INFLUENCE OF PRELOAD RESERVE ON STROKE VOLUME RESPONSE TO EXERCISE INPATIENTS WITH LEFT-VENTRICULAR SYSTOLIC DYSFUNCTION - A DOPPLER-ECHOCARDIOGRAPHIC STUDY

Objectives. This study evaluated the role of preload reserve in the st roke volume response to exercise in patients with left ventricular sys tolic dysfunction by assessing the relation between stroke volume and late left ventricular diastolic filling during exercise. Background In patients with left ventricular diastolic dysfunction, the absence of left ventricular distension is the fundamental mechanism explaining th e nonaugmentation of stroke volume during exercise. Methods. In 32 pat ients with left ventricular systolic dysfunction and 16 healthy contro l subjects, mitral and aortic velocities were recorded by Doppler echo cardiography at rest and during submaximal supine bicycle exercise. St roke volume, peak early (E) and late (A) mitral velocities, A/E ratio and end diastolic filling were measured at rest and during exercise. R esults. Stroke volume increased significantly in control subjects but did not change in patients. Peak early mitral velocity increased signi ficantly and to the same extent in both groups, whereas peak late mitr al velocity and end-diastolic filling increased significantly in both groups but more so in control subjects; the A/E ratio increased signif icantly in control subjects but did not change in patients. In additio n, stroke volume correlated significantly with peak late mitral veloci ty during exercise in patients (r = 0.72, p < 0.001). Conclusions. Com pared with control subjects, patients with left ventricular systolic d ysfunction exhibited limited increases in both stroke volume and late left ventricular filling during exercise. Furthermore, their stroke vo lume response correlated with the capacity of the left ventricle to in crease late diastolic filling, that is, preload reserve.