Effects of left ventricular asynchrony on time constant and extrapolated pressure of left ventricular pressure decay in coronary artery disease

To elucidate the effects of ventricular asynchrony with of without myocardial ischemia on the time constant of left ventricular pressure decay and asymptote, that is, the level to which pressure would decrease if isovolumic pressure decrease continued infinitely, left ventriculography and pressure measurements were investigated in 14 normal subjects and 25 patients with coronary artery disease. Ventricular asynchrony was quantitated by the segmental area-time curve.This study consisted of two parts. 1) After a right atrial pacing stress test, the time constant and asymptote remained unchanged in eight normal subjects. In 18 patients with coronary artery disease and pacing-induced angina, asynchrony increased, the time constant was prolonged (64 ± 13 to 94 ± 17 ms, p < 0.01) and the asymptote decreased ( − 22 ± 10 to − 46 ± 20 mm Hg, p < 0.01) after the pacing. 2) During right ventricular pacing at 80, 100 and 120 beats/min in the patients, asynchrony increased and the time constant was prolonged (55 ± 7 versus 70 ± 10, 47 ± 11 versus 66 ± 19, 36 ± 7 versus 53 ± 13 ms, respectively, p < 0.01 versus right atrial pacing), whereas the asymptote was unchanged in six normal subjects compared with the value during right atrial pacing at each pacing rate. In seven patients with coronary artery disease, right ventricular pacing at 80,100 and 120 beats/min also produced an increase in the time constant, while the asymptote was unchanged.Thus, prolongation of the time constant of left ventricular pressure decay may result from ventricular asynchrony even in the absence of myocardial ischemia. In contrast, the asymptote (extrapolated pressure at infinity of left ventricular pressure decay) may decrease during myocardial ischemia irrespective of ventricular asynchrony. The nature of left ventricular pressure decay can be characterized not only by time constant but also by the asymptote