Noninvasive evaluation of left ventricular function by echocardiography during lower body negative pressure (LBNP)

Noninvasive methods for simultaneous evaluation of left ventricular (LV) dimensions and performance have a wide potential area of application. In this study standard echocardiographic techniques were used to derive LV function curves in 7 normal men, mean age 28, from LV diameter measurements at rest and after 10 min of LBNP at -40 mm Hg. This level is known to cause a significant decrease in circulating blood volume and ventricular filling pressure. LV end diastolic (LVEDV), end systolic (LVESV), and stroke volumes (SV) were estimated from the cubed diameters and expressed in ml/m² body surface area. Mean data are presented. Repeat studies in 5 subjects demonstrated that the measurements were reproducible with r = 0.96 for LVEDV and r = 0.85 for LVESV. The concurrent decrease in LVEDV and SV during LBNP is consistent with a normal LV function curve. The absence of significant changes in LVESV and heart rate suggests a Starling effect without major changes in contractile state in contrast to the response to e.g. isometric exercise and amyl nitrate inhalation. The unchanged blood pressure also makes SV a valid index of LV performance. The procedure is safe and readily performed under clinical conditions and offers promise as a noninvasive means of assessing LV function.