Increase in the late diastolic filling force is associated with impaired transmitral flow efficiency in acute moderate elevation of left ventricular afterload.

OBJECTIVE: Analysis of intraventricular flow force and efficiency is a novel concept of quantitatively assessing left ventricular (LV) hemodynamic performance. We have parametrically characterized diastolic filling flow by early inflow force, late inflow force, and total inflow force and by vortex formation time (VFT), a fundamental parameter of fluid transport efficiency. The purpose of this study was to determine what changes in inflow forces characterize a decrease in diastolic blood transport efficiency in acute moderate elevation of LV afterload.
METHODS: In 8 open-chested pigs, the flow force and VFT parameters were calculated from conventional and flow Doppler echocardiographic measurements at baseline and during a brief (3-minute) moderate elevation of afterload induced by increasing the systolic blood pressure to 130% of the baseline value.
RESULTS: Systolic LV function decreased significantly during elevated afterload. Early inflow force did not significantly change, whereas late inflow force increased from 5,822.09 +/- 1,656.5 (mean +/- SD) to 13,948.25 +/- 9,773.96 dyne (P = .049), and total inflow force increased from 13,783.35 +/- 4,816.58 to 21,836.67 +/- 8,635.33 dyne (P = .031). Vortex formation time decreased from 4.09 +/- 0.29 to 2.79 +/- 1.1 (P = .0068), confirming suboptimal flow transport efficiency.
CONCLUSIONS: Even a brief moderate increase of LV afterload causes a significant increase in late diastolic filling force and impairs transmitral flow efficiency.