Frequency and Variability of Ventricular Premature Contractions—The Influence of Heart Rate and Circadian Rhythms

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Abstract
Present knowledge about arrhythmias is still too limited to prevent sudden cardiac death Long‐term ambulatory ECG monitoring should be the method of choice in further investigating and evaluating the possible relationships between the frequency of arrhythmias and heart rate (MR), circadian patterns, and effects of drugs Using a computer‐supported, semiautomatic anaiysis system, 77 patients with a mean premature ventricuiar contraction (PVC)‐rate of over 1% were monitored for 24 hours (group A). Ten other patients with PVC's of over 1% were monitored for up to 96 hrs each, continuousiy, to demonstrate the reproducibility of possible circadian PVC's and HR patterns (group B) Another group of 44 patients (group C) underwent long‐term ECG monitoring of 24 hrs before and during drug therapy with disopyramide (n = 15 pts, 200 mg tid), mexiletine (n = 13 pts, 200 mg t.i.d.), acebutoiol (n = 9 pts, 200 mg bid) and propafenon (n = 7 pts, 300 mg t i.d.) to judge the drug effects in relation to their specific chronotropic properties. In group A patients there was a significant correlation (r = ‐0 602) between mean PVC frequency and respective PVC variabilities The latter increase with a reduction of the PVC rate and vice versa A circadian pattern of HR and PVC's can be demonstrated in the majority of group A and B patients. By using Scheffe's test to determine the required PVC reduction, the statistical PVC reduction curve (p < 0 05) does not conform to the PVC‐aboiition curve (PVC beiow 1%) in group B patients If patients without circadian PVC/HR patterns are under antiarrhythmic therapy, they need a much higher mean PVC‐reduotion rate to reach the statistical significance level than patients without such a PVC and HR behavior. Drugs administered in Group C patients had different chronotropic effects Heart rate spectra were demonstrated for each antiarrhythmic drug used The distribution of arrhythmias, their variability, HR, circadian rhythm and the activity of antiarrhythmic drugs should be taken into account to narrow the gap between current antiarrhythmic treatment and the prevention of sudden cardiac death