Exercise-Provoked Block
Distal
Atrioventricular
similar episode 2 years ago. The resting electrocardiogram demonstrated sinus rhythm, a PR interval Saurabh K. Chokshi, MD, Joseph Sarmiento, MD, Jose Nazari, MD, of 0.18 secondand a completeright Thomas Mattioni, MD, Terry Zheutlin, MD, and Richard Kehoe, MD bundle branch block with a normal frontal plane axis (Figure 1). Coning unmasked serious underlying tinuous ambulatory monitoring for pontaneous or pacing-induced conduction system disease, which 72 hoursfailed to reveal evidencefor nonfunctional atrioventricular (AV) block occurring distal to the would have otherwise gone undetect- AVblock. An exercisestresstest was carried out usingthe modified Bruce His bundle recording site is associ- ed by routine ambulatory monitoring ated with a high probability of subse- and resting electrocardiograms. Sub- protocol. The patient had a resting quent syncope or progression to high sequent evaluation of their conduc- heart rate of 85 beatslmin. During stageIII of exercise testing, with the grade AV block. l Accordingly, a reli- tion systems by electrophysiologic increase in heart rate up to 110 able noninvasive method that could studies revealed marked prolongation of the HV interval and AV block beatslmin, 4:3 Mobitz type I secondpotentially unmask distal His-Purkinje block would be helpful in iden- distal to the His bundle in response to degreeAV block appeared.At sinus rates of 130 beatslmin, 3:2 AV block tifying patients in whom invasive rapid atria1 pacing. CASE 1: A 74-year-old woman was observed (Figure 2). Normal conduction system studies should be undertaken. We report 3 patients in had syncope while sitting at the din- anterograde conduction resumed at whom the occurrence of second-de- ner table. Her previous cardiac his- 2 minutes into the recovery period gree AV block during exercise test- tory was unremarkable except for a (sinus rate 98 beatslmin). No ST-T changes were provoked during the exercise test. Subsequent electrophysiologic studies demonstrated prolongation of the HV interval (85 ms) at rest (Figure 3A). During rapid atria1 pacing, 1:I conduction was maintained at rates up to 105 beats/ min. At an atria1 pacing rate of 1IO beatslmin (cycle length 545 ms), a 3:2 Mobitz type I second-degreeAV block distal to the His bundle was observed (Figure 3B). With pacing rate up to 120 beatslmin (cycle length 500 ms), a 3:2 AV block was noted (Figure 3C). The paced rate at which block appeared was identical to the sinus rate at which spontaneous block occurred during exercise FIGURE 1. Twelve-lead eketrocardiogramshowingnennal~planeaxisand testing. The patient received a percampleterightbundebranchblockincasel. manent dual chamber (DDD) pacemaker and has remained asymptomatic during 36 monthsoffollowup* CASE 2: A 53-year-old woman with biopsy-proven polymyositis was evaluated for episodic lightheadedness during exertion. The resting electrocardiogram revealed
S
FIGURE 2. Exe&e -am exerdse al an atrial rate 110 beats/mln; ink+adV~andarrowinleadVsincasel. 114
THE AMERICAN
JOURNAL
(leads II, VI and Vg) at&r 6 minutes of 43 AV con&c&m is shown by astehh
OF CARDIOLOGY
VOLUME
66
From the Section of Cardiology (Department of Medicine), Northwestern University Medical School, Chicago, Illinois. Dr. Chokshi is a Research Fellow of the American Heart Association, Massachusetts Affiliate, Needham, Massachusetts. His present address and address for reprints: Department of Cardiology, St. Elizabeth’s Hospital, 736 Cambridge Street, Boston, Massachusetts 02135. Manuscript received January 30,199O; revised manuscript received and accepted February 26, 1990.
TABLE
I Electrophysiologic
Correlation
of Exercise-Provoked
Distal
AtrioventriCUlar
Block EP Evaluatron
Study
Age (yr) & Sex
Klausche et al7 Freeman et ale Woelfel et al9
54, M 55, M 54, M
Peller et ali0 Present study
69, M 55, M 44, I= 74, F 53, F 69, M
AM = ambulatory
monltorlng.
Symptoms Dourness, Dizziness Palpitations Diuiness 0 Palpitation, Syncope Dizziness Dizziness
AVB = atrloventrlcular
sinus rhythm with first-degree AV block, left anterior divisional block and complete right bundle branch block. Forty-eight-hour ambulatory monitoring failed to reveal spontaneous second-degree AVblock. During an exercise stress test, at a sinus rate of 130 beatslmin, a 2:1 Mobitz type I second-degree AV block occurred. During the subsequent invasive electrophysiologic study, a 2:l second-degree block distal to the His bundle developed in response to atrial pacing at a rate of 120 beats/min. Implantation of a permanent pacemaker led to resolution of symptoms. CASE 3: A 69-year-old white man was seen for progressive lightheadedness. On cardiac monitoring, he was found to be in a third-degree heart block with a ventricular rate of 22 beats/min (sinus rate I1 0 beats/ min). A temporary transvenous pacemaker was placed for 72 hours. He evolved a small, anterior wall, non-Q-wave myocardial infarction. Over the next 36 hours, the high grade AVblock completely resolved. Cardiac catheterization revealed total occlusion of the distal right coronary artery, 50% stenosis of the left anterior descending artery, 40% stenosis of the left circumflex artery and mild apical hypokinesis of the left ventricle. On exercise stress test, a 2:l AV block was demonstrated at sinus rates of 110 beatslmin; however, a thallium scan failed to reveal perfusion defects. The subsequent electrophysiologic studies revealed a prolonged HV interval (90 ms) and 2:l AT/block distal to the His bundle during atria1 pacing at rates of 110 beatslmin. The patient received a
RBBB angrna
dizziness
+ + 0 + + 0 +
+ 0 block, EP = electrophystologlc,
FIGURE rhythm
AM (beats/min)
El-r (beats/min)
Type II 2:l
AVB (130) -
No AVB Type II 2:l AVB (148) No AVB No AVB No AVB E T T = exercw
treadmill
44 50 70 65
2:l AVB (140) 2:l AVB(125) 3:2 AVB (125) 2:l AVB (140) 2:l AVB (140) 2:l AVB (148) 4:3AVB(llO) 2:l AVB(130) 2:l AVB (110)
test, RBBB = right bundle
3. Surface and intracadiac electrocanliographic (A) and atrial pacing at rates of 110 beatdmin
in~re1.A,duingd~m~,1:lAVconduelion~~.TheHV
Atrial Pacing (beats/min)
y:s,
2:l AVB(100) 3:2AVB(llO) 2: 1 AVB (85) 2:l AVB(170) 2:l AVB (120) 3:2AVB(120) 4:3 AVB (110) 2:l AVB (120) 2:1AVB(llO)
45 85 90
75 branch
b&k:
+ = present:
0 = absent,
tracings &&ng &w (B) and 120 beats/min
(C)
intewal is con&ant 1SSms. B,~atriatpmhgatcydehgth545ms, S~AVbkdcdstdtooHb~po~isrcen(a~w~ C,ataNgher atrial pacing rate (cycle+ knglh 500),3P AV block (arrow) distal to His is no~.A=rigMabialdatkction;H=Hb~detlection;HBE=H~kndk zmaErsHRA = high rtght atrtal ektrogram; V = dght venbidar deflection represent duration in ms.
THE AMERICAN
JOURNAL
OF CARDIOLOGY
JULY
1, 1990
.
115
dual chamber pacemaker and has remained asymptomatic. The diagnosis of conduction disease in 1 or 2 of the 3 fascicles suggests an impaired safety margin for AV conduction.’ A wealth of anatomic and clinical studies supports a relation between intraventricular conduction disturbance and progression to high grade or complete AV block.2,3 Progression to complete AV block may be sudden or may occur episodically and could result in sudden death or syncope. The ability to recognize patients with intraventricular conduction disturbance at high risk for progression to complete AV block is important; they could benefit from prophylactic pacemaker therapy. Standard 12-lead electrocardiography has a limited value in identification of such patients.3 Ambulatory monitoring has also been ineffective in unmasking high grade AV block, especially in the early stage of progression. All 3 patients reported here failed to demonstrate AV block on ambulatory monitoring despite 72 hours of recording. This may be explained by the fact that none of the patients accelerated their heart rates during activities that could have induced AV block. Exercise-induced AV block is uncommonly observed.4,5 When present, it carries a significant value in identifying patients with a higher risk for progression to complete AV block. Fewer than 25 cases of exercise-induced AV block occurring in patients with normal AV conduction have been reported.4-10 Since AV conduction should be enhanced as a result of exercise-related vagal with-
116
THE AMERICAN
JOURNAL
drawal and increased sympathetic drive, AV block has been shown to improve or resolve during exercise. Several investigators have postulated that the site of AV block occurring during exercise is more likely to be localized to the distal His-Purkinje system rather than the AV node because the His-Purkinje system is relatively insensitive to autonomic modulation, and it has a relatively fKed effective refractory period that fails to decrease sufficiently with decreasing atria1 cycle length to permit 1: 1 AV conduction. In patients with bifascicular block and syncope, utility of electrophysiologic studies has been well established.’ Both prolongation of the HV interval at rest and demonstrable block distal to the His bundle during rapid atria1 stimulation are widely used to stratify patients at a higher risk of developing complete AV block.7-10 Previously published studies have established the utility of these markers. For example, in the study by Dhingra et al,’ 15 of 496 patients with chronic bifascicular block developed distal block during rapid atria1 pacing; during follow-up, complete AV block developed in 8 of the 15 patients and 2 died suddenly. In addition to the 3 patients reported here, in only 6 other cases have exercise-induced findings of AV block been correlated with invasive electrophysiologic data (Table I).7-10 In patients with coronary artery disease, reversible, transient seconddegree or high grade AV block may occur due to exercise-induced ischemia6 or secondary to coronary spasm. It is important to note that clinical or angiographic evidence for
OF CARDIOLOGY
VOLUME
66
coronary artery disease was present in only 1 of our 3 patients; however, myocardial ischemia, based on ST-T segment changes, was absent in the remaining 2. In summary, the 3 patients we report add to the limited body of published data regarding the significance of exercise-provoked AV block. Since the patients with symptoms of lightheadedness or syncope and exercise-induced AV block are likely to have a block distal to His, permanent pacing seems justified. 1. Dhingra RC, Wyndham C, Bauernfeind R, Swiryn S, Deedwania PC, Smith T, Dews P, Rosen KM. Significance of block distal to the His bundle induced bv atria1 oacine in the oatients with chronic bifascicular bloci C&lotion’1 979,60:1455-1464. 2. Lev M. The normal anatomy of the conduction system and its pathology in atrioventricular block. Ann NY Acad Sci 1964:ll It81 7-821, 3. Lasser RP, Halt JI, Freidberg CK. Relationship of right bundle branch block and marked left axis deviation (with left pa&al and per&infarction block) to complete heart block and syncope. Circulation 1968; 37:429-437. 4. Baskt A, Goldberg B, Schamroth L. Significance of exercise-induced second degree atrioventricular block. Br Heart .I 1975;37:984-986. 5. Mouloooulos SD. Darsinos J. Sideris DA. Atrioventricular block response to exercise and intraventricular conduction at rest. Br Heart J 1972;34:9981004. 6. Rozanski JJ, Castellanos A, Sheos D, Pozen R, Myerberg RJ. Paroxysmal second-degree atrioventricular block induced by exercise. Heart Lung 1980,9:887-890. 7. Klausche D, Roskamm H. Tachycardia dependent second-degree A-V block in a patient with right bundle branch block. / Electrocardiol 1987;20:169175. 8. Freeman G, Hwang MW, Danowiz J, Moran JF, Gunnar RM. Exercise-induced “Mobitz type II” second degree AV block in a patient with chronic bifascicular block (right bundle branch block and left anterior hemiblock). J Ekctrocardiol 1984;17:409412. 9. Woelfel AK, Simpson RJ, Gettea LS, Foster JR. Exercise-induced distal atrioventricular block. JACC 1983;2:578-581. 10. Peller OG, Moses JW, Kligfield P. Exerciseinduced atrioventricular block: report of three cases. Am Heart J 1988:115:1315-1317.
Distal
Atrioventricular
similar episode 2 years ago. The resting electrocardiogram demonstrated sinus rhythm, a PR interval Saurabh K. Chokshi, MD, Joseph Sarmiento, MD, Jose Nazari, MD, of 0.18 secondand a completeright Thomas Mattioni, MD, Terry Zheutlin, MD, and Richard Kehoe, MD bundle branch block with a normal frontal plane axis (Figure 1). Coning unmasked serious underlying tinuous ambulatory monitoring for pontaneous or pacing-induced conduction system disease, which 72 hoursfailed to reveal evidencefor nonfunctional atrioventricular (AV) block occurring distal to the would have otherwise gone undetect- AVblock. An exercisestresstest was carried out usingthe modified Bruce His bundle recording site is associ- ed by routine ambulatory monitoring ated with a high probability of subse- and resting electrocardiograms. Sub- protocol. The patient had a resting quent syncope or progression to high sequent evaluation of their conduc- heart rate of 85 beatslmin. During stageIII of exercise testing, with the grade AV block. l Accordingly, a reli- tion systems by electrophysiologic increase in heart rate up to 110 able noninvasive method that could studies revealed marked prolongation of the HV interval and AV block beatslmin, 4:3 Mobitz type I secondpotentially unmask distal His-Purkinje block would be helpful in iden- distal to the His bundle in response to degreeAV block appeared.At sinus rates of 130 beatslmin, 3:2 AV block tifying patients in whom invasive rapid atria1 pacing. CASE 1: A 74-year-old woman was observed (Figure 2). Normal conduction system studies should be undertaken. We report 3 patients in had syncope while sitting at the din- anterograde conduction resumed at whom the occurrence of second-de- ner table. Her previous cardiac his- 2 minutes into the recovery period gree AV block during exercise test- tory was unremarkable except for a (sinus rate 98 beatslmin). No ST-T changes were provoked during the exercise test. Subsequent electrophysiologic studies demonstrated prolongation of the HV interval (85 ms) at rest (Figure 3A). During rapid atria1 pacing, 1:I conduction was maintained at rates up to 105 beats/ min. At an atria1 pacing rate of 1IO beatslmin (cycle length 545 ms), a 3:2 Mobitz type I second-degreeAV block distal to the His bundle was observed (Figure 3B). With pacing rate up to 120 beatslmin (cycle length 500 ms), a 3:2 AV block was noted (Figure 3C). The paced rate at which block appeared was identical to the sinus rate at which spontaneous block occurred during exercise FIGURE 1. Twelve-lead eketrocardiogramshowingnennal~planeaxisand testing. The patient received a percampleterightbundebranchblockincasel. manent dual chamber (DDD) pacemaker and has remained asymptomatic during 36 monthsoffollowup* CASE 2: A 53-year-old woman with biopsy-proven polymyositis was evaluated for episodic lightheadedness during exertion. The resting electrocardiogram revealed
S
FIGURE 2. Exe&e -am exerdse al an atrial rate 110 beats/mln; ink+adV~andarrowinleadVsincasel. 114
THE AMERICAN
JOURNAL
(leads II, VI and Vg) at&r 6 minutes of 43 AV con&c&m is shown by astehh
OF CARDIOLOGY
VOLUME
66
From the Section of Cardiology (Department of Medicine), Northwestern University Medical School, Chicago, Illinois. Dr. Chokshi is a Research Fellow of the American Heart Association, Massachusetts Affiliate, Needham, Massachusetts. His present address and address for reprints: Department of Cardiology, St. Elizabeth’s Hospital, 736 Cambridge Street, Boston, Massachusetts 02135. Manuscript received January 30,199O; revised manuscript received and accepted February 26, 1990.
TABLE
I Electrophysiologic
Correlation
of Exercise-Provoked
Distal
AtrioventriCUlar
Block EP Evaluatron
Study
Age (yr) & Sex
Klausche et al7 Freeman et ale Woelfel et al9
54, M 55, M 54, M
Peller et ali0 Present study
69, M 55, M 44, I= 74, F 53, F 69, M
AM = ambulatory
monltorlng.
Symptoms Dourness, Dizziness Palpitations Diuiness 0 Palpitation, Syncope Dizziness Dizziness
AVB = atrloventrlcular
sinus rhythm with first-degree AV block, left anterior divisional block and complete right bundle branch block. Forty-eight-hour ambulatory monitoring failed to reveal spontaneous second-degree AVblock. During an exercise stress test, at a sinus rate of 130 beatslmin, a 2:1 Mobitz type I second-degree AV block occurred. During the subsequent invasive electrophysiologic study, a 2:l second-degree block distal to the His bundle developed in response to atrial pacing at a rate of 120 beats/min. Implantation of a permanent pacemaker led to resolution of symptoms. CASE 3: A 69-year-old white man was seen for progressive lightheadedness. On cardiac monitoring, he was found to be in a third-degree heart block with a ventricular rate of 22 beats/min (sinus rate I1 0 beats/ min). A temporary transvenous pacemaker was placed for 72 hours. He evolved a small, anterior wall, non-Q-wave myocardial infarction. Over the next 36 hours, the high grade AVblock completely resolved. Cardiac catheterization revealed total occlusion of the distal right coronary artery, 50% stenosis of the left anterior descending artery, 40% stenosis of the left circumflex artery and mild apical hypokinesis of the left ventricle. On exercise stress test, a 2:l AV block was demonstrated at sinus rates of 110 beatslmin; however, a thallium scan failed to reveal perfusion defects. The subsequent electrophysiologic studies revealed a prolonged HV interval (90 ms) and 2:l AT/block distal to the His bundle during atria1 pacing at rates of 110 beatslmin. The patient received a
RBBB angrna
dizziness
+ + 0 + + 0 +
+ 0 block, EP = electrophystologlc,
FIGURE rhythm
AM (beats/min)
El-r (beats/min)
Type II 2:l
AVB (130) -
No AVB Type II 2:l AVB (148) No AVB No AVB No AVB E T T = exercw
treadmill
44 50 70 65
2:l AVB (140) 2:l AVB(125) 3:2 AVB (125) 2:l AVB (140) 2:l AVB (140) 2:l AVB (148) 4:3AVB(llO) 2:l AVB(130) 2:l AVB (110)
test, RBBB = right bundle
3. Surface and intracadiac electrocanliographic (A) and atrial pacing at rates of 110 beatdmin
in~re1.A,duingd~m~,1:lAVconduelion~~.TheHV
Atrial Pacing (beats/min)
y:s,
2:l AVB(100) 3:2AVB(llO) 2: 1 AVB (85) 2:l AVB(170) 2:l AVB (120) 3:2AVB(120) 4:3 AVB (110) 2:l AVB (120) 2:1AVB(llO)
45 85 90
75 branch
b&k:
+ = present:
0 = absent,
tracings &&ng &w (B) and 120 beats/min
(C)
intewal is con&ant 1SSms. B,~atriatpmhgatcydehgth545ms, S~AVbkdcdstdtooHb~po~isrcen(a~w~ C,ataNgher atrial pacing rate (cycle+ knglh 500),3P AV block (arrow) distal to His is no~.A=rigMabialdatkction;H=Hb~detlection;HBE=H~kndk zmaErsHRA = high rtght atrtal ektrogram; V = dght venbidar deflection represent duration in ms.
THE AMERICAN
JOURNAL
OF CARDIOLOGY
JULY
1, 1990
.
115
dual chamber pacemaker and has remained asymptomatic. The diagnosis of conduction disease in 1 or 2 of the 3 fascicles suggests an impaired safety margin for AV conduction.’ A wealth of anatomic and clinical studies supports a relation between intraventricular conduction disturbance and progression to high grade or complete AV block.2,3 Progression to complete AV block may be sudden or may occur episodically and could result in sudden death or syncope. The ability to recognize patients with intraventricular conduction disturbance at high risk for progression to complete AV block is important; they could benefit from prophylactic pacemaker therapy. Standard 12-lead electrocardiography has a limited value in identification of such patients.3 Ambulatory monitoring has also been ineffective in unmasking high grade AV block, especially in the early stage of progression. All 3 patients reported here failed to demonstrate AV block on ambulatory monitoring despite 72 hours of recording. This may be explained by the fact that none of the patients accelerated their heart rates during activities that could have induced AV block. Exercise-induced AV block is uncommonly observed.4,5 When present, it carries a significant value in identifying patients with a higher risk for progression to complete AV block. Fewer than 25 cases of exercise-induced AV block occurring in patients with normal AV conduction have been reported.4-10 Since AV conduction should be enhanced as a result of exercise-related vagal with-
116
THE AMERICAN
JOURNAL
drawal and increased sympathetic drive, AV block has been shown to improve or resolve during exercise. Several investigators have postulated that the site of AV block occurring during exercise is more likely to be localized to the distal His-Purkinje system rather than the AV node because the His-Purkinje system is relatively insensitive to autonomic modulation, and it has a relatively fKed effective refractory period that fails to decrease sufficiently with decreasing atria1 cycle length to permit 1: 1 AV conduction. In patients with bifascicular block and syncope, utility of electrophysiologic studies has been well established.’ Both prolongation of the HV interval at rest and demonstrable block distal to the His bundle during rapid atria1 stimulation are widely used to stratify patients at a higher risk of developing complete AV block.7-10 Previously published studies have established the utility of these markers. For example, in the study by Dhingra et al,’ 15 of 496 patients with chronic bifascicular block developed distal block during rapid atria1 pacing; during follow-up, complete AV block developed in 8 of the 15 patients and 2 died suddenly. In addition to the 3 patients reported here, in only 6 other cases have exercise-induced findings of AV block been correlated with invasive electrophysiologic data (Table I).7-10 In patients with coronary artery disease, reversible, transient seconddegree or high grade AV block may occur due to exercise-induced ischemia6 or secondary to coronary spasm. It is important to note that clinical or angiographic evidence for
OF CARDIOLOGY
VOLUME
66
coronary artery disease was present in only 1 of our 3 patients; however, myocardial ischemia, based on ST-T segment changes, was absent in the remaining 2. In summary, the 3 patients we report add to the limited body of published data regarding the significance of exercise-provoked AV block. Since the patients with symptoms of lightheadedness or syncope and exercise-induced AV block are likely to have a block distal to His, permanent pacing seems justified. 1. Dhingra RC, Wyndham C, Bauernfeind R, Swiryn S, Deedwania PC, Smith T, Dews P, Rosen KM. Significance of block distal to the His bundle induced bv atria1 oacine in the oatients with chronic bifascicular bloci C&lotion’1 979,60:1455-1464. 2. Lev M. The normal anatomy of the conduction system and its pathology in atrioventricular block. Ann NY Acad Sci 1964:ll It81 7-821, 3. Lasser RP, Halt JI, Freidberg CK. Relationship of right bundle branch block and marked left axis deviation (with left pa&al and per&infarction block) to complete heart block and syncope. Circulation 1968; 37:429-437. 4. Baskt A, Goldberg B, Schamroth L. Significance of exercise-induced second degree atrioventricular block. Br Heart .I 1975;37:984-986. 5. Mouloooulos SD. Darsinos J. Sideris DA. Atrioventricular block response to exercise and intraventricular conduction at rest. Br Heart J 1972;34:9981004. 6. Rozanski JJ, Castellanos A, Sheos D, Pozen R, Myerberg RJ. Paroxysmal second-degree atrioventricular block induced by exercise. Heart Lung 1980,9:887-890. 7. Klausche D, Roskamm H. Tachycardia dependent second-degree A-V block in a patient with right bundle branch block. / Electrocardiol 1987;20:169175. 8. Freeman G, Hwang MW, Danowiz J, Moran JF, Gunnar RM. Exercise-induced “Mobitz type II” second degree AV block in a patient with chronic bifascicular block (right bundle branch block and left anterior hemiblock). J Ekctrocardiol 1984;17:409412. 9. Woelfel AK, Simpson RJ, Gettea LS, Foster JR. Exercise-induced distal atrioventricular block. JACC 1983;2:578-581. 10. Peller OG, Moses JW, Kligfield P. Exerciseinduced atrioventricular block: report of three cases. Am Heart J 1988:115:1315-1317.
