The Spontaneous Variation in the Pattern of Ventricular Extrasystoles in Patients Recently Recovered from an Acute Myocardial Infarction

Twelve patients between the ages of 40 and 68 years with myocardial infarction 1-6 months earlier were subjected to 24 h of ambulatory ECG monitoring for 2 consecutive d. In six patients with an average of less than 5 ventricular extrasystoles (VE) per hour during the first day, the pattern of the arrhythmias was both quantitatively and qualitatively unchanged from day to day. In six patients with an average of greater than 60 VE/h the first day, the number of VE were reduced significantly from the first to second day--in four patients by greater than 50%. The variation was greater after a day-to-day comparison than within the individual days following the division of the 24 h into 6-h periods. In general, the ventricular arrhythmias varied less following a qualitative rather than a quantitative evaluation. The evaluation of the effect of an antiarrhythmic drug in postmyocardial infarction patients requires that a considerable spontaneous variation should be taken into account when the patient is to be used as his own control. If a duration of monitoring of 24 h is employed both prior to and after the commencement of treatment, then the ventricular arrhythmias must practically disappear before the antiarrhythmic effect may be said to be documented.