up data were available from our own records and from referring physicians. All patients were followed for a minimum of 3 years, or until death. Yearly mortality rates were calculated for a period of 5 years (according to the actuarial method [11]) and compared with derived mortality rates of the general population with a comparative age and sex distribution, as published by the United States Bureau of the Census (12). The patients were divided into three groups: Group I, 35 patients without symptoms and sinus bradycardia; Group II, 32 patients with dizziness and sinus bradycardia; and Group III, 36 patients with syncope and sinus bradycardia. Sensitivity and specificity of the corrected sinus-node recovery time in detecting abnormal sinus node function were defined in this manner: True positives X 100. Sensitivity % = True positives + false negatives Sensitivity describes the percentage of patients with sinus node disease requiring and benefiting from pacing who have abnormal corrected sinus-node recovery times. True negatives X 100 Specificity % = True negatives + false positives Specificity gives the percentage of negative results in subjects without the disease. True positives X 100 Predictive accuracy % = True positives + false positives Predictive accuracy describes the percentage of positive results that are truly positive. True-positives were patients with abnormal corrected sinusnode recovery time plus [a] additional findings of sinus node dysfunction other than sinus bradycardia, such as periods of sinus arrest and sinoatrial block; [b] persistent sinus bradycardia below 40 beats/min; or [c] symptomatic patients who received permanent pacemakers that controlled symptoms on follow-up and in whom no other cause of symptoms after thorough medical evaluation was found. True-negatives were patients with normal corrected sinusnode recovery time plus [a] no additional findings of sinus dys© 1 9 7 9 American College of Physicians
function on follow-up; or [b] symptomatic patients who only had sinus bradycardia and received permanent pacemakers but continued to have syncope or dizziness without documentable rhythm problems at the time of symptoms. False-positives were patients with abnormal corrected sinusnode recovery time who were asymptomatic and had no other evidence of abnormal sinus node function, including during the follow-up period. False-negatives were patients with normal corrected sinusnode recovery time and findings of sinus node dysfunction other than sinus bradycardia on initial evaluation or follow-up. This method of classification of patients into true- and falsenegative and true- and false-positive on the basis of ventricular rate, periods of sinoatrial block, sinus arrest, and symptoms is an arbitrary one. The sick sinus syndrome encompasses a spectrum of disease that electrocardiographically ranges from mild sinus bradycardia to long periods of sinus arrest. For example, we considered a rate of less than 40/min in an asymptomatic patient with an abnormal corrected sinus-node recovery time evidence of true sinus node disease; a similar patient with a slightly faster heart rate would have been classified as false-positive. Our definition of true-positive is fairly rigid and probably assures that only patients with significant sinus node dysfunction were included, but some patients considered true-negatives or false-positives may actually have had diseased sinus nodes. Results
A total of 103 patients with persisting sinus bradycardia were evaluated and followed for a mean of 4.6 years. All surviving patients were followed for a minimum of 3 years (range, 3 to 9 years). The mean age of all 103 patients was 72.2 years (range, 52 to 87 years). Sixty-seven patients were men and 36 women. Arteriosclerotic heart disease as documented by typical angina pectoris or a history of myocardial infarction was present in 70 patients (68%). However, arteriosclerotic heart disease was not the major clinical problem. Fifty-six of the 70 patients with arteriosclerotic heart disease were functional class 1 or 2. In 25 patients (24%), no cardiac disease was found other than the sinus bradycardia, and eight patients either had rheumatic heart disease, congenital heart disease, or hypertensive cardiovascular disease. Sixty-eight patients presented with either syncope or dizziness; 35 patients were asymptomatic. Forty-eight patients received permanent pacemakers during the initial evaluation. An additional eight needed pacemakers on follow-up. Forty-seven patients were not paced. Table 1. Abnormalities of Impulse Formation and Conduction in 103 Patients with Sinus Bradycardia Patients no. Abnormal corrected sinus node recovery time > 525 msec Electrocardiogram abnormalities Left axis deviation Right bundle branch block Right bundle branch block + left axis deviation Right bundle branch block + right axis deviation Left bundle branch block Intraventricular conduction defect Prolonged AH* time > 120 msec Prolonged HV f time > 45 msec Prolonged HV time > 55 msec
41 16 5 4 1 3 3 19 28 13
* AH = atrium to His. t HV = His to ventricle.
Table 2. Causes of Death in 30 Patients Who Died During Follow-up Patients Acute myocardial infarction Arteriosclerotic heart disease (died in nursing homes) Congestive heart failure Carcinoma Cerebrovascular accident Sudden death Mesenteric thrombosis Sepsis Respiratory failure Suicide
Of the 103 patients, 41 showed abnormal corrected sinus-node recovery time (Table 1). Fifty-seven patients (55%) showed a total of 79 additional conduction abnormalities. On the surface electrocardiogram 32 patients demonstrated left-axis deviation, right bundle branch block, left bundle branch block, or intraventricular conduction defects. Nineteen patients had prolonged atriumto-His time (longer than 120 msec). Twenty-eight patients had His-to-ventricle intervals longer than 45 msec; 13 of these were clearly prolonged (longer than 55 msec). If a patient presented with a ventricular rate below 4 0 / min, the likelihood of the corrected sinus-node recovery time being abnormal was 70% (seven of 10 patients). At ventricular rates of 40 to 45 per minute, an abnormal corrected sinus-node recovery time was present in 55% (20 of 36 patients). Patients with ventricular rates of 46 to 50 per minute and 50 to 55 per minute had almost equal percentages of abnormal corrected sinus-node recovery time; 25% at rates of 46 to 50 per minute (seven of 28 patients) and 24% at rates of 50 to 55 per minute (seven of 29 patients). Thirty patients died during the mean follow-up time of 4.6 years. The causes of death are listed in Table 2. One patient not paced died suddenly (cause of death undetermined) 2 years after the initial evaluation. This patient had had, in addition to sinus bradycardia, a right bundle branch block and left axis deviation, with a His-to-ventricle time of 55 msec. Four other patients died in nursing homes, two with and two without pacemakers. The cause of death in each case was listed as arteriosclerotic heart disease. More specific information as to the exact causes of death was unavailable. Calculated survival of our patients at the end of 5 years was 74.8%, with an SEM of ± 3.5. The survival of the general population in the United States with a similar mean age and sex distribution is 72%. This difference is not significant. The 5-year survival rate was 78% for 55 patients with sinus bradycardia who did not require a permanent pacemaker on initial evaluation. Sinus bradycardia alone in the elderly patient, if not associated with other severe heart disease, therefore has a good prognosis. In 64 patients an electrocardiogram documenting the heart rhythm was available at the end of the follow-up period. Thirty-three patients remained in sinus bradycardia (52%). In 15 patients the rhythm had changed to Gann eta/. • Sinus Bradycardia in Elderly Patients
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no. 8 4 4 6
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Table 3. Normal and Abnormal Corrected Sinus-Node Recovery Time (CSNRT) in Selecting Patients for Pacemaker Therapy
Paced Asymptomatic
Unpaced Asymptomatic
7*
17
Group I (35 patients) Normal CSNRT (24) Abnormal CSNRT (11) Group II (32 patients) Normal CSNRT (20) Abnormal CSNRT (12) Group III (36 patients) Normal CSNRT (18) Abnormal CSNRT (18)
7t
4t
6 9
8 1 (atrial fibrillation)
6 16
9
Paced Symptomatic
Unpaced Symptomatic
2 1
4 (noncardiac) 1 (refused pacer)
2 (dizziness)
1 (syncope) 2 (refused pacers)
* Permanent pacing for symptoms, sinus bradycardia at or below 40/m, and sinus arrest on follow-up. t Permanent pacing because of symptoms on follow-up. t One patient had 3- to 4-second asystole. Private physician decided not to pace.
atrial fibrillation (23%). Eleven patients at their last examinations had normal sinus rhythm with a ventricular rate above 60 beats/min (17%). Three patients were in complete heart block and two were in junctional rhythm. Of 35 patients with sinus bradycardia alone (without symptoms) during initial evaluation (Group I, Table 3), 11 showed abnormal corrected sinus-node recovery time and 24 normal corrected sinus-node recovery time. None of these patients received a pacemaker initially. Seven of the 11 with abnormal corrected sinus-node recovery time received permanent pacemakers for symptoms during the follow-up period that correlated with bradycardic rhythm or because of intermittent periods of prolonged asystole longer than 2 to 3 seconds. Of the 24 patients who had normal corrected sinus-node recovery time, only seven required permanent pacemakers over the next 4.6 years. The indications for pacing in these seven patients were the demonstration of asystolic periods longer than 2.5 seconds or intermittent prolonged slowing of the sinus rate below 40 beats/min. None was restudied, and therefore we do not know if the corrected sinus-node recovery time remained normal. Thirty-two patients presented with dizziness and sinus bradycardia (Group II, Table 3). Twelve showed abnormal corrected sinus-node recovery time. Ten of these 12 were paced, and, of these 10, nine became and remained asymptomatic. Of the two nonpaced patients with abnormal corrected sinus-node recovery time, one developed atrial fibrillation several days after study and became Table 4. Specificity, Sensitivity, and Predictive Accuracy of Corrected Sinus Node Recovery Time (CSNRT)* Specificity
Total patients (103) f Group I (35 patients, no symptoms) Group II (32 patients with dizziness) Group III (36 patients with syncope)
;Sensitivity
Predictive Accuracy
%
%
%~
91
66
90
85
53
73
93
65
92
100
75
100
* For definitions, see Materials and Methods. t Forty-one patients had abnormal CSNRT: 37 true-positive, four falsepositive; 62 patients had normal CSNRT: 43 true-negative , 19 falsenegative.
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1979
• Annals of Internal Medicine • Volume 90 • Number
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asymptomatic; another refused a pacemaker and continued to have dizzy spells. Twenty of the 32 patients had normal corrected sinus-node recovery time. Eight of those 20 were paced during follow-up, primarily because of prolonged periods of asystole longer than 2.5 seconds during repeated monitoring; of the eight paced patients, six became or were asymptomatic at the end of the follow-up period; again, none of those eight was restudied. We do not know if the corrected sinus-node recovery time was normal at the time a pacemaker was inserted. Of the 12 with normal corrected sinus-node recovery time who did not receive pacemakers, four have dizzy spells without demonstrable cause (cardiac or noncardiac) and eight are asymptomatic. Thirty-six patients suffered syncopal episodes (Group III, Table 3). Eighteen of them had abnormal corrected sinus-node recovery time. Of these 18, 16 were paced and all became asymptomatic. The two unpaced patients refused pacemakers and remained symptomatic. Of the remaining 18 with normal corrected sinus-node recovery time, eight needed permanent pacemakers because repeated continuous monitoring showed significant asystolic periods (longer than 2 seconds). Two of these eight patients continued to have dizzy spells after pacing. Of 10 nonpaced patients with normal corrected sinus-node recovery time, nine became and remained asymptomatic and one continued to have syncopal episodes of undetermined noncardiac origin. The mean corrected sinus-node recovery times between the three groups were compared with the unpaired t test. No significant difference was found. Of 41 patients with abnormal corrected sinus-node recovery time, 37 had definite sinus node disease (true-positives) and four had no serious sinus node problems (falsepositives). Of 62 patients with normal corrected sinusnode recovery time, 43 showed no evidence during follow-up time of serious sinus node problems (true-negatives) and 19 patients either required pacemakers or had long periods of sinoatrial block or sinus arrest (false-negatives). The specificity of an abnormal corrected sinusnode recovery time was 91 % and the predictive accuracy 90% for all 41 patients studied (Table 4). This means that an abnormal corrected sinus-node recovery time was predicted in 90% of patients with serious sinus node disease, with a potential indication for permanent pacing in 1
appropriate patients. If, in addition, symptoms are taken into consideration, the following predictive accuracy is obtained (see Table 4): asymptomatic patients with abnormal corrected sinus node recpvery time, 73%; patients with dizziness and abnormal corrected sinus-node recovery time, 92%; and patients with syncope and abnormal corrected sinus-node recovery time, 100%. Fifty-six patients had definite sinus node disease as documented by periods of sinus arrest or sinoatrial block during the follow-up period. The corrected sinus-node recovery time was abnormal in only 37 of the 56 patients (sensitivity, 66%). If we correlate the symptoms in these 56 patients, the sensitivity is 53% for asymptomatic patients, 65% for patients with dizziness, and 75% for patients with syncope. We have compared the corrected sinus-node recovery time obtained at the beginning of the study with the appearance of sinus node dysfunction at various intervals during the follow-up time. If repeat conduction studies had been done when sinus node dysfunction became evident, more abnormal sinus-node recovery times may have been found and the sensitivity of the corrected sinus-node recovery time may actually have been higher. The sensitivity of the corrected sinus-node recovery time may also have been improved if a wider range of pacing rates had been used; for example, 60 to 150 per minute rather than 120 to 140 per minute. This wider range of pacing is now used; its importance was not recognized when our study began. Sinus-node recovery time may also be reported as uncorrected sinus-node recovery time (interval from the last paced beat to the first spontaneous sinus beat) or in terms of uncorrected sinus-node recovery time divided by basic cycle length. The uncorrected sinus-node recovery time in our 41 patients with abnormal corrected sinus-node recovery time ranged from 1430 to 6240 msec. For the 62 patients with normal corrected sinus-node recovery time, the uncorrected sinus-node recovery time ranged from 940 to 1780 msec. Dividing uncorrected sinus-node recovery time by basic cycle length in the 41 patients with abnormal corrected sinus-node recovery time gave values of 1.38 to 4.86; in the 62 patients with normal corrected sinus-node recovery time, the calculated values ranged from 1.05 to 1.46. Only three of these latter 62 patients had values greater than 1.38. Therefore, the method of dividing uncorrected sinus-node recovery time by basic cycle length separated our patients into groups of normals and abnormals similar to those obtained by using the corrected sinus-node recovery time. Discussion
Two recent editorials on the sick sinus syndrome ( 1 , 2 ) stress our incomplete knowledge of the natural course of a patient with a diseased sinus node, specifically our inability to predict which patient will need a permanent pacemaker to prevent or treat symptoms that are related to a malfunctioning sinus node. A report from England (13) on 46 patients with sinus bradycardia concluded that most of these patients had a pathologic form of sinus bradycardia. Thirty-six of the 46 patients had syncopal
attacks or dizzy spells. Only one patient, however, required a permanent pacemaker to control frequent syncopal attacks. This report was published in 1971. In 1978, at least in the United States, most symptomatic patients would probably have received permanent pacemakers during the initial evaluation, other causes for symptoms having been excluded. In 1975, 13 times as many pacemakers per million people were inserted in the United States as in Great Britain. It may well be that not enough pacemakers are inserted in Great Britain, but quite possibly too many are inserted in this country. The sick sinus syndrome is becoming the single most common indication for permanent pacing, accounting for up to 50% of all inserted permanent pacemakers (2). Better definitions for permanent pacing in the sick sinus syndrome are needed. The mere presence of sick sinus syndrome as defined by the New York Heart Association Classification is not enough to make a decision for or against pacing. Our data suggest that sinus bradycardia as the sole manifestation of cardiac disease in the elderly patient has little effect on mortality. The overall 5-year survival of nonpaced patients with sinus bradycardia was even slightly higher than that in the general population (78% versus 72%). In viewing the good survival rate of the nonpaced patients, one must consider that most of these patients were either asymptomatic or had dizziness (without specific cause found). None of the patients had a severely compromised cardiac status, none was in functional Class 4, and only five were in functional Class 3 because of angina. Additionally, none of these patients had significant congestive heart failure. Only one of the 55 patients who had not received a pacemaker during the initial evaluation died suddenly as a consequence of possible rhythm disturbance. The patient was initially asymptomatic with a normal corrected sinus-node recovery time, had additional right bundle branch block and left axis deviation, and a prolonged His-to-ventricle time. Another eight of the 55 patients who were not paced initially developed syncope or dizziness, with slow heart rates during the follow-up period, and were treated with pacing. In each of these eight patients, the need for pacing was established by correlating symptoms with significant bradycardia on repeated monitoring. None of these patients suffered irreversible damage during the symptomatic episodes. Another four of the 55 patients had recurrent syncope (two patients) or recurrent dizziness (two patients) and refused permanent pacemakers. Continuous electrocardiographic monitoring clearly established that the bradycardic rhythm was responsible for symptoms. They have been followed now for 3, 3.5, 6, and 7 years, respectively, and are all still alive. The 5-year survival rate of 48 patients who were paced initially was 70%, not significantly different from that in the general population (72%). Our data do not permit us to state whether pacing symptomatic patients with sinus node problems prolongs life. The number of patients who had clearly abnormal and symptomatic sinus node disorders and who were not paced is too small to draw any conclusions from their outcome. A diseased sinus node Gann et al. • Sinus Bradycardia in Elderly Patients
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27
seems less likely to cause death, unlike complete heart block where 50% of unpaced patients are dead within 1 year (14). Our data suggest that there is no need for pacing in asymptomatic patients with sinus bradycardia, even if this appears to be a true manifestation of sick sinus syndrome. Patients with persistent heart rates below 40/min may be exceptions, but these patients rarely are asymptomatic. In the group of 11 asymptomatic patients with abnormal corrected sinus-node recovery time, eight eventually became candidates for permanent pacing because they became symptomatic or developed long periods of asystole. However, the interval from documentation of the abnormal sinus function to development of symptoms varied from a few months to as long as 6 years. None of the patients suffered irreversible damage or died as a consequence of the malfunctioning sinus node. Therefore we do not suggest routinely doing sinus-node recovery times in asymptomatic patients with sinus bradycardia. There is probably little disagreement that patients with abnormally functioning sinus nodes frequently have disease in the remainder of the conduction system. This has been confirmed in our study. Fifty-five percent of 103 patients had additional abnormalities of conduction in the atrioventricular node or interventricular conduction system. Therefore, if atrial pacing is considered for any patient, the rest of the conduction system should be initially evaluated and this mode of therapy used only if conduction through the atrioventricular node and interventricular conduction system is intact. Several reports have shown that the most useful test for detecting abnormal sinus node function is the sinusnode recovery time (10, 15-18). Two studies dealing with relatively small groups of patients did not find the sinusnode recovery time to be very helpful (19, 20). Additional tests such as measurement of sinoatrial conduction time, response to atropine, repetition of sinus-node recovery time after atropine, and evaluation of the first 10 beats after cessation of atrial pacing all have merit. We did not routinely use these additional tests when our study began and therefore will not comment further on their value. At present we may use any or all of these tests in selected patients. Persistent sinus bradycardia below 55 beats/min in the elderly patient frequently is an expression of malfunctioning sinus node. Is it therefore helpful to add a test that merely proves that the sinus node is truly diseased? Based on the findings in this study, we believe that an abnormal corrected sinus-node recovery time occurs only in patients with fairly advanced sinus node dysfunction. An abnormal corrected sinus-node recovery time did prove to be a very reliable confirmatory indication of which patient might need and benefit from permanent pacing. We believe that all patients with symptomatic sinus bradycardia and abnormal corrected sinus-node recovery time should be permanently paced. On the other hand, the finding of a normal corrected sinus-node recovery time does not exclude serious sinus node dysfunction. Measurement of a sinus-node recovery time has, in our opinion, been most helpful in symptomatic patients with 28
sinus bradycardia with heart rates above 40/min in whom no clear relation between symptoms and slow heart rate, even with continuous monitoring, could be established. This is a very common presentation. Assuming that no other medical reasons for symptoms could be found, an abnormal corrected sinus-node recovery time predicted that symptoms could be controlled with pacing in 100% of patients with syncope and 9 1 % of patients with dizziness. Measurement of corrected sinus-node recovery time in these patients may help shorten hospital stay substantially and make numerous costly 24-h electrocardiographic monitoring periods unnecessary. We should also consider the value of a sinus-node recovery time from a different point of view. One may suggest insertion of a permanent pacemaker in a patient with sinus bradycardia and symptoms if no other cause for the symptoms can be found. However, 40% of our patients with dizziness and 28% with syncope under the latter circumstances needed no pacemaker as determined by our follow-up time of 4.6 years. All of these were patients with normal corrected sinus-node recovery time. Therefore, the findings on a pacing study can be used to better separate those patients more likely to benefit symptomatically from pacing from those who would not. We confirm previous reports (5-8) that permanent pacing in properly selected patients frequently controls symptoms related to a diseased sinus node. Of 23 patients with syncope and permanent pacemaker insertion at the beginning of the study, only two continued to have symptoms, and of 17 patients with dizziness who were permanently paced, three remained symptomatic. Therefore, of 40 patients with sinus node dysfunction and symptoms who were permanently paced, only five continued to have some intermittent symptoms; 87.5% of patients became asymptomatic with pacing. From these findings, we suggest this approach for managing elderly patients with sinus bradycardia. 1. Asymptomatic sinus bradycardia—observe only. There is no need for prolonged monitoring. Persistent sinus bradycardia at rest below 40 beats/min may be an indication for permanent pacing in asymptomatic patients. However, patients are usually symptomatic at these slow rates. 2. Symptomatic sinus bradycardia—rule out other causes for symptoms and continue evaluation with 24-h electrocardiographic monitoring. A pacemaker is indicated if the patient becomes symptomatic during monitoring and has slow heart rates at the same time. Symptoms without severe bradycardia or periods of sinus arrest virtually exclude a diseased sinus node as the cause. Many of the patients who are monitored will not be symptomatic during the monitoring period. These patients should undergo electrophysiologic evaluation. An abnormal corrected sinus-node recovery time is clearly an indication for permanent pacing in the symptomatic patient. If a normal corrected sinus-node recovery time is present, we suggest further observation. Multiple 24-h recordings may be needed in these patients. Additional tests to measure sinus node function such as administration of atropine (21), measurement of sinus-node recovery time after
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atropine, conduction of the first 10 beats after cessation of pacing (22, 23), or measurement of intrinsic heart rates after administration of atropine and propanolol (24) may find other patients who need permanent pacing. • Requests for reprints should be addressed to Dietmar Gann, M.D.; Division of Cardiology, Mount Sinai Medical Center; Miami Beach, F L 33140. Received 8 May 1978; revision accepted 3 October 1978.
11. A N D E R S O N R P , B O N C H E K LI, G R U N K M E I E R GL,
L A M B E R T LE,
STARR A: The analysis and presentation of surgical results by actuarial methods. J Surg Res 16:224-230, 1974 12. Statistical Abstract of the United States, 1976, 97th ed. Washington, D.C., U.S. Bureau of the Census, 1976 13. ERAUS D, S H A W DB: Sinus bradycardia. Br Heart J 33:742-749, 1971 14. FRIEDBERG CK, DONOSO E, STEIN EG: Nonsurgical acquired heart block. Ann NY Acad Sci 111:835-847, 1964 15. STRAUSS HC, B I G G E R JT J R , SAROFF AL, G I A R D I N A EGV: Electro-
physiologic evaluation of sinus node function in patients with sinus node dysfunction. Circulation 53:763-776, 1976 16. T O Y A M A J, I T O A, S A W A D A K, T A N A H A S H I Y, T S U Z U K I J, W A T A N -
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sinoatrial rhythm disturbances with permanent cardiac pacing. Am J Cardiol 32:215-220, 1973 7. H A R T E L G, TALVENSAARI T: Treatment of sinoatrial syndrome with permanent cardiac pacing in 90 patients. Acta Med Scand 198:341-347, 1975 8. W O H L AJ, L A B O R D E NJ, A T K I N S JM, B L O M Q V I S T CG, M U L L I N S CB:
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node recovery time in the elderly. Br Heart J 37:420-425, 1975 10. N A R U L A OS, S A M E T P, J A V I E R R P : Significance of the sinus-node re-
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ABE T, YASUI S: Overdrive suppression in diagnosis of sick sinus syndrome. J Electrocardiol 8:209-216, 1975 17. EVANS TR, C A L L O W H I L L EA, K R I K L E R DM: Clinical value of tests of sinoatrial function. Pacing Clin Electrophysiol 1:2-7, 1978 18. M A N D E L WJ, OBAYASHI K, LAKS MM: Overview of the sick sinus syndrome (editorial). Chest 66:223, 1974 19. C R O O K B, K I T S O N D, M C C O M I S H M, J E W I T T D: What is role of clini-
cal electrophysiology in evaluation of patients with sinoatrial disease? Br Heart 7 38:879-880, 1976 20. G U P T A PK, LICHSTEIN E, C H A D D A K D , B A D U I E: Appraisal of sinus
nodal recovery time in patients with sick sinus syndrome. Am J Cardiol 34:265-270, 1974 21. D H I N G R A RC, A M A T - Y - L E O N F, W Y N D H A M C, D E N E S P, W U D,
M I L L E R RH, ROSEN KM: Electrophysiologic effects of atropine on sinus node and atrium in patients with sinus nodal dysfunction. Am J Cardiol 38:848-855, 1976 22. C H A D D A K D , B A N K A VS, B O D E N H E I M E R M M , H E L F A N T R H : Cor-
rected sinus node recovery time. Experimental physiologic and pathologic determinants. Circulation 51:797-801, 1975 23. B E N D I T T D G , STRAUSS HC, S C H E I N M A N M M , B E H A R VS, W A L L A C E
AG: Analysis of secondary pauses following termination of rapid atrial pacing in man. Circulation 54:436-441, 1976 24. J O R D A N JL, Y A M A G U C H I I, M A N D E L WJ: Studies on the mechanism of
sinus node dysfunction in the sick sinus syndrome. Circulation 57:217223, 1978
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considerable
a t t e n t i o n d u r i n g t h e last 10 y e a r s (1-4). D i z z i n e s s , syncope, a n d weakness are t h e major s y m p t o m s associated w i t h a d i s e a s e d s i n u s n o d e ( 3 , 4 ) . C o n g e s t i v e h e a r t failure is less c o m m o n . P e r m a n e n t p a c i n g often c o n t r o l s s y m p t o m s (5-8). S i n u s n o d e d i s o r d e r s a r e e s t i m a t e d t o a c c o u n t for 5 0 % of p e r m a n e n t p a c e m a k e r s i m p l a n t e d ( 2 ) . P e r s i s t e n t s i n u s b r a d y c a r d i a is t h e m o s t c o m m o n p r e s e n t a t i o n of a sick s i n u s s y n d r o m e , o c c u r r i n g f r e q u e n t l y in e l d e r l y p a t i e n t s , u s u a l l y in t h e r a n g e of 4 0 t o 55 b e a t s / m i n (9). E l d e r l y p a t i e n t s also c o m p l a i n f r e q u e n t l y of d i z z i n e s s a n d , less often, s y n c o p e . T h e r e f o r e , t h e p r a c t i c i n g p h y s i c i a n is often c o n f r o n t e d w i t h p a t i e n t s w i t h d i z z i n e s s o r s y n c o p e w h o also h a p p e n t o h a v e s i n u s b r a d y c a r d i a . E s tablishing a causal relation between s y m p t o m s a n d the b r a d y c a r d i a m a y b e difficult, e x p e n s i v e , a n d t i m e - c o n s u m i n g . W h a t is t h e n a t u r a l c o u r s e of p a t i e n t s w i t h a s y m p t o m a t i c b r a d y c a r d i a o r k n o w n sick s i n u s s y n d r o m e ? W h a t is t h e v a l u e of e l e c t r o p h y s i o l o g i c t e s t i n g ? E s p e c i a l l y , w h a t is t h e r o l e of s i n u s - n o d e r e c o v e r y t i m e in evaluating symptomatic patients with sinus bradycardia? F o r w h i c h p a t i e n t shall w e r e c o m m e n d p e r m a n e n t p a c ing? I n a n a t t e m p t t o solve s o m e of t h e s e m a n a g e m e n t p r o b l e m s , w e followed 103 e l d e r l y p a t i e n t s w i t h s i n u s b r a d y c a r d i a p r o s p e c t i v e l y for a m e a n p e r i o d of 4 . 6 y e a r s . All patients were evaluated electrophysiologically at t h e b e g i n n i n g of t h e s t u d y . W e p r e s e n t initial findings a n d follow-up data here. Materials and Methods A total of 117 patients with sinus bradycardia were referred to our cardiology service for electrophysiologic studies from • F r o m the Division of Cardiology, M o u n t Sinai Medical Center, Miami Beach; and the D e p a r t m e n t of Medicine, University of Miami School of Medicine; Coral Gables, Florida.
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Annals of Internal Medicine 9 0 : 2 4 - 2 9 , 1 9 7 9
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1969 to 1973. Fourteen of the original 117 were lost to followup; the study group therefore consisted of 103 patients. Sinus bradycardia was defined as a sinus rate persistently 55 beats/ min or less at rest, usually documented on two or more electrocardiograms over a period of several days or seen on continuous electrocardiographic monitoring. Patients with acute myocardial infarction or other medical illnesses that could be responsible for the bradycardia were not included; neither were those patients with drug-related bradycardia. Most of the patients presented with symptoms such as dizziness or syncope, or both. Electrophysiologic evaluation was done as previously described (10). Special emphasis was given to the corrected sinus-node recovery time. Sinus-node recovery time is the interval from the last paced beat to the first spontaneous sinus beat after 1 or 2 minutes of atrial pacing at various intervals from 120 to 140 per minute. The corrected sinus-node recovery time is derived by deducting the prepacing sinus cycle length from the sinus-node recovery time. The upper limit of normal in our laboratory for the corrected sinus-node recovery time is 525 msec. When we started our study in 1969, other potentially valuable tests for evaluating sinus node function were not yet available. Informed written consent was obtained for all studies. Follow-up data were available from our own records and from referring physicians. All patients were followed for a minimum of 3 years, or until death. Yearly mortality rates were calculated for a period of 5 years (according to the actuarial method [11]) and compared with derived mortality rates of the general population with a comparative age and sex distribution, as published by the United States Bureau of the Census (12). The patients were divided into three groups: Group I, 35 patients without symptoms and sinus bradycardia; Group II, 32 patients with dizziness and sinus bradycardia; and Group III, 36 patients with syncope and sinus bradycardia. Sensitivity and specificity of the corrected sinus-node recovery time in detecting abnormal sinus node function were defined in this manner: True positives X 100. Sensitivity % = True positives + false negatives Sensitivity describes the percentage of patients with sinus node disease requiring and benefiting from pacing who have abnormal corrected sinus-node recovery times. True negatives X 100 Specificity % = True negatives + false positives Specificity gives the percentage of negative results in subjects without the disease. True positives X 100 Predictive accuracy % = True positives + false positives Predictive accuracy describes the percentage of positive results that are truly positive. True-positives were patients with abnormal corrected sinusnode recovery time plus [a] additional findings of sinus node dysfunction other than sinus bradycardia, such as periods of sinus arrest and sinoatrial block; [b] persistent sinus bradycardia below 40 beats/min; or [c] symptomatic patients who received permanent pacemakers that controlled symptoms on follow-up and in whom no other cause of symptoms after thorough medical evaluation was found. True-negatives were patients with normal corrected sinusnode recovery time plus [a] no additional findings of sinus dys© 1 9 7 9 American College of Physicians
function on follow-up; or [b] symptomatic patients who only had sinus bradycardia and received permanent pacemakers but continued to have syncope or dizziness without documentable rhythm problems at the time of symptoms. False-positives were patients with abnormal corrected sinusnode recovery time who were asymptomatic and had no other evidence of abnormal sinus node function, including during the follow-up period. False-negatives were patients with normal corrected sinusnode recovery time and findings of sinus node dysfunction other than sinus bradycardia on initial evaluation or follow-up. This method of classification of patients into true- and falsenegative and true- and false-positive on the basis of ventricular rate, periods of sinoatrial block, sinus arrest, and symptoms is an arbitrary one. The sick sinus syndrome encompasses a spectrum of disease that electrocardiographically ranges from mild sinus bradycardia to long periods of sinus arrest. For example, we considered a rate of less than 40/min in an asymptomatic patient with an abnormal corrected sinus-node recovery time evidence of true sinus node disease; a similar patient with a slightly faster heart rate would have been classified as false-positive. Our definition of true-positive is fairly rigid and probably assures that only patients with significant sinus node dysfunction were included, but some patients considered true-negatives or false-positives may actually have had diseased sinus nodes. Results
A total of 103 patients with persisting sinus bradycardia were evaluated and followed for a mean of 4.6 years. All surviving patients were followed for a minimum of 3 years (range, 3 to 9 years). The mean age of all 103 patients was 72.2 years (range, 52 to 87 years). Sixty-seven patients were men and 36 women. Arteriosclerotic heart disease as documented by typical angina pectoris or a history of myocardial infarction was present in 70 patients (68%). However, arteriosclerotic heart disease was not the major clinical problem. Fifty-six of the 70 patients with arteriosclerotic heart disease were functional class 1 or 2. In 25 patients (24%), no cardiac disease was found other than the sinus bradycardia, and eight patients either had rheumatic heart disease, congenital heart disease, or hypertensive cardiovascular disease. Sixty-eight patients presented with either syncope or dizziness; 35 patients were asymptomatic. Forty-eight patients received permanent pacemakers during the initial evaluation. An additional eight needed pacemakers on follow-up. Forty-seven patients were not paced. Table 1. Abnormalities of Impulse Formation and Conduction in 103 Patients with Sinus Bradycardia Patients no. Abnormal corrected sinus node recovery time > 525 msec Electrocardiogram abnormalities Left axis deviation Right bundle branch block Right bundle branch block + left axis deviation Right bundle branch block + right axis deviation Left bundle branch block Intraventricular conduction defect Prolonged AH* time > 120 msec Prolonged HV f time > 45 msec Prolonged HV time > 55 msec
41 16 5 4 1 3 3 19 28 13
* AH = atrium to His. t HV = His to ventricle.
Table 2. Causes of Death in 30 Patients Who Died During Follow-up Patients Acute myocardial infarction Arteriosclerotic heart disease (died in nursing homes) Congestive heart failure Carcinoma Cerebrovascular accident Sudden death Mesenteric thrombosis Sepsis Respiratory failure Suicide
Of the 103 patients, 41 showed abnormal corrected sinus-node recovery time (Table 1). Fifty-seven patients (55%) showed a total of 79 additional conduction abnormalities. On the surface electrocardiogram 32 patients demonstrated left-axis deviation, right bundle branch block, left bundle branch block, or intraventricular conduction defects. Nineteen patients had prolonged atriumto-His time (longer than 120 msec). Twenty-eight patients had His-to-ventricle intervals longer than 45 msec; 13 of these were clearly prolonged (longer than 55 msec). If a patient presented with a ventricular rate below 4 0 / min, the likelihood of the corrected sinus-node recovery time being abnormal was 70% (seven of 10 patients). At ventricular rates of 40 to 45 per minute, an abnormal corrected sinus-node recovery time was present in 55% (20 of 36 patients). Patients with ventricular rates of 46 to 50 per minute and 50 to 55 per minute had almost equal percentages of abnormal corrected sinus-node recovery time; 25% at rates of 46 to 50 per minute (seven of 28 patients) and 24% at rates of 50 to 55 per minute (seven of 29 patients). Thirty patients died during the mean follow-up time of 4.6 years. The causes of death are listed in Table 2. One patient not paced died suddenly (cause of death undetermined) 2 years after the initial evaluation. This patient had had, in addition to sinus bradycardia, a right bundle branch block and left axis deviation, with a His-to-ventricle time of 55 msec. Four other patients died in nursing homes, two with and two without pacemakers. The cause of death in each case was listed as arteriosclerotic heart disease. More specific information as to the exact causes of death was unavailable. Calculated survival of our patients at the end of 5 years was 74.8%, with an SEM of ± 3.5. The survival of the general population in the United States with a similar mean age and sex distribution is 72%. This difference is not significant. The 5-year survival rate was 78% for 55 patients with sinus bradycardia who did not require a permanent pacemaker on initial evaluation. Sinus bradycardia alone in the elderly patient, if not associated with other severe heart disease, therefore has a good prognosis. In 64 patients an electrocardiogram documenting the heart rhythm was available at the end of the follow-up period. Thirty-three patients remained in sinus bradycardia (52%). In 15 patients the rhythm had changed to Gann eta/. • Sinus Bradycardia in Elderly Patients
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no. 8 4 4 6
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Table 3. Normal and Abnormal Corrected Sinus-Node Recovery Time (CSNRT) in Selecting Patients for Pacemaker Therapy
Paced Asymptomatic
Unpaced Asymptomatic
7*
17
Group I (35 patients) Normal CSNRT (24) Abnormal CSNRT (11) Group II (32 patients) Normal CSNRT (20) Abnormal CSNRT (12) Group III (36 patients) Normal CSNRT (18) Abnormal CSNRT (18)
7t
4t
6 9
8 1 (atrial fibrillation)
6 16
9
Paced Symptomatic
Unpaced Symptomatic
2 1
4 (noncardiac) 1 (refused pacer)
2 (dizziness)
1 (syncope) 2 (refused pacers)
* Permanent pacing for symptoms, sinus bradycardia at or below 40/m, and sinus arrest on follow-up. t Permanent pacing because of symptoms on follow-up. t One patient had 3- to 4-second asystole. Private physician decided not to pace.
atrial fibrillation (23%). Eleven patients at their last examinations had normal sinus rhythm with a ventricular rate above 60 beats/min (17%). Three patients were in complete heart block and two were in junctional rhythm. Of 35 patients with sinus bradycardia alone (without symptoms) during initial evaluation (Group I, Table 3), 11 showed abnormal corrected sinus-node recovery time and 24 normal corrected sinus-node recovery time. None of these patients received a pacemaker initially. Seven of the 11 with abnormal corrected sinus-node recovery time received permanent pacemakers for symptoms during the follow-up period that correlated with bradycardic rhythm or because of intermittent periods of prolonged asystole longer than 2 to 3 seconds. Of the 24 patients who had normal corrected sinus-node recovery time, only seven required permanent pacemakers over the next 4.6 years. The indications for pacing in these seven patients were the demonstration of asystolic periods longer than 2.5 seconds or intermittent prolonged slowing of the sinus rate below 40 beats/min. None was restudied, and therefore we do not know if the corrected sinus-node recovery time remained normal. Thirty-two patients presented with dizziness and sinus bradycardia (Group II, Table 3). Twelve showed abnormal corrected sinus-node recovery time. Ten of these 12 were paced, and, of these 10, nine became and remained asymptomatic. Of the two nonpaced patients with abnormal corrected sinus-node recovery time, one developed atrial fibrillation several days after study and became Table 4. Specificity, Sensitivity, and Predictive Accuracy of Corrected Sinus Node Recovery Time (CSNRT)* Specificity
Total patients (103) f Group I (35 patients, no symptoms) Group II (32 patients with dizziness) Group III (36 patients with syncope)
;Sensitivity
Predictive Accuracy
%
%
%~
91
66
90
85
53
73
93
65
92
100
75
100
* For definitions, see Materials and Methods. t Forty-one patients had abnormal CSNRT: 37 true-positive, four falsepositive; 62 patients had normal CSNRT: 43 true-negative , 19 falsenegative.
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1979
• Annals of Internal Medicine • Volume 90 • Number
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asymptomatic; another refused a pacemaker and continued to have dizzy spells. Twenty of the 32 patients had normal corrected sinus-node recovery time. Eight of those 20 were paced during follow-up, primarily because of prolonged periods of asystole longer than 2.5 seconds during repeated monitoring; of the eight paced patients, six became or were asymptomatic at the end of the follow-up period; again, none of those eight was restudied. We do not know if the corrected sinus-node recovery time was normal at the time a pacemaker was inserted. Of the 12 with normal corrected sinus-node recovery time who did not receive pacemakers, four have dizzy spells without demonstrable cause (cardiac or noncardiac) and eight are asymptomatic. Thirty-six patients suffered syncopal episodes (Group III, Table 3). Eighteen of them had abnormal corrected sinus-node recovery time. Of these 18, 16 were paced and all became asymptomatic. The two unpaced patients refused pacemakers and remained symptomatic. Of the remaining 18 with normal corrected sinus-node recovery time, eight needed permanent pacemakers because repeated continuous monitoring showed significant asystolic periods (longer than 2 seconds). Two of these eight patients continued to have dizzy spells after pacing. Of 10 nonpaced patients with normal corrected sinus-node recovery time, nine became and remained asymptomatic and one continued to have syncopal episodes of undetermined noncardiac origin. The mean corrected sinus-node recovery times between the three groups were compared with the unpaired t test. No significant difference was found. Of 41 patients with abnormal corrected sinus-node recovery time, 37 had definite sinus node disease (true-positives) and four had no serious sinus node problems (falsepositives). Of 62 patients with normal corrected sinusnode recovery time, 43 showed no evidence during follow-up time of serious sinus node problems (true-negatives) and 19 patients either required pacemakers or had long periods of sinoatrial block or sinus arrest (false-negatives). The specificity of an abnormal corrected sinusnode recovery time was 91 % and the predictive accuracy 90% for all 41 patients studied (Table 4). This means that an abnormal corrected sinus-node recovery time was predicted in 90% of patients with serious sinus node disease, with a potential indication for permanent pacing in 1
appropriate patients. If, in addition, symptoms are taken into consideration, the following predictive accuracy is obtained (see Table 4): asymptomatic patients with abnormal corrected sinus node recpvery time, 73%; patients with dizziness and abnormal corrected sinus-node recovery time, 92%; and patients with syncope and abnormal corrected sinus-node recovery time, 100%. Fifty-six patients had definite sinus node disease as documented by periods of sinus arrest or sinoatrial block during the follow-up period. The corrected sinus-node recovery time was abnormal in only 37 of the 56 patients (sensitivity, 66%). If we correlate the symptoms in these 56 patients, the sensitivity is 53% for asymptomatic patients, 65% for patients with dizziness, and 75% for patients with syncope. We have compared the corrected sinus-node recovery time obtained at the beginning of the study with the appearance of sinus node dysfunction at various intervals during the follow-up time. If repeat conduction studies had been done when sinus node dysfunction became evident, more abnormal sinus-node recovery times may have been found and the sensitivity of the corrected sinus-node recovery time may actually have been higher. The sensitivity of the corrected sinus-node recovery time may also have been improved if a wider range of pacing rates had been used; for example, 60 to 150 per minute rather than 120 to 140 per minute. This wider range of pacing is now used; its importance was not recognized when our study began. Sinus-node recovery time may also be reported as uncorrected sinus-node recovery time (interval from the last paced beat to the first spontaneous sinus beat) or in terms of uncorrected sinus-node recovery time divided by basic cycle length. The uncorrected sinus-node recovery time in our 41 patients with abnormal corrected sinus-node recovery time ranged from 1430 to 6240 msec. For the 62 patients with normal corrected sinus-node recovery time, the uncorrected sinus-node recovery time ranged from 940 to 1780 msec. Dividing uncorrected sinus-node recovery time by basic cycle length in the 41 patients with abnormal corrected sinus-node recovery time gave values of 1.38 to 4.86; in the 62 patients with normal corrected sinus-node recovery time, the calculated values ranged from 1.05 to 1.46. Only three of these latter 62 patients had values greater than 1.38. Therefore, the method of dividing uncorrected sinus-node recovery time by basic cycle length separated our patients into groups of normals and abnormals similar to those obtained by using the corrected sinus-node recovery time. Discussion
Two recent editorials on the sick sinus syndrome ( 1 , 2 ) stress our incomplete knowledge of the natural course of a patient with a diseased sinus node, specifically our inability to predict which patient will need a permanent pacemaker to prevent or treat symptoms that are related to a malfunctioning sinus node. A report from England (13) on 46 patients with sinus bradycardia concluded that most of these patients had a pathologic form of sinus bradycardia. Thirty-six of the 46 patients had syncopal
attacks or dizzy spells. Only one patient, however, required a permanent pacemaker to control frequent syncopal attacks. This report was published in 1971. In 1978, at least in the United States, most symptomatic patients would probably have received permanent pacemakers during the initial evaluation, other causes for symptoms having been excluded. In 1975, 13 times as many pacemakers per million people were inserted in the United States as in Great Britain. It may well be that not enough pacemakers are inserted in Great Britain, but quite possibly too many are inserted in this country. The sick sinus syndrome is becoming the single most common indication for permanent pacing, accounting for up to 50% of all inserted permanent pacemakers (2). Better definitions for permanent pacing in the sick sinus syndrome are needed. The mere presence of sick sinus syndrome as defined by the New York Heart Association Classification is not enough to make a decision for or against pacing. Our data suggest that sinus bradycardia as the sole manifestation of cardiac disease in the elderly patient has little effect on mortality. The overall 5-year survival of nonpaced patients with sinus bradycardia was even slightly higher than that in the general population (78% versus 72%). In viewing the good survival rate of the nonpaced patients, one must consider that most of these patients were either asymptomatic or had dizziness (without specific cause found). None of the patients had a severely compromised cardiac status, none was in functional Class 4, and only five were in functional Class 3 because of angina. Additionally, none of these patients had significant congestive heart failure. Only one of the 55 patients who had not received a pacemaker during the initial evaluation died suddenly as a consequence of possible rhythm disturbance. The patient was initially asymptomatic with a normal corrected sinus-node recovery time, had additional right bundle branch block and left axis deviation, and a prolonged His-to-ventricle time. Another eight of the 55 patients who were not paced initially developed syncope or dizziness, with slow heart rates during the follow-up period, and were treated with pacing. In each of these eight patients, the need for pacing was established by correlating symptoms with significant bradycardia on repeated monitoring. None of these patients suffered irreversible damage during the symptomatic episodes. Another four of the 55 patients had recurrent syncope (two patients) or recurrent dizziness (two patients) and refused permanent pacemakers. Continuous electrocardiographic monitoring clearly established that the bradycardic rhythm was responsible for symptoms. They have been followed now for 3, 3.5, 6, and 7 years, respectively, and are all still alive. The 5-year survival rate of 48 patients who were paced initially was 70%, not significantly different from that in the general population (72%). Our data do not permit us to state whether pacing symptomatic patients with sinus node problems prolongs life. The number of patients who had clearly abnormal and symptomatic sinus node disorders and who were not paced is too small to draw any conclusions from their outcome. A diseased sinus node Gann et al. • Sinus Bradycardia in Elderly Patients
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27
seems less likely to cause death, unlike complete heart block where 50% of unpaced patients are dead within 1 year (14). Our data suggest that there is no need for pacing in asymptomatic patients with sinus bradycardia, even if this appears to be a true manifestation of sick sinus syndrome. Patients with persistent heart rates below 40/min may be exceptions, but these patients rarely are asymptomatic. In the group of 11 asymptomatic patients with abnormal corrected sinus-node recovery time, eight eventually became candidates for permanent pacing because they became symptomatic or developed long periods of asystole. However, the interval from documentation of the abnormal sinus function to development of symptoms varied from a few months to as long as 6 years. None of the patients suffered irreversible damage or died as a consequence of the malfunctioning sinus node. Therefore we do not suggest routinely doing sinus-node recovery times in asymptomatic patients with sinus bradycardia. There is probably little disagreement that patients with abnormally functioning sinus nodes frequently have disease in the remainder of the conduction system. This has been confirmed in our study. Fifty-five percent of 103 patients had additional abnormalities of conduction in the atrioventricular node or interventricular conduction system. Therefore, if atrial pacing is considered for any patient, the rest of the conduction system should be initially evaluated and this mode of therapy used only if conduction through the atrioventricular node and interventricular conduction system is intact. Several reports have shown that the most useful test for detecting abnormal sinus node function is the sinusnode recovery time (10, 15-18). Two studies dealing with relatively small groups of patients did not find the sinusnode recovery time to be very helpful (19, 20). Additional tests such as measurement of sinoatrial conduction time, response to atropine, repetition of sinus-node recovery time after atropine, and evaluation of the first 10 beats after cessation of atrial pacing all have merit. We did not routinely use these additional tests when our study began and therefore will not comment further on their value. At present we may use any or all of these tests in selected patients. Persistent sinus bradycardia below 55 beats/min in the elderly patient frequently is an expression of malfunctioning sinus node. Is it therefore helpful to add a test that merely proves that the sinus node is truly diseased? Based on the findings in this study, we believe that an abnormal corrected sinus-node recovery time occurs only in patients with fairly advanced sinus node dysfunction. An abnormal corrected sinus-node recovery time did prove to be a very reliable confirmatory indication of which patient might need and benefit from permanent pacing. We believe that all patients with symptomatic sinus bradycardia and abnormal corrected sinus-node recovery time should be permanently paced. On the other hand, the finding of a normal corrected sinus-node recovery time does not exclude serious sinus node dysfunction. Measurement of a sinus-node recovery time has, in our opinion, been most helpful in symptomatic patients with 28
sinus bradycardia with heart rates above 40/min in whom no clear relation between symptoms and slow heart rate, even with continuous monitoring, could be established. This is a very common presentation. Assuming that no other medical reasons for symptoms could be found, an abnormal corrected sinus-node recovery time predicted that symptoms could be controlled with pacing in 100% of patients with syncope and 9 1 % of patients with dizziness. Measurement of corrected sinus-node recovery time in these patients may help shorten hospital stay substantially and make numerous costly 24-h electrocardiographic monitoring periods unnecessary. We should also consider the value of a sinus-node recovery time from a different point of view. One may suggest insertion of a permanent pacemaker in a patient with sinus bradycardia and symptoms if no other cause for the symptoms can be found. However, 40% of our patients with dizziness and 28% with syncope under the latter circumstances needed no pacemaker as determined by our follow-up time of 4.6 years. All of these were patients with normal corrected sinus-node recovery time. Therefore, the findings on a pacing study can be used to better separate those patients more likely to benefit symptomatically from pacing from those who would not. We confirm previous reports (5-8) that permanent pacing in properly selected patients frequently controls symptoms related to a diseased sinus node. Of 23 patients with syncope and permanent pacemaker insertion at the beginning of the study, only two continued to have symptoms, and of 17 patients with dizziness who were permanently paced, three remained symptomatic. Therefore, of 40 patients with sinus node dysfunction and symptoms who were permanently paced, only five continued to have some intermittent symptoms; 87.5% of patients became asymptomatic with pacing. From these findings, we suggest this approach for managing elderly patients with sinus bradycardia. 1. Asymptomatic sinus bradycardia—observe only. There is no need for prolonged monitoring. Persistent sinus bradycardia at rest below 40 beats/min may be an indication for permanent pacing in asymptomatic patients. However, patients are usually symptomatic at these slow rates. 2. Symptomatic sinus bradycardia—rule out other causes for symptoms and continue evaluation with 24-h electrocardiographic monitoring. A pacemaker is indicated if the patient becomes symptomatic during monitoring and has slow heart rates at the same time. Symptoms without severe bradycardia or periods of sinus arrest virtually exclude a diseased sinus node as the cause. Many of the patients who are monitored will not be symptomatic during the monitoring period. These patients should undergo electrophysiologic evaluation. An abnormal corrected sinus-node recovery time is clearly an indication for permanent pacing in the symptomatic patient. If a normal corrected sinus-node recovery time is present, we suggest further observation. Multiple 24-h recordings may be needed in these patients. Additional tests to measure sinus node function such as administration of atropine (21), measurement of sinus-node recovery time after
January 1979 • Annals of Internal Medicine • Volume 90 • Number 1
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atropine, conduction of the first 10 beats after cessation of pacing (22, 23), or measurement of intrinsic heart rates after administration of atropine and propanolol (24) may find other patients who need permanent pacing. • Requests for reprints should be addressed to Dietmar Gann, M.D.; Division of Cardiology, Mount Sinai Medical Center; Miami Beach, F L 33140. Received 8 May 1978; revision accepted 3 October 1978.
11. A N D E R S O N R P , B O N C H E K LI, G R U N K M E I E R GL,
L A M B E R T LE,
STARR A: The analysis and presentation of surgical results by actuarial methods. J Surg Res 16:224-230, 1974 12. Statistical Abstract of the United States, 1976, 97th ed. Washington, D.C., U.S. Bureau of the Census, 1976 13. ERAUS D, S H A W DB: Sinus bradycardia. Br Heart J 33:742-749, 1971 14. FRIEDBERG CK, DONOSO E, STEIN EG: Nonsurgical acquired heart block. Ann NY Acad Sci 111:835-847, 1964 15. STRAUSS HC, B I G G E R JT J R , SAROFF AL, G I A R D I N A EGV: Electro-
physiologic evaluation of sinus node function in patients with sinus node dysfunction. Circulation 53:763-776, 1976 16. T O Y A M A J, I T O A, S A W A D A K, T A N A H A S H I Y, T S U Z U K I J, W A T A N -
References 1. F E R R E R MI: The sick sinus syndrome. Its status after ten years (editorial). Chest 72:554-555, 1977 2. K A P L A N BM: Sick sinus syndrome (editorial). Arch Intern Med 138:28, 1978 3. B O W E R PJ: Sick sinus syndrome. Arch Intern Med 138:133-137, 1978 4. K A P L A N BM: The tachycardia-bradycardia syndrome. Med Clin North Am 60:81-89, 1976 5. KRISHNASWAMI V, GERACI AR: Permanent pacing in disorders of sinus node function. Am Heart J 89:579-585, 1975 6. C H O K S H I DS, M A S C A R E N H A S E, S A M E T P, C E N T E R S: Treatment of
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