Relationship of Left Ventricular Structure

Previous investigators using clinical, hemodynamic, or exercise parameters to predict maximal exercise heart rate (HRmax) have demonstrated age to be the major determinant. Regression coefficients have ranged from -0.3 to -0.6, leaving approximately two thirds of the variance in HRmax unexplained. Because cardiac size and function are directly related to stroke volume and should influence HRmax, we studied 114 male subjects (aged 19 to 73 years) with two-dimensional and M-mode echocardiography who underwent maximal treadmill testing with respiratory gas analysis. Seventy-three were normotensive (diastolic BP<95 mm Hg) and 41 were hypertensive. As in previous studies, HRmax was inversely related to age (HRmax=199-0.63 [age], r= -0.47, p<0.001). M-mode left ventricular (LV) diastolic dimension (LVD) added significantly to the explanation of the variance in HRmax (r=-0.57, p<0.001) (HRmax=236-0.72 [age]-6.8 [LVD]). Thus, the larger the heart, the lower the HRmax. No other echocardiographic measurement or derived parameter added significantly to the explanation of the variance in HRmax. To evaluate the effects of hypertension on HRmax, we studied hypertensives and normotensives separately. Only age was significantly related to HRmax in the normotensives (r=-0.50, p<0.001). In the hypertensive subjects, however, both age and relative wall thickness (RWT) (which describes LV wall thickness in relation to