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

Objectives. This study evaluated the role of preload reserve in the stroke volume response to exercise in patients with left ventricular systolic 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 the nonaugmentation of stroke volume during exercise. Methods. In 32 patients with left ventricular systolic dysfunction and 16 healthy control subjects, mitral and aortic velocities were recorded by Doppler echocardiography at rest and during submaximal supine bicycle exercise. Stroke volume, peak early (E) and late (A) mitral velocities, A/E ratio and end diastolic filling were measured at rest and during exercise. Results. Stroke volume increased significantly in control subjects but did not change in patients. Peak early mitral velocity increased significantly and to the same extent in both groups, whereas peak late mitral velocity and end-diastolic filling increased significantly in both groups but more so in control subjects; the A/E ratio increased significantly in control subjects but did not change in patients. In addition, stroke volume correlated significantly with peak late mitral velocity during exercise in patients (r = 0.72, p < 0.001). Conclusions. Compared with control subjects, patients with left ventricular systolic dysfunction exhibited limited increases in both stroke volume and late left ventricular filling during exercise. Furthermore, their stroke volume response correlated with the capacity of the left ventricle to increase late diastolic filling, that is, preload reserve.