His Bundle Electrogram After Intracardiac Repair of Tetralogy of Fallot Analysis of Data in 59 Patients
THOMAS J. HOUGEN, M.D.’ MACDONALD DICK, II, MDt MICHAEL D. FREED, MD JOHN F. KEANE, MD 6OStOt7, ibii7SSaChUS8ttS
From the Department of Cardiology, Children’s Hospital Medical Center, and the Department of Pediatrics, Harvard Medical School, Boston, Massachusetts. This work was supported in part by Grants HL 10436 and HL 05655 from the National Instiies of Health, Bethesda, Maryland, and the King Trust Fund. Manuscript received May 2, 1977; revised manuscript received September 15, 1977, accepted October 22,1977. Charles A. Janeway Scholar. Present address: Deparbnent of Pediatrics, San Diego Naval Hospital, San Diego, California. + Present address: Macdonald Dick, II. MD, Section of Pediatric Cardiology, CS f&tt Children’s Hospital, University of Michigan, Ann Arbor, Michigan. Address for reprints: John F. Keane, MD, Department of Cardiology, Children’s Hospital Medical Center, 300 Longwood Avenue, Boston, Massachusetts 02 115. l
552
March 1979
HIS bundle electrograms were recorded in 59 patients after intracardiac repair of tetralogy of Fallot and were correlated with the postoperative electrocardiogram. Except for five patients with first degree atrioventricular block postoperatively all patients in Group A (those with either a normal electrocardiogram or solitary right bundle branch block) had a normal A-H interval (77.7 f 21.6 msec):(mean f standard deviation); all had a normal H-V interval (39.5 f 7.2 msec). Patients in Group 6 (bifascicular block) tended to have a normal A-H tnterval(97.2 f 26.2 msec) with a prolonged H-V interval (48.8 f 10.7 msec). Patients in Group C (trifascicular blook) had prolongation of both the A-H (160.0 f 32.4 msec) and the H-V interval (58.8 f 10.6 msec) by comparison with control values. Patients in Group D (transient complete heart block) had a normal A-H interval (79.5 f 28.2 msec) but a prolonged H-V interval (57.8 f 16.4 msec), similar to that In Group C. A good hemodynamic result was associated with a normal H-V interval; a prolonged interval accompanied a poor result.
Abnormalities in atrioventricular (A-V) conduction are known to occur after intracardiac repair of tetralogy of Fallot. Postoperatively, the majority of patients have a right bundle branch block pattern in the surface electrocardiogram l; 8 to 22 percent manifest bifascicular block2-l2 and 4 percent the electrocardiographic pattern of trifascicular block.12 Within recent years only a small group, 1 to 2 percent, have shown complete heart block. 13,14The reported consequences of these A-V conduction abnormalities vary. In one series,4 the mortality related to cardiac arrhythmias was 25 percent (6 of 24) in patients with bifascicular block after surgery; in other series the investigators1’J2 were unable to relate bifascicular block and poor outcome although in one report12 trifascicular block resulted in a 30 percent incidence rate of sudden death (3 of 10). In yet another group2 sudden death occurred in 3 percent (4 of 181) of patients without bifascicular block but with exercise-induced ventricular ectopy. Complete heart block is usually associated with a poor outcome,13 may develop a number of years after operation14 and usually requires a permanent pacemaker.14 Thus, A-V conduction abnormalities appear to affect prognosis after repair of tetralogy of Fallot. To determine the extent of surgically induced A-V conduction abnormalities and their relation to the surface electrocardiogram, hemodynamic results and outcome, we obtained His bundle electrograms from 59 patients after repair of tetralogy of Fallot. Material
and Methods
Patients: Sixty postoperative patients with tetralogy of Fallot were evaluated at routine follow-up cardiac catheterization. One patient was excluded from the study because of severe subaortic stenosis. The remaining 59 patients evaluated between April 1,1974 and June 30,1976 represent a consecutive series of patients who had a technically satisfactory His bundle electrogram after repair of
The American Journal of CARDfOLOGY
Volume 41
H-V INTERVAL AFTER REPAIR OF TETRALOGY OF FALLOT-HOUGEN ET AL.
tetralogy of Fallot. Thirty-three of the patients were studied within 2 years of operation. Fourteen preoperative patients, 12 with tetralogy of Fallot (median age 7 11/12 years), served as control subjects. Electrocardiograms: The pre- and postoperative electrocardiograms of all 59 postoperative patients were examined. No patient had right bundle branch block preoperatively (rSR’ in lead VI, a deep slurred S wave in leads I and Vs and QRS duration of 0.12 second or more).1°J5 All patients had right ventricular hypertrophy and 56 had right axis deviation before operation. Three patients in Group A but none in Groups B, C or D had a leftward superior frontal plane electrocardiographic axis preoperatively. After operation six patients did not meet the criteria for right. bundle branch block (including rate-related prolongation of the QRS interval); in four of these six there was no change in QRS configuration or duration, and in two the QRS interval lengthened by 0.03 second but not sufficiently to permit the diagnosis of right bundle branch block. Classification of postoperative electrocardiograms: The 59 patients were then classified according to postoperative electrocardiographic findings. Group A comprised 44 patients with either normal intraventricular conduction or right bundle branch block. Group B consisted of five patients with bifascicular block (right bundle branch block and left anterior hemiblock [superior frontal plane axis of -30” or less, with a counterclockwise 10op]).~~ The five patients in Group C manifested the electrocardiographic pattern of trifascicular block postoperatively (bifascicular block and first degree A-V block). One of the five (Case 2) also had transient complete heart block. Group D was composed of four patients with transient complete heart block (recorded in the intensive care unit and persisting for not. more than 3 weeks postoperatively). An additional patient (Case 15) had transient bifascicular block postoperatively lasting 10 days,16 but at follow-up study manifested right bundle branch block, first degree A-V block and a clockwise frontal plane loop in the vectorcardiogram. The postoperative electrocardiographic changes in all four groups were observed shortly after operation in the intensive care unit (maximal interval 6 months in Patient 14) and did not change thereafter except in Patient 15 and in all patients in Group D, who had reversion to intact A-V conduction. Cardiac catheterization studies and His bundle recordings: These were performed with patients in the postabsorptive state under light sedation with an intramuscular injection of meperidine (2 mg/kg, not exceeding 50 mg), promethazine hydrochloride (0.25 mg/kg, not exceeding 12.5 mg) and chlorpromazine (0.25 mg/kg, not exceeding 12.5 mg). Digoxin, taken by 15 patients, was omitted on the morning of catheterization. Intracardiac electrode catheters were connected to a Hewlett-Packard bioelectric high input impedance differential amplifier (MN 8811A). His bundle electrograms were recorded through either bipolar or unipolar electrodes at a band width of 15 to 300 hertz with use of an optical writer on photographic paper moving at either 100 or 200 mm/ sec.*7J8 A simultaneous lead II electrocardiogram was also recorded. Appropriate intervals were measured in three or four beats and a mean value was derived. The A-H interval was measured from the onset of the A wave to the onset of the H deflection. The H-V interval was taken from the onset of the H deflection to the onset of either the V wave of the ventricular electrogram or the Q wave of the lead II electrocardiogram, whichever came first.lg The hemodynamic findings at cardiac catheterization were graded according to criteria modified from Ruzyllo et al.20 A good repair was defined as follows: (1) no ventricular septal
defect; (2) a peak systolic ejection gradient across the right ventricular outflow tract of 40 mm Hg or less or a peak right
ventricular systolic pressure of 50 percent or less of systemic pressure,2 or both. A fair repair was defined as (1) a residual ventricular septal defect with a pulmonary to systemic flow ratio of 1.5:1 or less; (2) a peak systolic ejection gradient across the right ventricular outflow tract of 60 mm Hg or less or a peak right ventricular systolic pressure of 75 percent or less of systemic pressure, or both. A repair was considered poor if there were (1) a residual ventricular septal defect with a pulmonary to systemic flow ratio greater than 1.5:1, and (2) a peak systolic ejection gradient across the right ventricular outflow tract greater than 60 mm Hg or a peak right ventricular systolic pressure greater than 75 percent of systemic pressure, or both. These three hemodynamic categories were correlated with the electrocardiographic groups. Statistical analyses were carried out using Student’s t test for grouped data.
Results His bundle electrograms (Tables I and II, Fig. 1): The 14 control patients had a mean A-H interval of 84.4 f 28 msec (k standard deviation) and an H-V interval of 35.8 f 7.1 msec. These intervals are similar to normal values for age (Fig. 1).21-24 Patients in Group A generally had normal His bundle electrographic intervals; after correction for age and heart rate, the A-H interval was prolonged in five patients with first degree A-V block; in the remainder, it was normal (77.7 f 21.6 msec). In all 44 patients in Group A the H-V interval was normal (39.5 f 7.2 msec). Patients in both Groups B and D had an A-H interval not significantly different from that of the control group (97.2 f 26.2 and 79.5 f 28.2 msec, respectively). Patients in Group C had a prolonged A-H interval (160.0 f 32.4 msec) that was nearly twice the value recorded in the control group and the other three groups. The H-V interval was significantly prolonged, by comparison with control values, in Groups B (48.8 f 10.7 msec), C (58.8 f 10.6 msec) and D (57.8 f 16.4 msec). One patient (Case 2) had both bifascicular block and transient complete A-V block but was included only in group B; he was 7 9/12 years old when he underwent correction of tetralogy of Fallot. In the operating room, transient complete A-V block appeared for several minutes. The His bundle recording 1 l/2 years later disclosed normal A-V conduction times of the A-H (65 msec) and H-V (46 msec) intervals. A second patient (Case 8) underwent initial repair at age 112/12 years. For several minutes while still in the operating room, he had transient complete heart block. After A-V conduction resumed in the intensive care unit, trifascicular block was noted in the surface electrocardiogram. At recatheterization 9 11/12 years later the His bundle electrogram disclosed a prolonged H-V interval (71 msec). He died at reoperation for a large residual ventricular septal defect and pulmonary stenosis at age 212112 years. Patient 14 had transient complete heart block for 3 weeks after operation (age 11 lo/12 years). At age 20 a His bundle study disclosed 2:l H-V block (infraHis) at an atria1 pacing rate of 125/min. Administration of atropine shortened A-H conduction slightly but did not alter the response of the H-V interval to atria1 pacing. In Patient 9 an initial operation at age 9 9/12 years yielded a poor hemodynamic result and the electrocardiographic pattern of trifascicular block. Reoperation 2 years later for a residual ventricular septal defect and pulmonary stenosis resulted in a good hemodynamic repair and a normal H-V interval at rest. With atria1 pacing at a rate of llO/min, 2:l A-H A-V block
March 1978
The Amorlcan Journal of CARDIOLOGY
Volume 41
553
H-V INTERVAL AFTER REPAIR OF TETRALOGY OF FALLOT-HOUGEN ET AL.
TABLE I Summary of Data in Groups B, C and D Postoperative Electrocardiogram CtRS AXIS P-R Interval Frontal QRS VI (seconds) Pattern Plane
Case no.
Hemodynamic Result
Intervals A-H H-V (msec) (msec)
Outcome
Right Atrial Pacino
...
Group 6 (bifascicular block) 0.14 0.18 0.16
RBBB RBBB
-90 -60 -45
Good Poor Fair
118 t
0.14 0.18
RBBB
-150 -120
Good Poor
129 82
S’
Grout C ftrifascicular block) 7
0.22
RBBB
-100
Poor
166 153
55 87
Alive Dead
: 10
0.22 0.26 0.26
RBBB RBBB
-90 -45
P-G Poor Poor
150 121 210
44 71 57
Dead Alive Alive
5:
Alive
60 77
Alive
142
Alive
Supra-&
block
...
Group 0 (transient complete heart block) :: ::
0.18 0.14 0.16 0.18
RBBB RBBB RBBB
Poor Good Good
+120 +90 +135 +90
Good
Ei 1:;
... Infra&‘block
Other’ 15
0.18
RBBB
+210
Poor
89
This patient had transient bifascicular block postoperatively for 10 days but at follow-up study manifested right bundle branch block, first degree A-V block and a clockwise frontal plane loop in the vectorcardiogram. P --+ G = poor after initial repair; good after reoperation. l
(supra-His or within the A-V node) developed while the H-V interval remained constant. A fifth patient (Case 15) had transient bifascicular block for 10 days after an initial repair at age 7 4/12 years. Follow-up catheterization 11 months later revealed a large ventricular septal defect and pulmonary stenosis. The His bundle electrogram demonstrated an A-H interval of 86 msec and a markedly prolonged H-V interval of 142 msec (Fig. 2). Neither the scalar electrocardiogram nor the vectorcardiogram revealed bifascicular block. Reoperation was successful.
His bundle electrogram versus surface electrocardiogram: In this series, 60 percent (9 of 15) of the
TABLE ii His Bundle Eiectrographic intervals Related to Electrocardiographic Group Intervals (mean f SD) H-V (msec) A-H (msec)
Group
CAontro :t B :
5 :
Other
1
84.4 77.7 f 28.0 21.6+ 97.2 f 26.2 160.0 79.5 f 28.2 32.4 78
39.5 f 7.1 35.8 7.2 48.8 f 57.8 58.8 f 142
10.7 10.6 16.4
Pvalue’ H-V
..
THOMAS J. HOUGEN, M.D.’ MACDONALD DICK, II, MDt MICHAEL D. FREED, MD JOHN F. KEANE, MD 6OStOt7, ibii7SSaChUS8ttS
From the Department of Cardiology, Children’s Hospital Medical Center, and the Department of Pediatrics, Harvard Medical School, Boston, Massachusetts. This work was supported in part by Grants HL 10436 and HL 05655 from the National Instiies of Health, Bethesda, Maryland, and the King Trust Fund. Manuscript received May 2, 1977; revised manuscript received September 15, 1977, accepted October 22,1977. Charles A. Janeway Scholar. Present address: Deparbnent of Pediatrics, San Diego Naval Hospital, San Diego, California. + Present address: Macdonald Dick, II. MD, Section of Pediatric Cardiology, CS f&tt Children’s Hospital, University of Michigan, Ann Arbor, Michigan. Address for reprints: John F. Keane, MD, Department of Cardiology, Children’s Hospital Medical Center, 300 Longwood Avenue, Boston, Massachusetts 02 115. l
552
March 1979
HIS bundle electrograms were recorded in 59 patients after intracardiac repair of tetralogy of Fallot and were correlated with the postoperative electrocardiogram. Except for five patients with first degree atrioventricular block postoperatively all patients in Group A (those with either a normal electrocardiogram or solitary right bundle branch block) had a normal A-H interval (77.7 f 21.6 msec):(mean f standard deviation); all had a normal H-V interval (39.5 f 7.2 msec). Patients in Group 6 (bifascicular block) tended to have a normal A-H tnterval(97.2 f 26.2 msec) with a prolonged H-V interval (48.8 f 10.7 msec). Patients in Group C (trifascicular blook) had prolongation of both the A-H (160.0 f 32.4 msec) and the H-V interval (58.8 f 10.6 msec) by comparison with control values. Patients in Group D (transient complete heart block) had a normal A-H interval (79.5 f 28.2 msec) but a prolonged H-V interval (57.8 f 16.4 msec), similar to that In Group C. A good hemodynamic result was associated with a normal H-V interval; a prolonged interval accompanied a poor result.
Abnormalities in atrioventricular (A-V) conduction are known to occur after intracardiac repair of tetralogy of Fallot. Postoperatively, the majority of patients have a right bundle branch block pattern in the surface electrocardiogram l; 8 to 22 percent manifest bifascicular block2-l2 and 4 percent the electrocardiographic pattern of trifascicular block.12 Within recent years only a small group, 1 to 2 percent, have shown complete heart block. 13,14The reported consequences of these A-V conduction abnormalities vary. In one series,4 the mortality related to cardiac arrhythmias was 25 percent (6 of 24) in patients with bifascicular block after surgery; in other series the investigators1’J2 were unable to relate bifascicular block and poor outcome although in one report12 trifascicular block resulted in a 30 percent incidence rate of sudden death (3 of 10). In yet another group2 sudden death occurred in 3 percent (4 of 181) of patients without bifascicular block but with exercise-induced ventricular ectopy. Complete heart block is usually associated with a poor outcome,13 may develop a number of years after operation14 and usually requires a permanent pacemaker.14 Thus, A-V conduction abnormalities appear to affect prognosis after repair of tetralogy of Fallot. To determine the extent of surgically induced A-V conduction abnormalities and their relation to the surface electrocardiogram, hemodynamic results and outcome, we obtained His bundle electrograms from 59 patients after repair of tetralogy of Fallot. Material
and Methods
Patients: Sixty postoperative patients with tetralogy of Fallot were evaluated at routine follow-up cardiac catheterization. One patient was excluded from the study because of severe subaortic stenosis. The remaining 59 patients evaluated between April 1,1974 and June 30,1976 represent a consecutive series of patients who had a technically satisfactory His bundle electrogram after repair of
The American Journal of CARDfOLOGY
Volume 41
H-V INTERVAL AFTER REPAIR OF TETRALOGY OF FALLOT-HOUGEN ET AL.
tetralogy of Fallot. Thirty-three of the patients were studied within 2 years of operation. Fourteen preoperative patients, 12 with tetralogy of Fallot (median age 7 11/12 years), served as control subjects. Electrocardiograms: The pre- and postoperative electrocardiograms of all 59 postoperative patients were examined. No patient had right bundle branch block preoperatively (rSR’ in lead VI, a deep slurred S wave in leads I and Vs and QRS duration of 0.12 second or more).1°J5 All patients had right ventricular hypertrophy and 56 had right axis deviation before operation. Three patients in Group A but none in Groups B, C or D had a leftward superior frontal plane electrocardiographic axis preoperatively. After operation six patients did not meet the criteria for right. bundle branch block (including rate-related prolongation of the QRS interval); in four of these six there was no change in QRS configuration or duration, and in two the QRS interval lengthened by 0.03 second but not sufficiently to permit the diagnosis of right bundle branch block. Classification of postoperative electrocardiograms: The 59 patients were then classified according to postoperative electrocardiographic findings. Group A comprised 44 patients with either normal intraventricular conduction or right bundle branch block. Group B consisted of five patients with bifascicular block (right bundle branch block and left anterior hemiblock [superior frontal plane axis of -30” or less, with a counterclockwise 10op]).~~ The five patients in Group C manifested the electrocardiographic pattern of trifascicular block postoperatively (bifascicular block and first degree A-V block). One of the five (Case 2) also had transient complete heart block. Group D was composed of four patients with transient complete heart block (recorded in the intensive care unit and persisting for not. more than 3 weeks postoperatively). An additional patient (Case 15) had transient bifascicular block postoperatively lasting 10 days,16 but at follow-up study manifested right bundle branch block, first degree A-V block and a clockwise frontal plane loop in the vectorcardiogram. The postoperative electrocardiographic changes in all four groups were observed shortly after operation in the intensive care unit (maximal interval 6 months in Patient 14) and did not change thereafter except in Patient 15 and in all patients in Group D, who had reversion to intact A-V conduction. Cardiac catheterization studies and His bundle recordings: These were performed with patients in the postabsorptive state under light sedation with an intramuscular injection of meperidine (2 mg/kg, not exceeding 50 mg), promethazine hydrochloride (0.25 mg/kg, not exceeding 12.5 mg) and chlorpromazine (0.25 mg/kg, not exceeding 12.5 mg). Digoxin, taken by 15 patients, was omitted on the morning of catheterization. Intracardiac electrode catheters were connected to a Hewlett-Packard bioelectric high input impedance differential amplifier (MN 8811A). His bundle electrograms were recorded through either bipolar or unipolar electrodes at a band width of 15 to 300 hertz with use of an optical writer on photographic paper moving at either 100 or 200 mm/ sec.*7J8 A simultaneous lead II electrocardiogram was also recorded. Appropriate intervals were measured in three or four beats and a mean value was derived. The A-H interval was measured from the onset of the A wave to the onset of the H deflection. The H-V interval was taken from the onset of the H deflection to the onset of either the V wave of the ventricular electrogram or the Q wave of the lead II electrocardiogram, whichever came first.lg The hemodynamic findings at cardiac catheterization were graded according to criteria modified from Ruzyllo et al.20 A good repair was defined as follows: (1) no ventricular septal
defect; (2) a peak systolic ejection gradient across the right ventricular outflow tract of 40 mm Hg or less or a peak right
ventricular systolic pressure of 50 percent or less of systemic pressure,2 or both. A fair repair was defined as (1) a residual ventricular septal defect with a pulmonary to systemic flow ratio of 1.5:1 or less; (2) a peak systolic ejection gradient across the right ventricular outflow tract of 60 mm Hg or less or a peak right ventricular systolic pressure of 75 percent or less of systemic pressure, or both. A repair was considered poor if there were (1) a residual ventricular septal defect with a pulmonary to systemic flow ratio greater than 1.5:1, and (2) a peak systolic ejection gradient across the right ventricular outflow tract greater than 60 mm Hg or a peak right ventricular systolic pressure greater than 75 percent of systemic pressure, or both. These three hemodynamic categories were correlated with the electrocardiographic groups. Statistical analyses were carried out using Student’s t test for grouped data.
Results His bundle electrograms (Tables I and II, Fig. 1): The 14 control patients had a mean A-H interval of 84.4 f 28 msec (k standard deviation) and an H-V interval of 35.8 f 7.1 msec. These intervals are similar to normal values for age (Fig. 1).21-24 Patients in Group A generally had normal His bundle electrographic intervals; after correction for age and heart rate, the A-H interval was prolonged in five patients with first degree A-V block; in the remainder, it was normal (77.7 f 21.6 msec). In all 44 patients in Group A the H-V interval was normal (39.5 f 7.2 msec). Patients in both Groups B and D had an A-H interval not significantly different from that of the control group (97.2 f 26.2 and 79.5 f 28.2 msec, respectively). Patients in Group C had a prolonged A-H interval (160.0 f 32.4 msec) that was nearly twice the value recorded in the control group and the other three groups. The H-V interval was significantly prolonged, by comparison with control values, in Groups B (48.8 f 10.7 msec), C (58.8 f 10.6 msec) and D (57.8 f 16.4 msec). One patient (Case 2) had both bifascicular block and transient complete A-V block but was included only in group B; he was 7 9/12 years old when he underwent correction of tetralogy of Fallot. In the operating room, transient complete A-V block appeared for several minutes. The His bundle recording 1 l/2 years later disclosed normal A-V conduction times of the A-H (65 msec) and H-V (46 msec) intervals. A second patient (Case 8) underwent initial repair at age 112/12 years. For several minutes while still in the operating room, he had transient complete heart block. After A-V conduction resumed in the intensive care unit, trifascicular block was noted in the surface electrocardiogram. At recatheterization 9 11/12 years later the His bundle electrogram disclosed a prolonged H-V interval (71 msec). He died at reoperation for a large residual ventricular septal defect and pulmonary stenosis at age 212112 years. Patient 14 had transient complete heart block for 3 weeks after operation (age 11 lo/12 years). At age 20 a His bundle study disclosed 2:l H-V block (infraHis) at an atria1 pacing rate of 125/min. Administration of atropine shortened A-H conduction slightly but did not alter the response of the H-V interval to atria1 pacing. In Patient 9 an initial operation at age 9 9/12 years yielded a poor hemodynamic result and the electrocardiographic pattern of trifascicular block. Reoperation 2 years later for a residual ventricular septal defect and pulmonary stenosis resulted in a good hemodynamic repair and a normal H-V interval at rest. With atria1 pacing at a rate of llO/min, 2:l A-H A-V block
March 1978
The Amorlcan Journal of CARDIOLOGY
Volume 41
553
H-V INTERVAL AFTER REPAIR OF TETRALOGY OF FALLOT-HOUGEN ET AL.
TABLE I Summary of Data in Groups B, C and D Postoperative Electrocardiogram CtRS AXIS P-R Interval Frontal QRS VI (seconds) Pattern Plane
Case no.
Hemodynamic Result
Intervals A-H H-V (msec) (msec)
Outcome
Right Atrial Pacino
...
Group 6 (bifascicular block) 0.14 0.18 0.16
RBBB RBBB
-90 -60 -45
Good Poor Fair
118 t
0.14 0.18
RBBB
-150 -120
Good Poor
129 82
S’
Grout C ftrifascicular block) 7
0.22
RBBB
-100
Poor
166 153
55 87
Alive Dead
: 10
0.22 0.26 0.26
RBBB RBBB
-90 -45
P-G Poor Poor
150 121 210
44 71 57
Dead Alive Alive
5:
Alive
60 77
Alive
142
Alive
Supra-&
block
...
Group 0 (transient complete heart block) :: ::
0.18 0.14 0.16 0.18
RBBB RBBB RBBB
Poor Good Good
+120 +90 +135 +90
Good
Ei 1:;
... Infra&‘block
Other’ 15
0.18
RBBB
+210
Poor
89
This patient had transient bifascicular block postoperatively for 10 days but at follow-up study manifested right bundle branch block, first degree A-V block and a clockwise frontal plane loop in the vectorcardiogram. P --+ G = poor after initial repair; good after reoperation. l
(supra-His or within the A-V node) developed while the H-V interval remained constant. A fifth patient (Case 15) had transient bifascicular block for 10 days after an initial repair at age 7 4/12 years. Follow-up catheterization 11 months later revealed a large ventricular septal defect and pulmonary stenosis. The His bundle electrogram demonstrated an A-H interval of 86 msec and a markedly prolonged H-V interval of 142 msec (Fig. 2). Neither the scalar electrocardiogram nor the vectorcardiogram revealed bifascicular block. Reoperation was successful.
His bundle electrogram versus surface electrocardiogram: In this series, 60 percent (9 of 15) of the
TABLE ii His Bundle Eiectrographic intervals Related to Electrocardiographic Group Intervals (mean f SD) H-V (msec) A-H (msec)
Group
CAontro :t B :
5 :
Other
1
84.4 77.7 f 28.0 21.6+ 97.2 f 26.2 160.0 79.5 f 28.2 32.4 78
39.5 f 7.1 35.8 7.2 48.8 f 57.8 58.8 f 142
10.7 10.6 16.4
Pvalue’ H-V
..
