Oxygen pulse during exercise is related to resting systolic and diastolic left ventricular function in older persons with mild hypertension

Abstract

The mechanisms responsible for impaired cardiovascular hemodynamics during exercise among persons with milder forms of hypertension are not well documented. We examined the relationship of oxygen pulse during exercise, a correlate of stroke volume, with echocardiographic indices of resting left ventricular function to determine whether abnormal contractility and relaxation are related to abnormal cardiovascular dynamics during exercise among such persons. Subjects were 44 men and 55 women ages 55 to 75 years with mild hypertension but who were otherwise healthy. Resting left ventricular systolic and diastolic functions were assessed with 2-dimensional Doppler echocardiography and tissue Doppler imaging. Oxygen pulse (millimeters per beat) at rest and during multistage treadmill testing was derived from measurements of oxygen consumption and heart rate. The slope of oxygen pulse between successive exercise stages was calculated. After a steep rise in oxygen pulse from rest to stage 1 of exercise, a markedly diminished oxygen pulse slope was seen between subsequent exercise stages. In stepwise regression analysis, the increase in the slope of oxygen pulse from rest to stage 1 was explained by a greater lean body mass (57%, P < .001) and a larger left atrial size (2%, P < .001). After exercise stage 1, the increase in the slope of oxygen pulse was explained by sex (24%, P < .001), higher mitral E/A ratio (6%, P < .001), and higher mitral annular systolic velocity (6%, P < .001). These results suggest that a blunted oxygen pulse response to exercise among older persons with milder forms of hypertension may reflect impaired left ventricular stroke volume changes during exercise secondary to subtle abnormalities in both systolic and diastolic left ventricular functions.