Intracardiac electrography and young adults
in children
Paul C. Gillette, M.D. Milton J. Reitman, M.D. Howard P. Gutgesell, M.D. Thomas A. Vargo, M.D. Charles E. Mullins, M.D. Dan G. McNamara, M.D. Houston, Texas
Intracardiac electrograms (IE) recorded with electrode catheters are a useful adjunct to surface electrocardiography in the interpretation of conduction disturbances and arrhythmias in adults. Giraud’ was the first to record the His bundle potential (HBP) with catheter electrodes in humans; he recorded unipolar electrograms in children with several forms of congenital heart disease. Watson, Emslie-Smith, and Lowe recorded the HBP in one child with Ebstein’s disease in 1967 using the same technique. This technique was then modified and popularized in 1969 by Scherlag and others3 who recorded bipolar His bundle electrograms @IBE) with band passage set at 40 and 500 Hz. Several recent studies in children have found conflicting variations in the lengths of conduction intervals with age.4-7 The purpose of this study was (1) to determine the normal intervals associated with conduction of the sinus node impulse to the ventricular myocardium in infants and children and changes in these intervals related to age and to compare these values with those measured in normal adults, and (2) to study abnormalities of impulse formation and conduction in children with conduction disturbances and in patients receiving digitalis. From the Section lege of Medicine,
of Cardiology, Department and the Texas Children’s
Supported in part by Grant No. HL6756 of Health, United States Public Health States Public Health Grant RR-00166 Research Branch, National Institutes Received Reprint Texas
36
for publication requests: Children’s
Dr. Paul Hospital,
April
of Pediatrics, Baylor Hospital, Houston.
from the National Service, and in part from the General of Health.
Col-
Institutes by United Clinical
6, 1974.
C. Gillette, Section of Pediatric Cardiology, 6621 Fannin St., Houston, Texas 77026.
Methods Patients. The 158 subjects studied ranged in age from three days to 33 years and in weight from two to 70 kilograms. These cases represent the first 158 consecutive attempts to record the HBP in our institution. All but three subjects, who were studied primarily for evaluation of arrhythmias, underwent diagnostic cardiac catheterization for determination of an anatomic defect and hemodynamic abnormality. “Normal” group. Included among the 158 patients studied were 85 (ages, three days to 29 years) in whom the surface electrocardiogram 1ECG) showed normal conduction. Patients who had intracardiac surgery were excluded from this “normal” group. Twenty-two of the 85 patients were taking digitalis prior to the study; none of these had clinical or electrocardiographic signs of toxicity nor were any of the patients receiving other medications known to alter conduction. Digitalis was withheld for 24 hours prior to the study as part of the preparation for catheterization. The cardiovascular lesions documented by cardiac catheterization in these 85 patients are listed in Table I. Abnormal group. Of the 158 patients, 43 with arrhythmias or conduction disturbances shown by surface ECG were evaluated to determine the effect of these abnormalities on the conduction intervals. The remaining 30 subjects could not be included into either the normal group or any of the specific groups of abnormalities being studied. These subjects are, therefore, included in neither the normal nor the abnormal groups, but are in-
January,
1975, Vol. 89, No. 1, pp. 36-44
Intracardiac
electrography
in children and young adults
Fig. 1. Normal His bundle electrogram MBE) from a lo-month-old child with a normal heart. From top to bottom: Lead II of the surface electrocardiogram; HBE with 1 mm. interelectrode distance: and HBE with 11 mm. interelectrode distance.
eluded in the general statistics such as the success rate. Many of these cases had undergone open-heart surgery. Catheterization techniques. Patients over two months of age were sedated with intramuscular meperidine hydrochloride (1.0 mg. per pound), promethazine hydrochloride (0.25 mg. per pound), and chlorpromazine, (0.25 mg. per pound) one hour before study. The patient and all electrical equipment were securely grounded. The catheter electrodes were connected to an Electronics for Medicine photographic recorder by way of a junction box. Surface ECG’s and IE were recorded simultaneously using frequency band widths of 0.1 to 20 Hz. and 40 to 500 Hz., respectively, at paper speeds of 100 or 200 mm. per second with one-second time lines. Bipolar and tripolar electrode catheters (sizes 4 through 7 French) with interelectrode distances ranging from 1 mm. to 10 mm. were introduced through the femoral or saphenous vein. In children over 10 pounds, the percutaneous sheath technique was used,8 while in smaller infants a saphenous vein cutdown was performed. In a few cases, HBE’s were recorded from the left ventricle with electrode catheters introduced through a sheath previously placed in a femoral artery. When necessary, two electrode catheters were introduced percutaneously either into the same vein or into each of the femoral veins. The electrode catheter was guided with fluoroscopy into the right ventricular apex and
American Heart Journal
Table I. Cardiovascular
normal
conduction
defects in subjects with by surface ECG
Normal structure and hemodynamics Ventricular-septal defect D-transposition of the great arteries Patent ductus arteriosus Pulmonic stenosis Tetralogy of Fallot Aortic stenosis Atrial-septal defect (secunduml Coarctation of the aorta Miscellaneous
19 15 12 I I I 4 4 3 - I
Total
85
then slowly withdrawn with clockwise rotation until the His bundle deflection was seen on the oscilloscope (Fig. 1). Several potentials were recorded sequentially in the low right atrium-toventricle (LRA-V) interval but the potential following the low right atria1 (LRA) deflection which was farthest from the ventricular electrogram was designated the HBP. In some cases, the HBP was recorded from the junction of the left ventricle and left atrium either with the catheter advanced across an atrial-septal defect or patent foramen ovale or by placement of the catheter in a retrograde manner across the aortic valve or into the posterior sinus of Valsalva in the aortic root. To record the high right atria1 (HRA) potential, the catheter
37
Gillette
et al.
Table II. Mean intervals
in subjects with normal
conduction
by surface electrocardiogram Congenital heart disease 66 patients
Interval
Normal hemodynamics (19 patiwlts)
HR PR P-LRA LRA-H H-V Rb-V
107 f 125 f 14 f 73 f 38f 25f
< 2-year-old (21 patients)
25 18 10 17 7 7
136 f 124 f 15 f 72 f 36+ 24f
2-IO-year-old (43 patients)
23 19 12 15 8 8
109 133 18 75 41 26
f f f f f f
> 1 O-year-old (14 patients)
20 19 16 19 10 10
91 130 13 79 42 28
f f f f f f
20 10 12 17 11 11
All intervals are the mean value in milliseconds f ISEM. HR, heart rate. P, beginning of P-wave in surface ECG. LRA, low right atrium. H, His bundle. Rb, right bundle branch. V, ventricle.
Table Ill. Conduction
abnormalities mias studied in 43 subjects First-degree A-V block Second-degree A-V block Third-degree A-V block RBBB Short PR Premature beats
and arrhyth11 2 5 18 6 4 46
was positioned at the junction of the superior vena cava and right atrium. Conduction intervals. The intervals measured and their anatomic correlates are defined below: P-LRA. Beginning of P-wave on simultaneously recorded surface ECG to first atria1 deflection on the HBE. This estimates the conduction time from the sinoatrial node to atrioventricular (A-V) node. HRA-LRA. First rapid deflection on the HRA electrogram to first rapid deflection of the LRA electrogram. This allows a more precise estimate of conduction from the area of the sinoatrial node to the area of the A-V node than does the P-LRA interval. LRA-H. First rapid deflection of LRA electrogram to first rapid deflection of HBP. This represents conduction time through the A-V node. H-V. First rapid deflection of HBP to the earliest ventricular activity either on surface ECG or IE. This represents conduction time from the His bundle to the ventricular myocardium. R&V. First rapid deflection of a potential after the HBP to the earliest ventricular activity. This
38
represents conduction time from the right dle to the ventricular myocardium.
bun-
Results
The His bundle potential was identified in 156 out of 158 patients in whom this technique was attempted. HBP’s were recorded in virtually all congenital heart lesions including complex lesions such as transposition of the great arteries before and after surgical correction, ventricular inverserion, tetralogy of Fallot, endocardial cushion defects, and tricuspid atresia, as well as simpler lesions. The right bundle branch potential and the right bundle-to-ventricle interval were also measured in 45 patients. There were no complications. “Normal” group. Table II lists the values for several conduction intervals determined from the IE in 85 subjects with normal conduction on the surface ECG. Diagnostic catheterization confirmed the presence of a congenital cardiac defect in 66 of these subjects and proved the heart to be structurally normal in the remaining 19 subjects. Statistical analysis of the conduction intervals by Student’s t-test showed no statistically significant difference between intervals measured in subjects with structurally normal hearts and in those subjects with congenital heart disease. No statistical differences were found among the three age groups, nor between the patients who had received digitalis and those who had not. Abnormal group. The types of conduction abnormalities or arrhythmias found in the 43 subjects with abnormal surface ECG are listed in Table III. First-degree A-V block. The conduction inter-
January,
1975, Vol. 89, No. 1
Intracardiac Table IV. Intervals
in subjects with first-degree
electrography in children and young adults
atrioventricular
block QRS
PR
HR Age fjTS.)
duration
P-LRA
p/o VSD T/F Complex ASDI p/o ASD-VSD p/o ASD I VI, DILV ASDI p/o ASD I T/F p/o common
msec. 175 210 160 200 200 197 250 200 175 200 225
107 100 125 100 85 72 80 109 110 133 100
ventricle
p/o, postoperative. VSD, ventricular-septal double-inlet left ventricle.
Table V. Intervals
H-V IIlrIz
DiilglUWiS
22112 2 18112 2 8 10 21 7 12 4 5
LRA-H
defect. T/F, tetralogy
120 90 95 125 120 120 100 115 110 96 125
of Fallot. ASD I, ostiurn primurn
in subjects with pre-excitation
0 0 35 0 5 7 0 30 30 30 25 etrial-septal
Table VI. Intervals
135 180 105 155 140 135 150 135 70 100 170
40 30 20 45 55 55 100 40 75 70 30
defect. VI, ventricular
inversion.
DILV,
in subjects with right bundle
branch block QRS
HR
Associated diugnosis
8 m. f5yr. 2 mo. 20 mo.
2 yr. 20 mo. AS, aortic defect.
Normal hemodynamics AS, PS Left atrial rhahdomyoma Pompa’s disease Normal hemodynamics VSD stenosis.
PS. pulmonic
PR LRA-H
H-V HR
msec. 120
83
110
95
15
110 70
80 80
105 80
100 50
0 30
80 90
129 160
90 75
35 30
30 35
80
100
100
55
35
stenosis.
VSD, ventricular-septal
vals measured in 11 subjects with first-degree A-V block, none of whom were taking cardioactive drugs, are shown in Table IV. A prolonged LRA-H interval was demonstrated in eight of the 11 subjects, a prolonged H-V interval in two subjects, and prolongation of both intervals in one subject. Third-degree A-V block Congenital complete A-V block was present in five of the 43 subjects with arrhythmias. Three of these five subjects also had ventricular inversion; in these cases, the block was found below the bundle of His potential. In the fourth subject, the block was above the bundle of His. In the fifth subject, the site of block was in the bundle of His indicated by the occurrence of two separate His potentials (“split His”), one following atria1 deflection, and the
American Heart Journal
Age (yr.) 12 3 4 22112 8 17 18 4 8 33 11 4 3 12 14 6 4% 5
PR
Diagrwsis p/o T/F PPH p/o T/F p/o VSD p/o ASD-VSD p/o truncus p/o VSD p/o T/F p/o truncua p/o T/F p/o TIP p/o T/F p/o DORV (dextrocardia) p/o T/F p/o VSD p/o T/F p/o T/F p/o common ventricle
LRA-H
H-V
Rb-V
10 -
malee. 83 58 95 107 85 90 85 100 95 86 80 90 105
170 140 120 175 200 180 150 170 150 130 105 140 115
115 100 90 135 140 85 80 110 125 85 60 100 75
55 40 30 40 55 45 45 60 55 45 50 45 35
120 140 83 170 85 125 110 150 100 225
60 90 75 80 170
45 45 43 48 30
10 30 25 25 35 30 10
p/o, postoperative. T/F, tetralogy of Fallot. PPH. primary pulmonary hypertension. VSD, ventricular-septal defect. ASD. atrial-septal defect. DORV, double-outlet right ventricle.
other preceding
ventricular
depolarization
(Fig.
2). Short P-R interval. Six subjects with short P-R
intervals were studied (Table V). Shortening of the H-V interval was found in two subjects with QRS prolongation (Wolff-Parkinson-White syn-
39
Gillette
et al.
Fig. 2. His bundle electrogram from a child with congenital complete heart block demonstrating a “split His” potential; that is, His potentials following each low right atrial potential and before each ventricular electrogram indicative of block in the common bundle of His.
Fig. 3. His bundle electrogram of tachycardia demonstrating bypass.
in a 20-month-old child with a VSD, short PR interval, normal QRS, and a history shortened atrial to His bundle conduction consistent with atrioventricular node
drome) and shortening of the LRA-H interval was found in the four subjects with normal QRS duration and morphology (Fig. 3). Right bundle branch block. The surface ECG indicated the presence of right bundle branch block pattern in 18 subjects; none had associated left anterior hemiblock. In 17 subjects, the bundle branch block pattern had resulted from cardiac surgery. The H-V interval in all 18 cases was within two standard deviations of the normal mean. The right bundle branch electrogram was identifiable in only seven cases; the Rb-V interval was normal in each of these cases (Fig. 4). Premature complexes or paroxysmal tachycardia. IE were recorded in four subjects to inves-
40
tigate multiple premature complexes or paroxysmal tachycardia of obscure origin. In one case, both atria1 and His bundle potentials were found before each premature complex indicating an atria1 origin. In another case, only His potentials were identified and the H-V intervals were 10 msec. shorter than conducted beats, indicating origin of the premature beats to be in a bundle branch. In the third case, no atria1 or His potentials were recorded before the premature beats, whereas they were recorded during comparable time before conducted beats, showing the premature beats arose in the ventricular myocardium. The fourth child had normal intervals both at rest and with multiple premature atria1 con-
January, 1975, Vol. 89, No. 1
Intracardiac
,_,
‘id
*
electrography
in children and young adults
i
’
Fii. A His bundle and right bundle branch potentials recorded in a three-year-old after correction of double outlet right ventricle with dextrocardia at which time a right bundle branch block pattern was induced on her electrocardiogram.
Fig. 5. His bundle electrograms from a six-month-old patient with recurrent intervals during sinus rhythm but no His potential during tachycardia.
American Heart Journal
tachycardia demonstrating
normal
41
Gillette
et al.
Fig. 6, His bundle electrogram from a la-year-old girl six years after surgical correction cushion defect demonstrating a prolonged H-V interval of 70 milliseconds.
tractions, but during a paroxysm of tachycardia, no His potential could be found, indicating along with the A-V disassociation and wide QRS complexes, either ventricular tachycardia or nodal tachycardia with extra-Hisian pre-excitation (Fig. 5). The findings in the other 30 subjects were varied. Twelve of the subjects had undergone Mustard operation and their conduction intervals were normall Nine patients had ostium primum atrial-septal defect and, with the exception of those who had undergone surgery, the conduction intervals were also normal. Studies were performed in two other subjects to delineate the type of A-V block present following cardiac surgery. One eight-year-old boy who had transient complete A-V block after surgery to remove a subvalvular pulmonic stenosis associated with ventricular inversion had normal intervals 10 days after surgery. The other subject with transient complete A-V block postoperatively was studied six years after surgery because of syncopal attacks. Despite a sinus rhythm, this patient had a prolonged H-V interval (Fig. 61. Discussion
Intracardiac electrography is useful in interpreting and treating certain obscure arrhythmias and conduction disturbances in adults,lT g especially in determining the site and type of A-V block, the localization of the focus for tachyarrhythmias, and the type of accelerated A-V conduction.1° Studies in children have been concerned with congenital heart block,” surgical heart block,12, Mobitz Type II block,13 and electrophysiologic abnormalities after Mustard operation.14 There are several reports of normal con42
of an endocardial
duction intervals for adults and three reports of conduction intervals in children with congenital heart disease with and without abnormal surface ECG’S.~-~ The effect of digitalis on conduction has not been studied in children. It is necessary to differentiate the right bundle branch potential from the HBP since confusing the HBP with the right bundle branch potential would give a falsely small value for the H-V interval. Other investigators have accomplished this either by His bundle pacing or by evaluating the response of the conduction intervals to right atria1 pacing. Neither of these methods are completely reliable and both introduce possible additional hazards to the patient, i.e., high milliamperage needed for His bundle pacing and additional catheter for atria1 pacing. We, therefore, used a different method to identify the His bundle potential. We withdrew the catheter slowly across the tricuspid valve while recording. The discrete rapid deflection in the LRA-V interval preceding the ventricular electrogram by the greatest distance was identified as the HBP. While the HBP was being recorded, there was usually a large atria1 electrogram. This further helped to identify the HBP since the right bundle branch potential was usually accompanied by a small or absent atria1 electrogram. Recording the HRA electrogram was found to be helpful in cases of A-V dissociation and in studying internodal conduction. The HRA-LRA interval is almost always longer and less variable than the P-LRA interval and is thus a more reliable measurement of internodal conduction. The low amplitude of the P-wave makes it subject to errors in measurement. The intervals found in this study in patients January, 1975, Vol. 89, No. 1
Intracardiac
with normal cardiovascular systems and in those with congenital heart defects with normal surface ECG’s agree in general with the intervals reported by other authors. Our findings differ from previous reports in that in our study, statistical analysis of the conduction intervals showed no significant variation with age. Of the previous three studies concerned with the influence of subject age on the intervals, one found a statistically significant increase only in the A-H interva17; the second, an increase only in the H-V6; and the third, an increase with increasing age in both intervals studied.6 Since the premeditations and techniques were similar, it is surprising that such marked differences were found. Our study did not confirm an increase in the P-R interval with increasing age under the conditions of our study. We believe that the phenothiazine drugs used in premeditating children may shorten the P-R interval through effects on autonomic tone and thus make it impossible to determine which interval increases with age. Measurements made under these conditions, however, are useful in determining normal intervals in the cardiac catheterization laboratory setting where any detailed studies muat take place. Our studies of conduction abnormalities indicate that there can be many different sites of block in patients with first-degree A-V block and that these sites can be identified definitely by analysis of IE. Prediction of the site of all forms of atrioventricular block by surface ECG is less accurate in the child with congenital abnormality than in the adult with acquired disease. Bundle branch block was not present in any of our patients with first-degree A-V block and a prolonged H-V interval. This is consistent with Rosen and co-workers,15 who infrequently found a prolonged H-V interval in subjects with right bundle branch block and first-degree A-V block. Whether the various sites of block have the same significance in infants and children as in adults remains to be seen; however, each of the patients with first-degree A-V block and prolonged H-V interval had a defect known to predispose to complete A-V block. It is suspected that patients with first degree A-V block and prolonged H-V interval are prone to develop complete A-V block. Prolongation of the P-LRA and LRA-H intervals in adults has been said to have a more benign prognosis; this study has produced no evidence to contradict this in children. Our findings in the subjects with accelerated American
Heart Journal
electrography
in children
and young adults
A-V conduction agree with studies of adults with this condition in that the QRS morphology is a good predictor of the type of pre-excitation. The conduction intervals in 85 children and young adults with normal conduction by ECG were found to be the same as previously reported for adults, and, contrary to previous reports, did not vary significantly with age. The technique of His bundle recording in children was found to be safe and informative in the study of conduction disturbances and arrhythmias in congenital heart disease, arrhythmias of obscure origin, and localization of the site of heart block. The prognostic value of localizing the site of A-V block in children with IE can be determined only after longer follow-up of these patients. Summary
The interpretation of IE recorded in children has been hampered by a lack of agreement regarding normal values. We recorded IE in 158 children and young adults (ages, three days to 33 years) to define the various conduction intervals in normal and disease states. The HBP was recorded in 156 subjects. In 85 subjects with normal conduction indicated by surface ECG, including 19 subjects with normal hearts, there were no statistically significant age-related differences in internodal, A-V nodal, or His-Purkinje conduction intervals. Therapeutic levels of digitalis did not alter the conduction intervals. In 11 subjects with first degree A-V block and in five subjects with congenital complete A-V block, the site of block as determined by IE could not be predicted from the surface ECG. No abnormalities in conduction intervals were found in 18 subjects with right bundle branch block (surgically induced in 17 cases). Intracardiac electrography with recording of the HBP was found to be a safe, informative technique for electrophysiologic investigations in children and young adults. We would like to acknowledge the technical assistance of Mr. Fidel Elizondo and Mr. Konrad Kail, the editorial assistance of Mrs. Ellen Erwin, and the secretarial assistance of Miss Nan G’Keeffe on this paper. REFERENCES 1.
2.
3.
Damato, A. N., Gallager, J. J., and Lau, S. H.: Application of His bundle recordings in diagnosing conduction disorders, Progr. Cardiovasc. Dis. 14601, 1972. Watson, H., Emslie-Smith, D., and Lowe K. G.: Intracardiac electrocardiogram of human atrioventricular conducting tissue, AM. HEART J. 74:66,1967. Scherlag, B. J., Lau, S. H., Helfant, R. H., Berkowitz, W. 43
Gillette
et al.
D., Stein, E., and Dam&o, A. N.: Catheter techniques for recording His bundle activity in man, Circulation 39:13, 1969.- . 4. Brodsky, S. J., Mirowski, M., Krovetx, L. J., and Rowe R. D.: Recordina of His bundle. and other conduction tissue potentials inchildren, J. Pediatr. 79:61, 1971. 5. Roberts, N. K., and Olley, P. M.: His bundle recordings in children with normal hearts and congenital heart disease, Circulation 46:296, 1972. 6. Abella, J. B., Teixeira, 0. H. P., Misra, K. P., and Hastreiter, A. R.: Changes of atrioventricular conduction with age in infants and children, Am. J. Cardiol. 30~876, 1972. Bekheit, S., Morton, P., Murtagh, J. G., and Fletcher, E.: Comparison of sinoventricular conduction in children and adults using bundle of His electrograms, Br. Heart J. 35:607, 1973. Neches, W. H., Mullins, C. E., Williams, R. L., Vargo, T. A., and MC Namara, D. G.: Percutaneous sheath cardiac catheterization, Am. J. Cardiol. 30~378, 1972. Scherlag, B. J., Samet, P., and Helfant, R. H.: His bundle electrogram: a critical appraisal of its uses and limitations, Circulation 46:601, 1972.
10. Castellanos, A., Jr., Castillo, C. A., and Agha, A. S.: Contribution of His bundle recording to the understanding of clinical arrhythmias, Am. J. Cardiol. 28~499, 1971. 11. Kellv. D. T.. Brodskv. S. J.. Mirowski. M.. Krovetz. L. J.. and “Rowe, R. D.: Bundle of His recordings in congenital complete heart block, Circulation 45:277, 1972. 12. Anderson, P. A. W., Rogers, M. C., Canet, R. V., Jr., Jarmakani, J. M. M., Jewett, P. H., and Spach, M. S.: Reversible complete heart block following cardiac surgery, Circulation 46:614, 1971. 13. Kelly, D. T., Brodsky, S. J., and Krovetx, L. J.: Mobitz Type II atrioventricular block in children, J. Pediatr. 79:972,1971. 14. Gillette, P. C., El-Said, G. L., Sivarajan, N., Mullins, C. E., Williams, R. L., and McNamara, D. G.: Electrophysiologic abnormalities after Mustard operation for transposition of the great arteries, Br. Heart J. 36:186, 1974. 15. Rosen, K. M., Rahimtoola, S. H., Chuquimia, R., Loeb, H. S., and Gunnar, R. M.: Electrophysiological significance of first-degree atrioventricular block with intraventricular conduction disturbance, Circulation 43:491, 1971.
January, 1975, Vd. 89, No. 1
in children
Paul C. Gillette, M.D. Milton J. Reitman, M.D. Howard P. Gutgesell, M.D. Thomas A. Vargo, M.D. Charles E. Mullins, M.D. Dan G. McNamara, M.D. Houston, Texas
Intracardiac electrograms (IE) recorded with electrode catheters are a useful adjunct to surface electrocardiography in the interpretation of conduction disturbances and arrhythmias in adults. Giraud’ was the first to record the His bundle potential (HBP) with catheter electrodes in humans; he recorded unipolar electrograms in children with several forms of congenital heart disease. Watson, Emslie-Smith, and Lowe recorded the HBP in one child with Ebstein’s disease in 1967 using the same technique. This technique was then modified and popularized in 1969 by Scherlag and others3 who recorded bipolar His bundle electrograms @IBE) with band passage set at 40 and 500 Hz. Several recent studies in children have found conflicting variations in the lengths of conduction intervals with age.4-7 The purpose of this study was (1) to determine the normal intervals associated with conduction of the sinus node impulse to the ventricular myocardium in infants and children and changes in these intervals related to age and to compare these values with those measured in normal adults, and (2) to study abnormalities of impulse formation and conduction in children with conduction disturbances and in patients receiving digitalis. From the Section lege of Medicine,
of Cardiology, Department and the Texas Children’s
Supported in part by Grant No. HL6756 of Health, United States Public Health States Public Health Grant RR-00166 Research Branch, National Institutes Received Reprint Texas
36
for publication requests: Children’s
Dr. Paul Hospital,
April
of Pediatrics, Baylor Hospital, Houston.
from the National Service, and in part from the General of Health.
Col-
Institutes by United Clinical
6, 1974.
C. Gillette, Section of Pediatric Cardiology, 6621 Fannin St., Houston, Texas 77026.
Methods Patients. The 158 subjects studied ranged in age from three days to 33 years and in weight from two to 70 kilograms. These cases represent the first 158 consecutive attempts to record the HBP in our institution. All but three subjects, who were studied primarily for evaluation of arrhythmias, underwent diagnostic cardiac catheterization for determination of an anatomic defect and hemodynamic abnormality. “Normal” group. Included among the 158 patients studied were 85 (ages, three days to 29 years) in whom the surface electrocardiogram 1ECG) showed normal conduction. Patients who had intracardiac surgery were excluded from this “normal” group. Twenty-two of the 85 patients were taking digitalis prior to the study; none of these had clinical or electrocardiographic signs of toxicity nor were any of the patients receiving other medications known to alter conduction. Digitalis was withheld for 24 hours prior to the study as part of the preparation for catheterization. The cardiovascular lesions documented by cardiac catheterization in these 85 patients are listed in Table I. Abnormal group. Of the 158 patients, 43 with arrhythmias or conduction disturbances shown by surface ECG were evaluated to determine the effect of these abnormalities on the conduction intervals. The remaining 30 subjects could not be included into either the normal group or any of the specific groups of abnormalities being studied. These subjects are, therefore, included in neither the normal nor the abnormal groups, but are in-
January,
1975, Vol. 89, No. 1, pp. 36-44
Intracardiac
electrography
in children and young adults
Fig. 1. Normal His bundle electrogram MBE) from a lo-month-old child with a normal heart. From top to bottom: Lead II of the surface electrocardiogram; HBE with 1 mm. interelectrode distance: and HBE with 11 mm. interelectrode distance.
eluded in the general statistics such as the success rate. Many of these cases had undergone open-heart surgery. Catheterization techniques. Patients over two months of age were sedated with intramuscular meperidine hydrochloride (1.0 mg. per pound), promethazine hydrochloride (0.25 mg. per pound), and chlorpromazine, (0.25 mg. per pound) one hour before study. The patient and all electrical equipment were securely grounded. The catheter electrodes were connected to an Electronics for Medicine photographic recorder by way of a junction box. Surface ECG’s and IE were recorded simultaneously using frequency band widths of 0.1 to 20 Hz. and 40 to 500 Hz., respectively, at paper speeds of 100 or 200 mm. per second with one-second time lines. Bipolar and tripolar electrode catheters (sizes 4 through 7 French) with interelectrode distances ranging from 1 mm. to 10 mm. were introduced through the femoral or saphenous vein. In children over 10 pounds, the percutaneous sheath technique was used,8 while in smaller infants a saphenous vein cutdown was performed. In a few cases, HBE’s were recorded from the left ventricle with electrode catheters introduced through a sheath previously placed in a femoral artery. When necessary, two electrode catheters were introduced percutaneously either into the same vein or into each of the femoral veins. The electrode catheter was guided with fluoroscopy into the right ventricular apex and
American Heart Journal
Table I. Cardiovascular
normal
conduction
defects in subjects with by surface ECG
Normal structure and hemodynamics Ventricular-septal defect D-transposition of the great arteries Patent ductus arteriosus Pulmonic stenosis Tetralogy of Fallot Aortic stenosis Atrial-septal defect (secunduml Coarctation of the aorta Miscellaneous
19 15 12 I I I 4 4 3 - I
Total
85
then slowly withdrawn with clockwise rotation until the His bundle deflection was seen on the oscilloscope (Fig. 1). Several potentials were recorded sequentially in the low right atrium-toventricle (LRA-V) interval but the potential following the low right atria1 (LRA) deflection which was farthest from the ventricular electrogram was designated the HBP. In some cases, the HBP was recorded from the junction of the left ventricle and left atrium either with the catheter advanced across an atrial-septal defect or patent foramen ovale or by placement of the catheter in a retrograde manner across the aortic valve or into the posterior sinus of Valsalva in the aortic root. To record the high right atria1 (HRA) potential, the catheter
37
Gillette
et al.
Table II. Mean intervals
in subjects with normal
conduction
by surface electrocardiogram Congenital heart disease 66 patients
Interval
Normal hemodynamics (19 patiwlts)
HR PR P-LRA LRA-H H-V Rb-V
107 f 125 f 14 f 73 f 38f 25f
< 2-year-old (21 patients)
25 18 10 17 7 7
136 f 124 f 15 f 72 f 36+ 24f
2-IO-year-old (43 patients)
23 19 12 15 8 8
109 133 18 75 41 26
f f f f f f
> 1 O-year-old (14 patients)
20 19 16 19 10 10
91 130 13 79 42 28
f f f f f f
20 10 12 17 11 11
All intervals are the mean value in milliseconds f ISEM. HR, heart rate. P, beginning of P-wave in surface ECG. LRA, low right atrium. H, His bundle. Rb, right bundle branch. V, ventricle.
Table Ill. Conduction
abnormalities mias studied in 43 subjects First-degree A-V block Second-degree A-V block Third-degree A-V block RBBB Short PR Premature beats
and arrhyth11 2 5 18 6 4 46
was positioned at the junction of the superior vena cava and right atrium. Conduction intervals. The intervals measured and their anatomic correlates are defined below: P-LRA. Beginning of P-wave on simultaneously recorded surface ECG to first atria1 deflection on the HBE. This estimates the conduction time from the sinoatrial node to atrioventricular (A-V) node. HRA-LRA. First rapid deflection on the HRA electrogram to first rapid deflection of the LRA electrogram. This allows a more precise estimate of conduction from the area of the sinoatrial node to the area of the A-V node than does the P-LRA interval. LRA-H. First rapid deflection of LRA electrogram to first rapid deflection of HBP. This represents conduction time through the A-V node. H-V. First rapid deflection of HBP to the earliest ventricular activity either on surface ECG or IE. This represents conduction time from the His bundle to the ventricular myocardium. R&V. First rapid deflection of a potential after the HBP to the earliest ventricular activity. This
38
represents conduction time from the right dle to the ventricular myocardium.
bun-
Results
The His bundle potential was identified in 156 out of 158 patients in whom this technique was attempted. HBP’s were recorded in virtually all congenital heart lesions including complex lesions such as transposition of the great arteries before and after surgical correction, ventricular inverserion, tetralogy of Fallot, endocardial cushion defects, and tricuspid atresia, as well as simpler lesions. The right bundle branch potential and the right bundle-to-ventricle interval were also measured in 45 patients. There were no complications. “Normal” group. Table II lists the values for several conduction intervals determined from the IE in 85 subjects with normal conduction on the surface ECG. Diagnostic catheterization confirmed the presence of a congenital cardiac defect in 66 of these subjects and proved the heart to be structurally normal in the remaining 19 subjects. Statistical analysis of the conduction intervals by Student’s t-test showed no statistically significant difference between intervals measured in subjects with structurally normal hearts and in those subjects with congenital heart disease. No statistical differences were found among the three age groups, nor between the patients who had received digitalis and those who had not. Abnormal group. The types of conduction abnormalities or arrhythmias found in the 43 subjects with abnormal surface ECG are listed in Table III. First-degree A-V block. The conduction inter-
January,
1975, Vol. 89, No. 1
Intracardiac Table IV. Intervals
in subjects with first-degree
electrography in children and young adults
atrioventricular
block QRS
PR
HR Age fjTS.)
duration
P-LRA
p/o VSD T/F Complex ASDI p/o ASD-VSD p/o ASD I VI, DILV ASDI p/o ASD I T/F p/o common
msec. 175 210 160 200 200 197 250 200 175 200 225
107 100 125 100 85 72 80 109 110 133 100
ventricle
p/o, postoperative. VSD, ventricular-septal double-inlet left ventricle.
Table V. Intervals
H-V IIlrIz
DiilglUWiS
22112 2 18112 2 8 10 21 7 12 4 5
LRA-H
defect. T/F, tetralogy
120 90 95 125 120 120 100 115 110 96 125
of Fallot. ASD I, ostiurn primurn
in subjects with pre-excitation
0 0 35 0 5 7 0 30 30 30 25 etrial-septal
Table VI. Intervals
135 180 105 155 140 135 150 135 70 100 170
40 30 20 45 55 55 100 40 75 70 30
defect. VI, ventricular
inversion.
DILV,
in subjects with right bundle
branch block QRS
HR
Associated diugnosis
8 m. f5yr. 2 mo. 20 mo.
2 yr. 20 mo. AS, aortic defect.
Normal hemodynamics AS, PS Left atrial rhahdomyoma Pompa’s disease Normal hemodynamics VSD stenosis.
PS. pulmonic
PR LRA-H
H-V HR
msec. 120
83
110
95
15
110 70
80 80
105 80
100 50
0 30
80 90
129 160
90 75
35 30
30 35
80
100
100
55
35
stenosis.
VSD, ventricular-septal
vals measured in 11 subjects with first-degree A-V block, none of whom were taking cardioactive drugs, are shown in Table IV. A prolonged LRA-H interval was demonstrated in eight of the 11 subjects, a prolonged H-V interval in two subjects, and prolongation of both intervals in one subject. Third-degree A-V block Congenital complete A-V block was present in five of the 43 subjects with arrhythmias. Three of these five subjects also had ventricular inversion; in these cases, the block was found below the bundle of His potential. In the fourth subject, the block was above the bundle of His. In the fifth subject, the site of block was in the bundle of His indicated by the occurrence of two separate His potentials (“split His”), one following atria1 deflection, and the
American Heart Journal
Age (yr.) 12 3 4 22112 8 17 18 4 8 33 11 4 3 12 14 6 4% 5
PR
Diagrwsis p/o T/F PPH p/o T/F p/o VSD p/o ASD-VSD p/o truncus p/o VSD p/o T/F p/o truncua p/o T/F p/o TIP p/o T/F p/o DORV (dextrocardia) p/o T/F p/o VSD p/o T/F p/o T/F p/o common ventricle
LRA-H
H-V
Rb-V
10 -
malee. 83 58 95 107 85 90 85 100 95 86 80 90 105
170 140 120 175 200 180 150 170 150 130 105 140 115
115 100 90 135 140 85 80 110 125 85 60 100 75
55 40 30 40 55 45 45 60 55 45 50 45 35
120 140 83 170 85 125 110 150 100 225
60 90 75 80 170
45 45 43 48 30
10 30 25 25 35 30 10
p/o, postoperative. T/F, tetralogy of Fallot. PPH. primary pulmonary hypertension. VSD, ventricular-septal defect. ASD. atrial-septal defect. DORV, double-outlet right ventricle.
other preceding
ventricular
depolarization
(Fig.
2). Short P-R interval. Six subjects with short P-R
intervals were studied (Table V). Shortening of the H-V interval was found in two subjects with QRS prolongation (Wolff-Parkinson-White syn-
39
Gillette
et al.
Fig. 2. His bundle electrogram from a child with congenital complete heart block demonstrating a “split His” potential; that is, His potentials following each low right atrial potential and before each ventricular electrogram indicative of block in the common bundle of His.
Fig. 3. His bundle electrogram of tachycardia demonstrating bypass.
in a 20-month-old child with a VSD, short PR interval, normal QRS, and a history shortened atrial to His bundle conduction consistent with atrioventricular node
drome) and shortening of the LRA-H interval was found in the four subjects with normal QRS duration and morphology (Fig. 3). Right bundle branch block. The surface ECG indicated the presence of right bundle branch block pattern in 18 subjects; none had associated left anterior hemiblock. In 17 subjects, the bundle branch block pattern had resulted from cardiac surgery. The H-V interval in all 18 cases was within two standard deviations of the normal mean. The right bundle branch electrogram was identifiable in only seven cases; the Rb-V interval was normal in each of these cases (Fig. 4). Premature complexes or paroxysmal tachycardia. IE were recorded in four subjects to inves-
40
tigate multiple premature complexes or paroxysmal tachycardia of obscure origin. In one case, both atria1 and His bundle potentials were found before each premature complex indicating an atria1 origin. In another case, only His potentials were identified and the H-V intervals were 10 msec. shorter than conducted beats, indicating origin of the premature beats to be in a bundle branch. In the third case, no atria1 or His potentials were recorded before the premature beats, whereas they were recorded during comparable time before conducted beats, showing the premature beats arose in the ventricular myocardium. The fourth child had normal intervals both at rest and with multiple premature atria1 con-
January, 1975, Vol. 89, No. 1
Intracardiac
,_,
‘id
*
electrography
in children and young adults
i
’
Fii. A His bundle and right bundle branch potentials recorded in a three-year-old after correction of double outlet right ventricle with dextrocardia at which time a right bundle branch block pattern was induced on her electrocardiogram.
Fig. 5. His bundle electrograms from a six-month-old patient with recurrent intervals during sinus rhythm but no His potential during tachycardia.
American Heart Journal
tachycardia demonstrating
normal
41
Gillette
et al.
Fig. 6, His bundle electrogram from a la-year-old girl six years after surgical correction cushion defect demonstrating a prolonged H-V interval of 70 milliseconds.
tractions, but during a paroxysm of tachycardia, no His potential could be found, indicating along with the A-V disassociation and wide QRS complexes, either ventricular tachycardia or nodal tachycardia with extra-Hisian pre-excitation (Fig. 5). The findings in the other 30 subjects were varied. Twelve of the subjects had undergone Mustard operation and their conduction intervals were normall Nine patients had ostium primum atrial-septal defect and, with the exception of those who had undergone surgery, the conduction intervals were also normal. Studies were performed in two other subjects to delineate the type of A-V block present following cardiac surgery. One eight-year-old boy who had transient complete A-V block after surgery to remove a subvalvular pulmonic stenosis associated with ventricular inversion had normal intervals 10 days after surgery. The other subject with transient complete A-V block postoperatively was studied six years after surgery because of syncopal attacks. Despite a sinus rhythm, this patient had a prolonged H-V interval (Fig. 61. Discussion
Intracardiac electrography is useful in interpreting and treating certain obscure arrhythmias and conduction disturbances in adults,lT g especially in determining the site and type of A-V block, the localization of the focus for tachyarrhythmias, and the type of accelerated A-V conduction.1° Studies in children have been concerned with congenital heart block,” surgical heart block,12, Mobitz Type II block,13 and electrophysiologic abnormalities after Mustard operation.14 There are several reports of normal con42
of an endocardial
duction intervals for adults and three reports of conduction intervals in children with congenital heart disease with and without abnormal surface ECG’S.~-~ The effect of digitalis on conduction has not been studied in children. It is necessary to differentiate the right bundle branch potential from the HBP since confusing the HBP with the right bundle branch potential would give a falsely small value for the H-V interval. Other investigators have accomplished this either by His bundle pacing or by evaluating the response of the conduction intervals to right atria1 pacing. Neither of these methods are completely reliable and both introduce possible additional hazards to the patient, i.e., high milliamperage needed for His bundle pacing and additional catheter for atria1 pacing. We, therefore, used a different method to identify the His bundle potential. We withdrew the catheter slowly across the tricuspid valve while recording. The discrete rapid deflection in the LRA-V interval preceding the ventricular electrogram by the greatest distance was identified as the HBP. While the HBP was being recorded, there was usually a large atria1 electrogram. This further helped to identify the HBP since the right bundle branch potential was usually accompanied by a small or absent atria1 electrogram. Recording the HRA electrogram was found to be helpful in cases of A-V dissociation and in studying internodal conduction. The HRA-LRA interval is almost always longer and less variable than the P-LRA interval and is thus a more reliable measurement of internodal conduction. The low amplitude of the P-wave makes it subject to errors in measurement. The intervals found in this study in patients January, 1975, Vol. 89, No. 1
Intracardiac
with normal cardiovascular systems and in those with congenital heart defects with normal surface ECG’s agree in general with the intervals reported by other authors. Our findings differ from previous reports in that in our study, statistical analysis of the conduction intervals showed no significant variation with age. Of the previous three studies concerned with the influence of subject age on the intervals, one found a statistically significant increase only in the A-H interva17; the second, an increase only in the H-V6; and the third, an increase with increasing age in both intervals studied.6 Since the premeditations and techniques were similar, it is surprising that such marked differences were found. Our study did not confirm an increase in the P-R interval with increasing age under the conditions of our study. We believe that the phenothiazine drugs used in premeditating children may shorten the P-R interval through effects on autonomic tone and thus make it impossible to determine which interval increases with age. Measurements made under these conditions, however, are useful in determining normal intervals in the cardiac catheterization laboratory setting where any detailed studies muat take place. Our studies of conduction abnormalities indicate that there can be many different sites of block in patients with first-degree A-V block and that these sites can be identified definitely by analysis of IE. Prediction of the site of all forms of atrioventricular block by surface ECG is less accurate in the child with congenital abnormality than in the adult with acquired disease. Bundle branch block was not present in any of our patients with first-degree A-V block and a prolonged H-V interval. This is consistent with Rosen and co-workers,15 who infrequently found a prolonged H-V interval in subjects with right bundle branch block and first-degree A-V block. Whether the various sites of block have the same significance in infants and children as in adults remains to be seen; however, each of the patients with first-degree A-V block and prolonged H-V interval had a defect known to predispose to complete A-V block. It is suspected that patients with first degree A-V block and prolonged H-V interval are prone to develop complete A-V block. Prolongation of the P-LRA and LRA-H intervals in adults has been said to have a more benign prognosis; this study has produced no evidence to contradict this in children. Our findings in the subjects with accelerated American
Heart Journal
electrography
in children
and young adults
A-V conduction agree with studies of adults with this condition in that the QRS morphology is a good predictor of the type of pre-excitation. The conduction intervals in 85 children and young adults with normal conduction by ECG were found to be the same as previously reported for adults, and, contrary to previous reports, did not vary significantly with age. The technique of His bundle recording in children was found to be safe and informative in the study of conduction disturbances and arrhythmias in congenital heart disease, arrhythmias of obscure origin, and localization of the site of heart block. The prognostic value of localizing the site of A-V block in children with IE can be determined only after longer follow-up of these patients. Summary
The interpretation of IE recorded in children has been hampered by a lack of agreement regarding normal values. We recorded IE in 158 children and young adults (ages, three days to 33 years) to define the various conduction intervals in normal and disease states. The HBP was recorded in 156 subjects. In 85 subjects with normal conduction indicated by surface ECG, including 19 subjects with normal hearts, there were no statistically significant age-related differences in internodal, A-V nodal, or His-Purkinje conduction intervals. Therapeutic levels of digitalis did not alter the conduction intervals. In 11 subjects with first degree A-V block and in five subjects with congenital complete A-V block, the site of block as determined by IE could not be predicted from the surface ECG. No abnormalities in conduction intervals were found in 18 subjects with right bundle branch block (surgically induced in 17 cases). Intracardiac electrography with recording of the HBP was found to be a safe, informative technique for electrophysiologic investigations in children and young adults. We would like to acknowledge the technical assistance of Mr. Fidel Elizondo and Mr. Konrad Kail, the editorial assistance of Mrs. Ellen Erwin, and the secretarial assistance of Miss Nan G’Keeffe on this paper. REFERENCES 1.
2.
3.
Damato, A. N., Gallager, J. J., and Lau, S. H.: Application of His bundle recordings in diagnosing conduction disorders, Progr. Cardiovasc. Dis. 14601, 1972. Watson, H., Emslie-Smith, D., and Lowe K. G.: Intracardiac electrocardiogram of human atrioventricular conducting tissue, AM. HEART J. 74:66,1967. Scherlag, B. J., Lau, S. H., Helfant, R. H., Berkowitz, W. 43
Gillette
et al.
D., Stein, E., and Dam&o, A. N.: Catheter techniques for recording His bundle activity in man, Circulation 39:13, 1969.- . 4. Brodsky, S. J., Mirowski, M., Krovetx, L. J., and Rowe R. D.: Recordina of His bundle. and other conduction tissue potentials inchildren, J. Pediatr. 79:61, 1971. 5. Roberts, N. K., and Olley, P. M.: His bundle recordings in children with normal hearts and congenital heart disease, Circulation 46:296, 1972. 6. Abella, J. B., Teixeira, 0. H. P., Misra, K. P., and Hastreiter, A. R.: Changes of atrioventricular conduction with age in infants and children, Am. J. Cardiol. 30~876, 1972. Bekheit, S., Morton, P., Murtagh, J. G., and Fletcher, E.: Comparison of sinoventricular conduction in children and adults using bundle of His electrograms, Br. Heart J. 35:607, 1973. Neches, W. H., Mullins, C. E., Williams, R. L., Vargo, T. A., and MC Namara, D. G.: Percutaneous sheath cardiac catheterization, Am. J. Cardiol. 30~378, 1972. Scherlag, B. J., Samet, P., and Helfant, R. H.: His bundle electrogram: a critical appraisal of its uses and limitations, Circulation 46:601, 1972.
10. Castellanos, A., Jr., Castillo, C. A., and Agha, A. S.: Contribution of His bundle recording to the understanding of clinical arrhythmias, Am. J. Cardiol. 28~499, 1971. 11. Kellv. D. T.. Brodskv. S. J.. Mirowski. M.. Krovetz. L. J.. and “Rowe, R. D.: Bundle of His recordings in congenital complete heart block, Circulation 45:277, 1972. 12. Anderson, P. A. W., Rogers, M. C., Canet, R. V., Jr., Jarmakani, J. M. M., Jewett, P. H., and Spach, M. S.: Reversible complete heart block following cardiac surgery, Circulation 46:614, 1971. 13. Kelly, D. T., Brodsky, S. J., and Krovetx, L. J.: Mobitz Type II atrioventricular block in children, J. Pediatr. 79:972,1971. 14. Gillette, P. C., El-Said, G. L., Sivarajan, N., Mullins, C. E., Williams, R. L., and McNamara, D. G.: Electrophysiologic abnormalities after Mustard operation for transposition of the great arteries, Br. Heart J. 36:186, 1974. 15. Rosen, K. M., Rahimtoola, S. H., Chuquimia, R., Loeb, H. S., and Gunnar, R. M.: Electrophysiological significance of first-degree atrioventricular block with intraventricular conduction disturbance, Circulation 43:491, 1971.
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