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[Study concerning the effects of exercise on the frequency of ventricular premature contraction. A new classification
Abstract:
The effects of exercise on the frequency of ventricular premature contraction (VPC) and the clinical implications thereof were studied in 95 patients. Patients with ischemic heart disease and severe congestive heart failure were excluded from the study. The patients were divided into 7 groups according to changes in the frequency of VPC during and after exercise. Clinical background, exercise parameters and the efficacy of antiarrhythmic drugs were compared among these 7 groups. Plasma catecholamine concentration was measured in 34 patients, with a group of 12 healthy subjects serving as controls. An increase in the frequency of VPC both during and after exercise was observed in 16 patients (Group II). In comparison with the other groups, this group was older, and exhibited a higher incidence of underlying heart disease, lower tolerance to exercise and more serious ventricular arrhythmias. Beta-blockers were the most effective treatment for this group. However, plasma catecholamine concentration was not significantly higher in this group than it was in the other groups or the healthy subjects. A decrease in the frequency of VPC during exercise and an increase after exercise was observed in 25 patients (Group DI). This group also exhibited a high incidence of underlying heart disease and serious ventricular arrhythmias. The daily frequency of VPC was highest in this group. Class I and IV antiarrhythmic drugs were the most effective treatment. Although plasma catecholamine concentration was not significantly different from that of the other groups or the group of healthy subjects, a shorter QT interval was observed after exercise as compared with the healthy subjects. In this group, therefore, the mechanism of VPC may be related to a disturbance in the rate-adaptation of the QT interval, causing nonuniformity in the refractory period of the ventricular muscle. A decrease in the frequency of VPC during and after exercise was observed in 26 patients (Group DD). As compared with the other groups, this group was younger, and exhibited a lower incidence of underlying heart disease and a higher tolerance to exercise. This group was thus regarded as comprising the less severe cases. Seventeen patients showed no change in the frequency of VPC during exercise and an increase after exercise (Group UI). This group had the second highest average age and exhibited the lowest daily frequency of VPC. The incidence of underlying heart disease and serious ventricular arrhythmias fell between that of Groups IL/DI and Group DD.(ABSTRACT TRUNCATED AT 400 WORDS)