Enhanced inotropic response to dobutamine in strength-trained subjects with left ventricular hypertrophy

To determine whether strength-trained individuals with physiological concen tric left ventricular (LV) hypertrophy exhibit enhanced inotropic responses to catecholamines, we studied 11 bodybuilders, aged 33.0 +/- 2 (SE) yr old , and 10 sedentary healthy subjects, aged 31.3 +/- 2.4 yr old, at baseline and during infusion of incremental doses of dobutamine after atropine. The bodybuilders had larger LV mass, posterior wall and septal wall thicknesses , and wall thickness-to-radius ratio, assessed with two-dimensional echocar diography, than did the sedentary subjects. There was a significant correla tion between LV mass and lean body mass irrespective of training status. Ba seline LV fractional shortening was similar in the two groups. There was a greater inotropic response to dobutamine in the strength-trained individual s, as evidenced by a steeper slope of the fractional shortening-end-systoli c wall stress relationship with a higher y-axis, intercept and by a shallow er end-systolic wall stress-end systolic diameter relationship without chan ges in end-diastolic diameter. The heart rate response to dobutamine was at tenuated in the strength-trained athletes. There Mras a significant correla tion (r = 0.604, P < 0.05) between the inotropic sensitivity to dobutamine and LV mass normalized for lean body mass in the bodybuilders. The data sug gest that concentric physiological hypertrophy in the resistance-trained in dividuals is associated with enhanced inotropic but not chronotropic respon ses to catecholamines.