Prophylactic Permanent Pacemakers for Patients with Chronic Bundle Branch Block
ROBERTW. PETERS, M.D. MELVIN M. SCHEINMAN, M.D. GUNNARD MODIN, B.S. JUDY O’YOUNG. B.S. CAROLYN A. SOMELOFSKI, M.S. CAROLYN MIES, B.S. San Francisco, California
From the Medical Service, San Francisco General Hospital Medical Center, and the Department of Medicine, University of California, San Francisco, California. This study was supported in part by U.S. Public Health Service Grant HL 20238. This work was done during Dr. Scheinman’s tenure as an American Heart Association Teaching Scholar in Cardiology. Requests for reprints should be addressed to Dr. Robert W. Peters, 5 H 17. San Francisco General Hospital Medical Center, 1001 Potrero Avenue, San Francisco, California 94110. Manuscript accepted january 17,1979.
976
His bundle recordings were obtained in 189 patients with chronic bundle branch block, and the patients were followed for a mean of approximately 20 months. Forty patients underwent prophylactic pacemaker insertion (group II) and 149 did not (group I). There was no significant difference between the two groups at the time of entry into the study with regard to mean age, serum cholesterol or the incidence of smoking, diabetes, hypertension, coronary artery disease or congestive heart failure. The patients in group II had a significantly higher incidence of transient neurologic symptoms (30 of 40,75 per cent, versus 79 of l&$52 per cent, p < 0.05) and longer mean infranodal conduction time (79 f 25 versus 81 f 20 msec, p < 0.001). Eleven patients died before symptom relief could be assessed. More paced patients (group II) had relief of neurologic symptoms compared with the unpaced group (18 of 25,72 per cent, versus 38 of 73,49 per cent), but the difference was not quite statistically significant (0.1 < p > 0.05). There was no significant difference between the two groups in the total mortality or the incidence of sudden death. Nineteen of 21 sudden deaths occurred in patients with coronary artery disease and/or congestive heart failure. In conclusion, (1) prophylactic pacemaker insertion in a subset of largely symptomatic patients with chronic bundle branch block and long H-Q time did not protect against sudden death; the incidence of this complication appears to be related to the type and severity of underlying heart disease; (2) presenting neurologic symptoms may be an inadequate guide to assess the need for permanent pacing in bundle branch block. A subset of patients with electrocardiographic findings of bundle branch block appear to be at increased risk for the development of high grade atrioventricular (AV) block [l-5] or sudden death [6,7]. In a previous study from our laboratory [8], patients with chronic bundle branch block and marked prolongation of the infranodal conduction time (170 msec) appeared to be at increased risk for progression to high grade block. In addition, we found that patients in this subgroup who had associated moderate or severe congestive heart failure were also at increased risk for sudden death. These findings suggested that permanent prophylactic pacing for patients with marked prolongation of infranodal conduction time might be effective in aborting these complications. Reported herein are the results of long-term prospective follow-up of 40 patients with chronic bundle branch block who underwent prophylactic permanent pacemaker insertion (group I]. For the purposes of the study, the term prophylactic pacing is defined as permanent pacing in the absence of documented type II second degree
June 1979 The American Journal of Medicine
Volume 86
PROPHYLACTIC PERMANENT PACEMAKERS-PETERS ET AL.
or complete AV block. In addition, the clinical and follow-up characteristics of this group are compared with those of a large group of patients with bundle branch block who did not undergo pacemaker insertion (group II] but who were also followed prospectively; special emphasis is placed on the relief of neurologic symptoms, over-all mortality, and the incidence of cardiovascular and sudden death.
Haenszel method is a test for the association of two factors [of a binary nature] for data from retrospective or prospective studies. The method differs from a simple chi-square analysis in that adjustments are made for associated (control) factors. The significance test is a test of a consistent association in the same direction over the various subclassifications between the two study groups. The relative risk is the weighted the relative risk of the various subclassifications.
average of
RESULTS MATERIALS AND METHODS The methods used in this study were described previously [8]. In brief, this study was part of an ongoing collaborative interhospital prospective investigation of patients with chronic bundle branch block in the San Francisco Bay Area. At the time of entry into the study, a complete medical history, physical examination, chest roentgenograms and serum lipid determinations were obtained. In addition, a His bundle electrogram was obtained using standard techniques [9]. In almost all instances, the administration of antiarrhythmic medications, with the exception of digitalis, was stopped prior to study. Specifically excluded from the study were patients with bundle branch block and acute myocardial infarction or second or third degree AV block. Patients were seen every three months either in the Pacemaker and Arrhythmia Clinic at the San Francisco General Hospital Medical Center or by private physicians. Specific information relative to the presence of neurologic symptoms and the type and dose of any antiarrhythmic agents was noted on each visit. Blood concentrations of drug were measured when clinically indicated. Patients who were unable to keep their regular follow-up appointments were called or, if necessary, visited by a public health nurse (C.S.].All deaths were investigated by discussions with the patient’s physician, family members and witnesses present at the time of death. In addition, death certificates, hospital records and the results of postmortem examinations (when available] were analyzed. One hundred forty-nine patients (group 11with chronic bundle branch block did not undergo pacemaker insertion and were followed as outlined herein. Forty patients (group II) underwent prophylactic pacemaker insertion. None of these patients showed evidence of second or third degree AV block despite repeated continuous electrocardiographic monitoring. Pacemaker insertion was performed at the discretion of the referring physician on the basis of abnormalities in the infranodal conduction time (10 patients] or a combination of electrophysiologic abnormalities and neurologic symptoms (30 patients). In four of the asymptomatic patients, the nature of the occupation proved to be an important factor in the decision to insert a pacemaker. These patients were seen regularly either by their private physicians dr In the Pacemaker Clinic at the San Francisco General Hospital Medical Center. In addition, follow-up included periodic telephone transmission of the pacemaker rate and stimulus characteristics.
StatisticalMethods. All data were stored on punch cards and later retrieved using 360/75 computer. All square test, Fischer’s tel-Haenszel method
a program written for the IBM model nominal data were tested with the chiexact probability test [lo] or the Manof analysis [ll,lZ]. Briefly, the Mantel-
From March 1972 until December 1977, a total of 224 patients were entered into the study. Thirty-five patients were excluded for the following reasons: less than three months follow-up time (20 patients), insufficient follow-up information available (four patients) or documented progression to second or third degree AV block (11 patients). Mean follow-up time of the 189 patients in the study was approximately 20 months. Intake Clinical and Electrophysiologic Data (Tables I and II). The relevant data for patients with (group II] or without [group I) prophylactic pacemaker insertion are summarized in Tables I and II. There was no sig-
nificant difference in mean age, serum cholesterol level or incidence of hypertension, diabetes, coronary artery disease or in congestive heart failure between the two groups. Congestive heart failure was diagnosed on the basis of the medical history, physical findings and chest roentgenograms. Only those patients fulfilling the criteria of the New York Heart Association functional cardiac status III or IV were included [l3]. The incidence of syncope and of all transient neurologic symptoms (defined as episodes of syncope, dizziness or seizures] was significantly higher in group II than in
group I (p< 0.001and p < 0.05, respectively). There was no significant difference in the incidence of the type of bundle branch block pattern, in QRS duration or in the number of patients with QRS intervals >160 msec between the two groups. In contrast, mean AV nodal [A-H) and mean infranodal conduction (H-Q) times were significantly greater in group II than in group I (p < 0.05 and p
ROBERTW. PETERS, M.D. MELVIN M. SCHEINMAN, M.D. GUNNARD MODIN, B.S. JUDY O’YOUNG. B.S. CAROLYN A. SOMELOFSKI, M.S. CAROLYN MIES, B.S. San Francisco, California
From the Medical Service, San Francisco General Hospital Medical Center, and the Department of Medicine, University of California, San Francisco, California. This study was supported in part by U.S. Public Health Service Grant HL 20238. This work was done during Dr. Scheinman’s tenure as an American Heart Association Teaching Scholar in Cardiology. Requests for reprints should be addressed to Dr. Robert W. Peters, 5 H 17. San Francisco General Hospital Medical Center, 1001 Potrero Avenue, San Francisco, California 94110. Manuscript accepted january 17,1979.
976
His bundle recordings were obtained in 189 patients with chronic bundle branch block, and the patients were followed for a mean of approximately 20 months. Forty patients underwent prophylactic pacemaker insertion (group II) and 149 did not (group I). There was no significant difference between the two groups at the time of entry into the study with regard to mean age, serum cholesterol or the incidence of smoking, diabetes, hypertension, coronary artery disease or congestive heart failure. The patients in group II had a significantly higher incidence of transient neurologic symptoms (30 of 40,75 per cent, versus 79 of l&$52 per cent, p < 0.05) and longer mean infranodal conduction time (79 f 25 versus 81 f 20 msec, p < 0.001). Eleven patients died before symptom relief could be assessed. More paced patients (group II) had relief of neurologic symptoms compared with the unpaced group (18 of 25,72 per cent, versus 38 of 73,49 per cent), but the difference was not quite statistically significant (0.1 < p > 0.05). There was no significant difference between the two groups in the total mortality or the incidence of sudden death. Nineteen of 21 sudden deaths occurred in patients with coronary artery disease and/or congestive heart failure. In conclusion, (1) prophylactic pacemaker insertion in a subset of largely symptomatic patients with chronic bundle branch block and long H-Q time did not protect against sudden death; the incidence of this complication appears to be related to the type and severity of underlying heart disease; (2) presenting neurologic symptoms may be an inadequate guide to assess the need for permanent pacing in bundle branch block. A subset of patients with electrocardiographic findings of bundle branch block appear to be at increased risk for the development of high grade atrioventricular (AV) block [l-5] or sudden death [6,7]. In a previous study from our laboratory [8], patients with chronic bundle branch block and marked prolongation of the infranodal conduction time (170 msec) appeared to be at increased risk for progression to high grade block. In addition, we found that patients in this subgroup who had associated moderate or severe congestive heart failure were also at increased risk for sudden death. These findings suggested that permanent prophylactic pacing for patients with marked prolongation of infranodal conduction time might be effective in aborting these complications. Reported herein are the results of long-term prospective follow-up of 40 patients with chronic bundle branch block who underwent prophylactic permanent pacemaker insertion (group I]. For the purposes of the study, the term prophylactic pacing is defined as permanent pacing in the absence of documented type II second degree
June 1979 The American Journal of Medicine
Volume 86
PROPHYLACTIC PERMANENT PACEMAKERS-PETERS ET AL.
or complete AV block. In addition, the clinical and follow-up characteristics of this group are compared with those of a large group of patients with bundle branch block who did not undergo pacemaker insertion (group II] but who were also followed prospectively; special emphasis is placed on the relief of neurologic symptoms, over-all mortality, and the incidence of cardiovascular and sudden death.
Haenszel method is a test for the association of two factors [of a binary nature] for data from retrospective or prospective studies. The method differs from a simple chi-square analysis in that adjustments are made for associated (control) factors. The significance test is a test of a consistent association in the same direction over the various subclassifications between the two study groups. The relative risk is the weighted the relative risk of the various subclassifications.
average of
RESULTS MATERIALS AND METHODS The methods used in this study were described previously [8]. In brief, this study was part of an ongoing collaborative interhospital prospective investigation of patients with chronic bundle branch block in the San Francisco Bay Area. At the time of entry into the study, a complete medical history, physical examination, chest roentgenograms and serum lipid determinations were obtained. In addition, a His bundle electrogram was obtained using standard techniques [9]. In almost all instances, the administration of antiarrhythmic medications, with the exception of digitalis, was stopped prior to study. Specifically excluded from the study were patients with bundle branch block and acute myocardial infarction or second or third degree AV block. Patients were seen every three months either in the Pacemaker and Arrhythmia Clinic at the San Francisco General Hospital Medical Center or by private physicians. Specific information relative to the presence of neurologic symptoms and the type and dose of any antiarrhythmic agents was noted on each visit. Blood concentrations of drug were measured when clinically indicated. Patients who were unable to keep their regular follow-up appointments were called or, if necessary, visited by a public health nurse (C.S.].All deaths were investigated by discussions with the patient’s physician, family members and witnesses present at the time of death. In addition, death certificates, hospital records and the results of postmortem examinations (when available] were analyzed. One hundred forty-nine patients (group 11with chronic bundle branch block did not undergo pacemaker insertion and were followed as outlined herein. Forty patients (group II) underwent prophylactic pacemaker insertion. None of these patients showed evidence of second or third degree AV block despite repeated continuous electrocardiographic monitoring. Pacemaker insertion was performed at the discretion of the referring physician on the basis of abnormalities in the infranodal conduction time (10 patients] or a combination of electrophysiologic abnormalities and neurologic symptoms (30 patients). In four of the asymptomatic patients, the nature of the occupation proved to be an important factor in the decision to insert a pacemaker. These patients were seen regularly either by their private physicians dr In the Pacemaker Clinic at the San Francisco General Hospital Medical Center. In addition, follow-up included periodic telephone transmission of the pacemaker rate and stimulus characteristics.
StatisticalMethods. All data were stored on punch cards and later retrieved using 360/75 computer. All square test, Fischer’s tel-Haenszel method
a program written for the IBM model nominal data were tested with the chiexact probability test [lo] or the Manof analysis [ll,lZ]. Briefly, the Mantel-
From March 1972 until December 1977, a total of 224 patients were entered into the study. Thirty-five patients were excluded for the following reasons: less than three months follow-up time (20 patients), insufficient follow-up information available (four patients) or documented progression to second or third degree AV block (11 patients). Mean follow-up time of the 189 patients in the study was approximately 20 months. Intake Clinical and Electrophysiologic Data (Tables I and II). The relevant data for patients with (group II] or without [group I) prophylactic pacemaker insertion are summarized in Tables I and II. There was no sig-
nificant difference in mean age, serum cholesterol level or incidence of hypertension, diabetes, coronary artery disease or in congestive heart failure between the two groups. Congestive heart failure was diagnosed on the basis of the medical history, physical findings and chest roentgenograms. Only those patients fulfilling the criteria of the New York Heart Association functional cardiac status III or IV were included [l3]. The incidence of syncope and of all transient neurologic symptoms (defined as episodes of syncope, dizziness or seizures] was significantly higher in group II than in
group I (p< 0.001and p < 0.05, respectively). There was no significant difference in the incidence of the type of bundle branch block pattern, in QRS duration or in the number of patients with QRS intervals >160 msec between the two groups. In contrast, mean AV nodal [A-H) and mean infranodal conduction (H-Q) times were significantly greater in group II than in group I (p < 0.05 and p
