Abstract
Left ventricular contraction, relaxation, and diastolic mechanics were examined in subjects after postextrasystolic potentiation and compared with results during supine bicycle exercise. Twelve patients had ventricular extrasystoles induced during biplane left ventricular cineangiography (PES Group). Six patients with no or minimal cardiovascular disease underwent exercise (Exercise Group). From simultaneous high-fidelity pressure curves the time constant of relaxation (T), a theoretical baseline for isovolumic pressure decay (PB), and the lowest diastolic pressure (PL) were determined. Frame-by-frame volume analysis was completed in 6 patients from the PES Group and 4 in the Exercise Group to quantitate filling rates and to construct diastolic pressure-volume relations. In the PES Group, the ejection fraction increased from 65 to 74% (p In the Exercise Group, the ejection fraction increased from 65 to 75% (p Postextrasystolic potentiation, like dynamic exercise, enhances shortening and augments restoring forces by producing a smaller end-systolic chamber. Yet, postextrasystolic potentiation delays inactivation and prolongs relaxation. Diastolic mechanics (early diastolic pressure, filling, pressure-volume relation) are not subsequently altered, suggesting that enhanced restoring forces counterbalance the delayed inactivation. With exercise, diastolic filling is enhanced both by more rapid pressure decay and by increased restoring forces. Thus, diastolic mechanics can be dissociated from systolic and are determined by the nature of the inotropic stimulus.
Published Version
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