Effects of submaximal isometric handgrip on left ventricular size and wall motion

Abstract

To evaluate the effects of sustained submaximal isometric handgrip exercise on the left ventricle in patients with previous myocardial infarction, we utilized the noninvasive techniques of radarkymographic video tracking, measurement of the left heart dimension and calculation of systolic time intervals to assess alterations in wall motion and left ventricular size and function during handgrip exercise performed at a tension level of 15 percent of maximal voluntary contraction. In 9 of 12 patients with dyskinesis or asynchrony at rest the mean amplitude and velocity of systolic outward movement increased during handgrip exercise ( P < 0.05), whereas in 11 patients with initially hypokinetic areas mean amplitude and velocity decreased ( P < 0.05); in 3 patients dyskinesis was produced de novo. In all 12 patients both amplitude and velocity decreased in areas of normal wall motion ( P < 0.05); similar changes occurred in 5 normal control subjects. Alterations in systolic time intervals during handgrip exercise were variable, and no consistent patterns were observed in either patients or control subjects. In seven patients whose left heart dimension increased during handgrip exercise, wall motion abnormalities were more severe at rest than in the five patients whose left heart dimension decreased. The five control subjects showed a decrease in left heart dimension during handgrip exercise. We conclude that the normal response to submaximal isometric handgrip exercise at 15 percent of maximal voluntary capacity is a decrease in left ventricular size and a reduction in both the amplitude and velocity of left ventricular wall motion. Furthermore, in patients with previous myocardial infarction sustained isometric handgrip exercise is a useful maneuver for the intensification or induction of left ventricular wall motion abnormalities. By contrast, no consistent alterations in systolic time intervals were observed during handgrip exercise either in normal subjects or in patients with previous myocardial infarction. Thus, systolic time intervals do not appear to be useful for evaluating the left ventricular response to submaximal handgrip exercise in individual patients.