[Influence of preload alteration on the transmitral flow velocity in patients with old myocardial infarction: effects of nitroglycerin and lower body negative pressure]

We studied the influence of preload alteration on the pattern of transmitral flow as obtained by pulsed Doppler echocardiography. In protocol I, 14 patients with old myocardial infarction (OMI) were observed by simultaneous measurements of transmitral flow by PDE and left ventricular end-diastolic dimension (LVDd) using M-mode echocardiography during the control period and after sublingual nitroglycerin. In protocol II, eight patients with OMI were similarly observed during stepwise lower body negative pressure (LBNP: 0, -10 and -20 mmHg). The rapid filling phase was categorized in two subphases at peak R as the first half and second half phases. The integrals of each half phase and the atrial systolic phases (IR1, IR2 and IA) were measured by planimetry. After the administration of nitroglycerin, LVDd decreased significantly; whereas the mean arterial pressure decreased and heart rate increased significantly. The peak R and IR1 decreased significantly, but the peak A, IR2 and IA remained unchanged. During LBNP, LVDd decreased stepwise; whereas there was no change in the mean arterial pressure or heart rate. The changes in the peak R and IR1 paralleled the preload reduction during LBNP. The peak A, IR2, and IA remained unchanged. In conclusion, the first and second half volumes during the LV rapid filling phase can be influenced by various factors. The patterns of the transmitral flow velocity, the maximal velocity and first half volume in the LV rapid filling phase may be influenced by preload alteration.