MECHANICS OF INTRAVENTRICULAR FILLING - STUDY OF LV EARLY DIASTOLIC PRESSURE-GRADIENTS AND FLOW VELOCITIES

This study investigates mechanisms of left ventricular (LV) intracavit ary flow during early, rapid filling. In eight coronary artery disease patients with normal LV ejection fraction we recorded simultaneous LV apical and outflow tract pressures and intraventricular flow velociti es by color M-mode Doppler echocardiography. In five anesthetized dogs we also recorded left atrial pressure and LV volume by sonomicrometry . In patients, as the early diastolic mitral-to-apical filling wave ar rived at the apex, we observed an apex-outflow tract pressure gradient of 3.5 +/- 0.3 mmHg (mean +/- SE). This pressure gradient correlated with peak early apex-to-outflow tract flow velocity (r = 0.75, P < 0.0 5). The gradient was reproduced in the dog model and decreased from 3. 1 +/- 0.3 to 1.7 +/- 0.5 mmHg (P < 0.05) with caval constriction and i ncreased to 4.2 +/- 0.5 mmHg (P < 0.001) with volume loading. The pres sure gradient correlated with peak early transmitral flow (expressed a s time derivative of LV volume; r = 0.95) and stroke volume (r = 0.97) . In conclusion, arrival of the early LV filling wave at the apex was associated with a substantial pressure gradient between apex and outfl ow tract. The pressure gradient was sensitive to changes in preload an d correlated strongly with peak early transmitral flow. The significan ce of this gradient for intraventricular flow propagation in the norma l and the diseased heart remains to be determined.