(Circulation. 1995;91:2371-2377.)
© 1995 American Heart Association, Inc.
Articles |
Long-term Temporal Patterns of Ventricular Tachyarrhythmias
From the Department of Medicine (Cardiology) (M.A.W., B.S.S., K.A.E.) and Department of Biostatistics (P.M.S.), Medical College of Virginia, McGuire Veterans Administration Medical Center (M.A.W., B.S.S., K.A.E.), Richmond; and Sentara Norfolk General Hospital (J.M.H., R.C.B.), Norfolk, Va.
Background Technological limitations have precluded investigation of long-term temporal patterns of ventricular tachyarrhythmia recurrences. Newer implantable cardioverter-defibrillators permit such analyses by accurately recording the time and date of tachycardia detections during long-term follow-up. This study tests the hypothesis that ventricular tachycardia occurrences are randomly distributed over time in individual patients.
Methods and Results The time and date of 727 episodes of
ventricular tachyarrhythmias were recorded from the data logs of 31
patients with implantable cardioverter-defibrillators followed for a
median of 177 days (range, 7 to 782 days). All patients had three or
more ventricular tachycardia detections and no detections from causes
other than ventricular arrhythmias. In 28 of 31 patients, the
distribution of the interdetection time intervals during follow-up
differed significantly (all P<.01) from an exponential
model distribution of interdetection intervals that assumed that
detections were equally likely to occur at any time during follow-up
(random). The Kolmogorov-Smirnov goodness-of-fit test was used to
compare sample and model distributions. In each patient, the nonrandom
distributions resulted from a preponderance of interdetection time
intervals that were shorter than predicted by the random model,
resulting in a temporal clustering of arrhythmic events. The
interdetection interval was 
1 hour and 91 hours for 55% and 78%
of all intervals, respectively. When only those episodes receiving
shock or antitachycardia pacing therapy were analyzed, 25 of 29
patients still manifested nonrandom distributions (all
P<.01). When only episodes with tachycardia rates >240
beats per minute were analyzed, 11 of 13 patients manifested nonrandom
distributions (all P<.01).
Conclusions Ventricular tachycardia detections and delivered antitachycardia therapies by implantable cardioverter-defibrillators are nonrandomly distributed throughout long-term follow-up in the majority of patients. The temporal clustering of these arrhythmic events may allow preemptive antiarrhythmic therapy and should be considered in the design of therapy based on suppression of spontaneous ventricular arrhythmias to statistically derived end points.
Key Words: tachyarrhythmias • defibrillation