Left ventricular performance characteristics in trained and sedentary dogs.

Training effects on left ventricular (LV) performance were studied in 14 dogs. Nine had chronically implanted LV pressure transducers, five dogs had sham operations. Ventriculographic evaluation of LV function was performed initially in all animals. The sham-operated dogs were killed. The remaining nine dogs were divided into an exercise group (n - 5) and a sedentary group (n = 4). The exercise group ran on a treadmill for 10 wk with a progressively more rigorous routine. The trained dogs had a decreased heart rate response to graded exercise after 10 wk. At similar heart rates, LV end-diastolic volume (pre: 30.3 +/- 3.0, post: 41.8 +/- 2.4 ml) increased significantly after training (P less than 0.05), but ejection fraction was unchanged (pre: 0.68 +/- 0.03, post: 0.67 +/- 0.06). Stroke work (pre: 1848 +/- 199 X 103, post: 4968 +/- 168 X 103 dyn-cm, P less than 0.05) also increased after training. In the presence of a tachycardia, peak dP/dt and peak contractile element shortening velocity showed increases after training. No significant changes in LV volumes, pump performance, or contractility indices were found in the sedentary group. Chronic endurance training alters the size, and appears to improve pump performance of the LV.