Abstract
The effect of a passive change from supine to 25-degree head-up tilted position on left ventricular volume was studied by echocardiography and other noninvasive techniques in 18 normal subjects, 6 patients with compensated LV volume overloading, and 12 patients with LV failure. In normal subjects and patients with compensated LV volume overloading, 10 minutes of head-up tilt resulted in a significant decrease in the echocardiographic LV internal dimension equivalent to a decrease in the calculated LV end-diastolic volume of 27 and 16 per cent, respectively. In contrast, no change in LV end-diastolic dimension and volume was noted during tilt in the patients with LV failure. The response of heart rate, blood pressure, and LV ejection fraction to this intervention was insignificant in all groups. These data indicate that volume preload is unresponsive to postural changes in patients with LV failure but not in normal subjects or in those with compensated LV volume overloading. It is suggested that the effect of posture on LV volume and output is primarily determined by the absence or presence of LV failure and the consequences of it on the peripheral circulation.