Effects of coronary occlusion on early ventricular diastolic events in conscious dogs

Abstract

A left ventricular (LV) micromanometer and ultrasonic dimension gauge in control (CS) and ischemic segments (IS) were implanted in 9 dogs 7-10 days before study. Early (10-20 s) during 1 min coronary occlusions (CO), the IS showed decreased shortening and a late systolic bulge, synchronous with exaggerated late systolic shortening (LSS) in the CS. These late systolic events in both segments interrupted the exponential fall of LV pressure during isovolumetric relaxation. Peak -dP/dt [change in pressure with time] decreased markedly by 38.4%, time to peak -dP/dt decreased by 7.2% and peak +dP/dt decreased by 19.9% (all P < 0.01). Later (30-60 s of CO), the IS showed early sustained holosystolic bulging, LSS in the CS disappeared, and peak -dP/dt and time to peak -dP/dt approached control levels. At 60 s, peak +dP/dt remained decreased (P < 0.05), and the time constant (T) was increased by 20.5% (P < 0.01). The early marked reduction in peak -dP/dt reflected the effects of marked regional dyssynchrony. Holosystolic expansion of the IS compensated for these early effects, and depressed contractile function and relaxation in the IS were reflected by reduced peak +dP/dt and prolonged T. Ventricular dyssynchrony due to late systolic contraction and relaxation in different regions can produce marked effects on the linearity and maximal rate of pressure fall in the left ventricle.