Comparative effects of overdrive on sinus and subsidiary pacemaker function Jay Jordan, M.D. Iwao Yamaguchi, M.D. William J. Mandel, M.D. Avile E. McCullen Los Angeles, Calif.
Recent electrophysiological studies have accumulated significant data concerning the behavior of the normal and diseased sinus node in response to premature atrial systoles and atrial overdrive pacing. 1-1~Specifically, the duration of sinus node recovery time after rapid atrial pacing has been used as a means of diagnosing the clinical entity called the sick sinus syndrome. 11-15 In contrast, little literature is available on the effects of premature systoles and overdrive pacing on lower pacemaker sites within the A-V junctional tissue and the distal conduction system. ~6-~ The purpose of the present study is to investigate the potential differential effects of overdrive pacing on the recovery time of the sinus pacemaker and subsidiary escape pacemakers. Methods Patient studies. All patients were studied in the preprandial state after admission and observation in the coronary-observation unit. All s~udies were conducted in the cardiac catheterization laboratory. A No. 6 Fr. four-polar catheter was passed through an antecubital vein into the high right atrium and a No. 6 Fr tripolar catheter was passed through the right femoral vein into the right ventricle at the level of the bundle of His. Surface electrocardiogram (ECG), intraatrial, bundle of His, and intraventricular electrical activity were then recorded on a photoFrom the Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, Calif. This study was supported in part by United States Public Health Grant No. HL 17651-01. Received for publication Feb. 9, 1976. Reprint requests: Jay Jordan, M.D., Department of Cardiology, Cedars-Sinai Medical Center, 4833 Fountain Ave., Los Angeles, Calif. 90029.
March, 1977, Vol. 93, No. 3, pp. 367-374
graphic oscillographic recorder* at a paper speed of 100 mm. per second. Atrial pacing at 90, 110, 130, 150, and 170 beats per minute was carried out for 30 second periods and then abruptly terminated. Sinus node recovery time was measured as the time elapsing from the last pacemaker spike to the appearance of the next atrial depolarization on the intra-atrial electrogram. P-wave configuration on the surface ECG was used to ascertain that the first, escape beat terminating the pause was indeed sinoatrial in origin. Subsequently, the femoral catheter was repositioned at the apex of the right ventricle and a similar pacing protocol carried out utilizing rates of 90 to 150 per minute. Patient population. Seven patients, ranging in age from 7 to 81 years, with chronic advanced A-V block, were studied. Two patients had congenital heart block, one patient had heart block secondary to aortic valve disease, and four patients had idiopathic heart block. No patient was taking antiarrhythmic drugs or other medication known to interfere with sinus node or subsidiary escape pacemaker function. Two patients had ECG evidence of old myocardial infarction and two patients had clinical evidence for left ventricular dysfunction. No patient had a febrile illness, thyroid disease, hypovolemia, symptomatic anemia, pulmonary disease, arterial hypoxia, acid-base disturbances, or electrolyte imbalances. Dog studies. Five healthy mongrel dogs (15 to 20 kilograms) were premedicated with morphine sulfate, 2 mg. per kilogram, given as an intramuscular injection. After tracheal intubation, the dogs were put on assisted ventilation and general *Electronics for Medicine, DRS.
American Heart Journal
367
J o r d a n et al.
B. DOGS
A. HUMANS
/•
I000
CO
w
i~
I-~'~
80G
60C
800 N=4
N'6
N=?
N=7
N=2
40[
600 I 90
I I10
I 130
I 150
I 130
I 170
I , 150
I 170
I 190
I 210
PACING RATE FOR 30 SECONDS beats/min Fig. 1. (A) The relationship between sinus node recovery time and the rate of atrial overdrive pacing in man. The mean sinus recovery time remains essentially constant over a wide range of pacing rates. (B) The relationship between sinus node recovery time and rate of atrial overdrive pacing in dogs. The mean sinus node recovery time remains essentially constant over a wide range of pacing rates.
B. SUBSIDIARY PACEMAKER
A. SINUS NODE
28,000
i,
- - 5o seconds -I minute -- 3 minutes p
Recent electrophysiological studies have accumulated significant data concerning the behavior of the normal and diseased sinus node in response to premature atrial systoles and atrial overdrive pacing. 1-1~Specifically, the duration of sinus node recovery time after rapid atrial pacing has been used as a means of diagnosing the clinical entity called the sick sinus syndrome. 11-15 In contrast, little literature is available on the effects of premature systoles and overdrive pacing on lower pacemaker sites within the A-V junctional tissue and the distal conduction system. ~6-~ The purpose of the present study is to investigate the potential differential effects of overdrive pacing on the recovery time of the sinus pacemaker and subsidiary escape pacemakers. Methods Patient studies. All patients were studied in the preprandial state after admission and observation in the coronary-observation unit. All s~udies were conducted in the cardiac catheterization laboratory. A No. 6 Fr. four-polar catheter was passed through an antecubital vein into the high right atrium and a No. 6 Fr tripolar catheter was passed through the right femoral vein into the right ventricle at the level of the bundle of His. Surface electrocardiogram (ECG), intraatrial, bundle of His, and intraventricular electrical activity were then recorded on a photoFrom the Department of Cardiology, Cedars-Sinai Medical Center, Los Angeles, Calif. This study was supported in part by United States Public Health Grant No. HL 17651-01. Received for publication Feb. 9, 1976. Reprint requests: Jay Jordan, M.D., Department of Cardiology, Cedars-Sinai Medical Center, 4833 Fountain Ave., Los Angeles, Calif. 90029.
March, 1977, Vol. 93, No. 3, pp. 367-374
graphic oscillographic recorder* at a paper speed of 100 mm. per second. Atrial pacing at 90, 110, 130, 150, and 170 beats per minute was carried out for 30 second periods and then abruptly terminated. Sinus node recovery time was measured as the time elapsing from the last pacemaker spike to the appearance of the next atrial depolarization on the intra-atrial electrogram. P-wave configuration on the surface ECG was used to ascertain that the first, escape beat terminating the pause was indeed sinoatrial in origin. Subsequently, the femoral catheter was repositioned at the apex of the right ventricle and a similar pacing protocol carried out utilizing rates of 90 to 150 per minute. Patient population. Seven patients, ranging in age from 7 to 81 years, with chronic advanced A-V block, were studied. Two patients had congenital heart block, one patient had heart block secondary to aortic valve disease, and four patients had idiopathic heart block. No patient was taking antiarrhythmic drugs or other medication known to interfere with sinus node or subsidiary escape pacemaker function. Two patients had ECG evidence of old myocardial infarction and two patients had clinical evidence for left ventricular dysfunction. No patient had a febrile illness, thyroid disease, hypovolemia, symptomatic anemia, pulmonary disease, arterial hypoxia, acid-base disturbances, or electrolyte imbalances. Dog studies. Five healthy mongrel dogs (15 to 20 kilograms) were premedicated with morphine sulfate, 2 mg. per kilogram, given as an intramuscular injection. After tracheal intubation, the dogs were put on assisted ventilation and general *Electronics for Medicine, DRS.
American Heart Journal
367
J o r d a n et al.
B. DOGS
A. HUMANS
/•
I000
CO
w
i~
I-~'~
80G
60C
800 N=4
N'6
N=?
N=7
N=2
40[
600 I 90
I I10
I 130
I 150
I 130
I 170
I , 150
I 170
I 190
I 210
PACING RATE FOR 30 SECONDS beats/min Fig. 1. (A) The relationship between sinus node recovery time and the rate of atrial overdrive pacing in man. The mean sinus recovery time remains essentially constant over a wide range of pacing rates. (B) The relationship between sinus node recovery time and rate of atrial overdrive pacing in dogs. The mean sinus node recovery time remains essentially constant over a wide range of pacing rates.
B. SUBSIDIARY PACEMAKER
A. SINUS NODE
28,000
i,
- - 5o seconds -I minute -- 3 minutes p
