Determination of Left Ventricular Preload and Afterload by Quantitative Echocardiography in Man

Abstract

Left ventricular circumferential wall stress at end-diastole (preload) and at the end of isovolumic left ventricular contraction (afterload) was calculated in 48 subjects with chronic myocardial and valvular heart disease by using left ventricular internal dimensions and wall thickness measured by quantitative echocardiography, left ventricular end-diastolic pressure, and aortic end-diastolic pressure. These calculations were then compared with similar determinations made using quantitative angiocardiography. Left ventricular preload and afterload determined by quantitative echocardiography and quantitative angiocardiography correlated significantly (r = 0.978 and 0.864, respectively). Left ventricular preloads of 30 x 10³ dynes/cm² in subjects with mitral stenosis and 39 x 10³ dynes/cm² in subjects with coronary artery disease unassociated with left ventricular dysfunction or mitral regurgitation were close to or within the normal range (32 x 10³ ± 4 x 10³ dynes/cm²). Left ventricular preload in subjects with compensated volume overload was comparable with the angiocardio-graphically calculated values of 63 x 10³, 57 x 10³, and 53 x 10³ dynes/cm² in subjects with coronary artery disease plus mitral regurgitation, mitral regurgitation, and aortic regurgitation, respectively. Left ventricular preload was most elevated in subjects with coronary artery disease associated with segmental left ventricular dyskinesis or akinesis. No significant differences in left ventricular afterload were noted between subject groups, although those with hypertrophic cardiac disease had the lowest calculated values. Quantitative echocardiography is an accurate technique for measuring left ventricular circumferential wall stress (preload and afterload) when left ventricular end-diastolic pressure and aortic end-diastolic pressure can be obtained.