Cardiac memory: a mechanical and electrical phenomenon.
Alessandrini, Renato S., David D. McPherson, Alan H. Kadish, Bonnie J.
Kane, Jeffrey J. Goldberger.
Division of Cardiology, Northwestern University Medical School,
Chicago, Illinois
APStracts 3:0530H, 1996.
Alterations in repolarization following prolonged periods of
ventricular pacing, termed cardiac memory, have been well documented.
Post-pacing changes in cardiac function have also been noted in
hypertrophic cardiomyopathy. This study was designed to evaluate the
effects of ventricular pacing on post-pacing diastolic function and
its relationship to repolarization changes. Eight subjects (mean age
76 years) with permanent pacemakers were enrolled in this study. Each
subject was evaluated at a fixed pacing rate with recording of
electrocardiographic and echocardiographic data. Seven sets of
measurements were performed in the same sequential pattern: 1) after
1 week of atrial pacing; 2) within 10 minutes after initiating
atrioventricular sequential pacing (ventricular pacing); 3) within 10
minutes after terminating 1 hour of ventricular pacing; 4) after 1
week of ventricular pacing; and 5) within 10 minutes, at 1 hour, and
at 24 hours following termination of ventricular pacing. All subjects
had repolarization changes characteristic of cardiac memory only
following 1 week of ventricular pacing. Changes in repolarization
parameters were accompanied by changes in peak left ventricular
filling rate (dD/dt/D; p=0.02) and isovolumic relaxation time (IVRT;
p=0.03) that at 24 hours approached baseline values. Correlations
existed between changes in the QT interval and IVRT (r=0.53, p=0.007)
and between changes in T wave amplitude and dD/dt/D (r=0.48, p=0.018)
following long term ventricular pacing. Thus, changes in both
repolarization and diastolic function persist following cessation of
ventricular pacing and lend support to the concept of electrical and
mechanical cardiac memory.
Received 24 September 1996; accepted in final form 25 November
1996.
APS Manuscript Number H861-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996