Augmentation of early diastolic filling by left ventricular postextrasystolic contraction

Abstract

In order to characterize the relationship between augmented left ventricular systolic contractility and early diastolic function, we measured left ventricular volume, transmitral pressure, and transmitral flow in seven anesthetized, closed-chest dogs, using angiographic, micromanometric, and Doppler echocardiographic techniques at baseline and in the cycle following an electrically induced, premature ventricular contraction. Compared with normal sinus beats, postextrasystolic contraction resulted in significant increases in peak aortic pressure (111 ±17 to 121 ± 21 mm Hg), the rate of rise of the left atrial pressure V wave (16 ± 3 to 24 ± 4 mm Hg/s), the first crossover point of atrial and ventricular pressures (4.4 ± 0.8 to 4.8 ± 0.8 mm Hg), the early maximum transmitral pressure gradient (3.8 ± 0.5 to 4.8 ± 0.8 mm Hg), the rate of decline of the left atrial pressure V wave (Y descent) (-43 ± 7 to −52 ±6 mm Hg/s), the height (4.3 ± 0.4 to 5.5 ± 0.5 mm Hg) and the rate of increase of the left ventricular pressure F wave (93 ± 16 to 109 ± 20 mm Hg/s), and the area of the reversed pressure gradient between the second and third points of crossover of left atrial and ventricular pressures (160 ± 29 to 216 ± 53 mm Hg/ms). Significant decreases were recorded in end-systolic volume (34 ± 7 to 25 ± 5 mL), the minimum pressure reached following the peak of the left atrial C wave (nadir of X' descent) (2.0 ± 0.8 to 0.7 ± 0.9 mm Hg), and in minimum left atrial (0.8 ± 1.4 to 0.1 ±1.5 mm Hg) and minimum left ventricular pressures (-0.8 ± 0.8 to −2.1 ±1.0 mm Hg). Postextrasystolic contraction also induced significant increases in acceleration (839 ± 118 to 1108 ± 240 cm/s2), deceleration (597 ± 95 to 849 ± 213 cm/s2), and the maximum velocity of transmitral flow reached during early diastolic filling (50 ± 4 to 65 ± 9 cm/s). All differences are significant at the 0.05 level. These observations are consistent with the hypothesis that at reduced end-systolic volumes, left ventricular myocardial storage of elastic energy is augmented, leading to increased ventricular recoil, which is manifested as a diminished minimum left ventricular pressure, an increased early transmitral pressure gradient, and increased early diastolic transmitral flow acceleration and peak velocity. The incremental return to baseline of the transmitral pressure gradient-flow pattern during the serial beats following postextrasystolic contraction suggests that ventricular recoil and suction occur in the basal state.