Echocardiographie Determination of Stroke Volume and Ejection Fraction during Exercise: Analysis from Left Ventricular External Dimension

Abstract

To examine the role of left ventricular (LV) wall thickening in the increase of ejection fraction during supine ergometer exercise, M-mode echocardiography was used to assess LV diameters and performance during staged ergometer exercise. Ergometer exercise was done in 15 healthy subjects (mean age of 25 years) using a cycle ergometer by 25 W/min increments every 3 min to exhaustion with measuring systolic blood pressure. Exercise was stopped at a mean time of 14 min. Ejection fraction significantly increased from 0.64 at rest to 0.78 at peak exercise as the stages went up. Wall thickness of the LY posterior wall (PW) and ventricular septal wall (VS) at end-systole increased significantly from 13 mm (PW) and 12 mm (VS) at rest to 16 mm (PW) and 15 mm (VS) at peak exercise. LV internal dimension (LVID) in end-systole decreased significantly from 30 mm at rest to 24 mm at peak exercise as the stages went up. LVID at end-diastole did not change from 47 mm at rest during light exercise, and slightly decreased to 46 mm at peak exercise. There was no change in LV external dimension either at end-systole or at end-diastole during any stage of exercise. Decreases in end-systolic and end-diastolic LVID during exercise resulted only from the increase in LV wall thickening. In conclusion, the increase in ejection fraction during supine ergometer exercise results mainly from an increase in end-systolic wall thickness, not from Frank-Starling effect in normal subjects.