Postextrasystolic potentiation in man.

Postextrasystolic potentiation (PESP) is a pre- and afterload-independent property of the myocardium. Therefore it has been used to study left ventricular (LV) contractile state in patients with coronary heart disease and normals. Using a computer-controlled cardiac stimulator, regular rhythms with just above sinus frequency were applied to the right atrium and interrupted after every 20th beat by one shorter interval after varying delays. The next stimulus interval was corrected in such a way that the resulting R-R interval was the same as the basic R-R interval. Control of the postextrasystolic R-R interval is a prerequisite for meaningful and quantitative evaluation of PESP. Of 166 basic and postextrasystolic beats in 12 patients LV pressures (P), obtained with a catheter tipmanometer, were analyzed. There was no significant difference in enddiastolic P between pre- and postextrasystolic beats. Peak dP/dt, time to peak dP/dt, (dP/dt)/P at a left ventricular P of 50 mm Hg and Vmax were used as indices of left ventricular contractile state. It was found that on increasing prematurity of the extrasystolic beat, there was a progressive and reproducible increase of these indices (selfevidently a decrease in the case of the time to reach peak dP/dt). Using Vmax as an index of contractile state, no significant PESP could be demonstrated in the two patients with very enlarged left ventricular volumes and depressed ejection fractions. PESP, elicted in this (only allowable) way, is an integral, quantitative and reproducible method for LV contractility estimation in man.