Characteristics of non-sustained ventricular tachycardia detected by ambulatory electrocardiography.

We analyzed non-sustained ventricular tachycardia (VT) observed during ambulatory electrocardiographic (ECG) monitoring in 21 subjects. The rate of VT was 160.7 +/- 2.3 beats/min and showed a moderate positive correlation (r = 0.61, p less than 0.01) with the preceding heart rate (81.8 +/- 1.0 beats/min). The prematurity index of VT was 1.118 +/- 0.015 and showed a moderate inverse correlation with the rate of VT (r = -0.64, p less than 0.01). The vulnerability index was 0.713 +/- 0.009. These indices of prematurity showed a wide distribution and the prematurity of ventricular ectopic beats may not be so significant as previously documented. The incidence of VT was higher in the morning and the evening and was reduced by sleep. The most frequent type of VT (25-/day) was observed only in patients with VT predominantly occurring during the day. We have therefore postulated that these diurnal variations in the frequency of VT may have important therapeutic and prognostic implications. In this study, we used the classification of VT based on the focus, the diurnal variation and the frequency of the tachycardia. Ambulatory ECG monitoring is useful in distinguishing the various types of VT and it is important to separate the various types of VT into several subgroups in order to classify grade the severity of VT.