Influence of post-extrasystolic potentiation on left ventricular function estimated by means of systolic time intervals.

Systolic time intervals were measured in 50 patients with frequent premature ventricular beats. The patients were divided into two groups: group I included those which showed in the beat that preceded an extrasystole a pre-ejection period/left ventricular ejection time (PEP/LVET) ratio greater than or equal to 0.43, and group II with PEP/LVET ratio greater than 0.44. Systolic time intervals recorded during post-extrasystolic potentiation were compared with those measured in the preextrasystolic complex. Also the measured intervals were tested against the hourly rate of premature beats obtained by electrocardiographic telemetric monitoring. The results confirmed the following results of previous reports: a) ventricular premature beats are followed by sinus-potentiated contractions inversely related to the coupling interval and dependent on adequate compensatory pauses; b) potentiated contractions are greater in patients with ventricular dysfunction. No relationship was found between left ventricular performance and the rate of premature beats. It is concluded that the effect of an antiarrhythmic intervention on the left ventricular function might be adequately evaluated by means of systolic time intervals and provoked post-extrasystolic potentiation, with the advantage of using totally non-invasive procedures.