CONTRIBUTION OF LONG AXIS MOTION OF LEFT-VENTRICULAR OUTFLOW TO CALCULATION OF LEFT-VENTRICULAR STROKE VOLUME

Stroke volume can be calculated by using noninvasive Doppler technique s. The products of pulsed Doppler stroke distance of left ventricular outflow and left ventricular outflow area can often be used to calcula te stroke volume. However, left ventricular outflow also moves longitu dinally toward the apex of the ventricle during systole, so that zero velocity flow cannot be detected by the usual pulsed Doppler studies. We evaluated the contribution of these zero velocity flow to the nonin vasive estimation of left ventricular stroke volume in 20 patients wit h left ventricular disease and in 20 age matched healthy controls. Lef t ventricular stroke distance was calculated by summing the Doppler st roke distance and the outflow long axis motion. The percentage of zero velocity flow for total stroke volume was calculated in each group. C ardiac output was also measured by thermo-dilution technique. The perc entage of zero velocity flow for total noninvasive stroke volume in pa tients with left ventricular disease was 2.5+/-1.1 mi (4.0+/-1.5%), si gnificantly lower than in normal subjects, 3.6+/-1.0 mi (5.5+/-1.5%) ( p<0.05). These long axis motions are significantly reduced, especially in left ventricular disease. Amplitudes of the left ventricular outfl ow long axis motion were correlated with Doppler stroke distance in al l (r=0.54, p<0.01). In patients with myocardial infarction, stroke vol ume by thermo-dilution methods and calculated stroke volume showed goo d correlation both only by Doppler stroke distance (y=1.044x+0.547, r= 0.968) and by Doppler and long axis motion (y=0.989x+0.521, r=0.974). Compared with stroke volume measured by thermodilution method, stroke volume calculated only by Doppler stroke distance was underestimated. We thus demonstrated the influence of zero velocity flow on left ventr icular outflow both in patients with left ventricular disease and in n ormal subjects.