ESTIMATION OF LEFT-VENTRICULAR CHAMBER AND STROKE VOLUME BY LIMITED M-MODE ECHOCARDIOGRAPHY AND VALIDATION BY 2-DIMENSIONAL AND DOPPLER-ECHOCARDIOGRAPHY

This study has been designed to improve estimation of stroke volume fr om linear left ventricular (LV) dimensions measured by M-mode echocard iography, in symmetrically contracting ventricles. In experimental stu dies, the ratio of LV epicardial long/short axes ''Z'' is about 1.3. W e measured systolic and diastolic epicardial long and short axes by 2- dimensional echocardiography in 115 adults with widely varying LV shor t-axis dimensions (LV end-diastolic dimension = 3.95 to 8.3 cm). In a learning series of 23 normotensive and 27 hypertensive subjects, Z(dia stole) was 1.3 +/- 0.1 and Z(systole) = 1.2 +/- 0.1, similar to findin gs in experimental animals. Regression equations were developed by com paring LV volumes by M-mode and 2-dimensional echocardiography. In a t est series (65 subjects), LV volumes were calculated using separate re gression equations for end-diastolic volume ([LV end-diastolic dimensi on](2) 4.765 - 0.288 x posterior wall thickness]) and for end-systolic volume ([LV end-systolic dimension](2)[4.136 - 0.288 x posterior wall thickness]). Because the term 0.288 x wall thickness was only about 8 % of the first term between brackets, the average wall thickness in th e learning series was substituted in the Z-volume formulas applied to the test series: end-diastolic volume = (4.5 x [LV end-diastolic dimen sions](2)) and end-systolic volume = (3.72 x [LV end-diastolic dimensi on](2)). The mean relative error produced with this simplified method was 0.9% in diastole and 1.4% in systole. Compared with Teichholz' M-m ode volume method, Z-derived end-diastolic volume in the test series w as equally well related to 2-dimensional volumes (both r = 0.88),with a better intercept (1.5 vs -23 ml, p < 0.001) and a slope closer to th e identity line (1.1 vs 1.4). Similar results were found for systolic volumes. In a second test series of 1,721 American Indian participants in the Strong Heart Study without mitral regurgitation or segmental L V wall motion abnormalities, Doppler-derived LV stroke volume (70 +/- 14 ml/beat) was similarly predicted by the Z-derived method (r = 0.65, 70 +/- 11 ml/beat) and Teichholz formulas (r = 0.64, 72 +/- 13 ml/bea t), but Z-derived volumes had a regression line significantly closer t o the identity line (p < 0.005). Thus, LV chamber and stroke volumes c an be determined from M-mode LV diameters over a wide range of LV size s and in epidemiologic as well as clinical populations. The performanc e of this new method appears better than that obtained using the Teich holz formula, with a formula that is easy to handle and makes calculat ion of LV volumes by pocket calculator possible, even from limited ech ocardiographic studies.