ECHOCARDIOGRAPHIC DETERMINATION OF LEFT-VENTRICULAR PRELOAD, AFTERLOAD, AND CONTRACTILITY DURING AND AFTER EXERCISE

Left ventricular (LV) performance increases during acute exercise, but the mechanisms for this increase are not known. To determine the feas ibility of studying echocardiographic indexes of performance and its d eterminants (preload, afterload, and contractility) during exercise, a nd to examine changes in these indexes, we tested 24 normal male subje cts (aged 21 +/- 5 years) by echocardiography-at rest; at 25%, 50%, 75 %, and 100% maximal oxygen consumption; and immediately, 3 minutes, an d 5 minutes after cycle ergometry. The LV performance (shortening frac tion), preload (LV end-diastolic dimension), afterload (wall stress), contractility, heart rate, and peak systolic blood pressure were measu red. Data could be obtained during 98% of the exercise studies. The LV performance, heart rate, blood pressure, and contractility increased significantly with increasing exercise, reaching peak levels at maxima l exercise, and decreased toward resting levels in the post-exercise p eriod. The LV afterload and preload decreased significantly with incre asing exercise intensity, reaching nadir levels at maximal exercise, a nd increased toward resting levels in the post-exercise period. We con clude that echocardiographic measurement of LV performance and its det erminants is feasible during exercise. Performance of the LV increases with increasing exercise intensity because of an associated increase in contractility and decrease in afterload. These data will serve as a basis for comparison with those from other patient populations.