Left atrial phasic function interacts to support left ventricular filling during exercise in healthy athletes

Abstract

We studied the contribution of phasic left atrial (LA) function to left ventricular (LV) filling during exercise. We hypothesized that reduced LV filling time at moderate-intensity exercise limits LA passive emptying and increases LA active emptying. Twenty endurance-trained males (55 ± 6 yr) were studied at rest and during light- (∼100 beats/min) and moderate-intensity (∼130 beats/min) exercise. Two-dimensional and Doppler echocardiography were used to assess phasic volumes and diastolic function. LV end-diastolic volume increased from rest to light exercise (54 ± 6 to 58 ± 5 ml/m(2), P < 0.01) and from light to moderate exercise (58 ± 5 to 62 ± 6 ml/m(2), P < 0.01). LA maximal volume increased from rest to light exercise (26 ± 4 to 30 ± 5 ml/m(2), P < 0.01) related to atrioventricular plane displacement (r = 0.55, P < 0.005), without further change at moderate exercise. LA passive emptying increased at light exercise (9 ± 2 to 13 ± 3 ml/m(2), P < 0.01) and then returned to baseline at moderate exercise, whereas LA active emptying increased appreciably only at moderate exercise (6 ± 2 to 14 ± 3 ml/m(2), P < 0.01). Thus, the total atrial emptying volume did not increase beyond light exercise, and the increase in LV filling at moderate exercise could be attributed primarily to an increase in the conduit flow volume (19 ± 3 to 25 ± 5 ml/m(2), P < 0.01). LA filling increases during exercise in relation to augmented LV longitudinal contraction. Conduit flow increases progressively with exercise in athletes, although this is driven by LV properties rather than intrinsic LA function. The pump function of the LA augments only at moderate exercise due to a reduced diastolic filling time and the Frank-Starling mechanism.

Left atrial function in elite athletes: A meta‐analysis of two‐dimensional speckle tracking echocardiographic studies

“…Conduit LA function represent the ability to passively transfer blood into the LV. The LA active function shows the LA contraction during the last diastolic phase that enables up to 30% of LV stroke volume in athletes …”

Effect of induced chronic atrial fibrillation on exercise performance in Standardbred trotters

“…For horses and humans in sinus rhythm (SR), the active contribution from the atria can account for approximately 10%‐20% of ventricular stroke volume at rest, but the absent atrial pumping function in AF patients rarely clinically affects hemodynamic parameters at rest. However, the atrial pumping function becomes more important as the intensity of exercise increases, because the relative portion of passive filling is decreased because of tachycardia . A marked decrease in cardiac output therefore can be expected in AF patients during exercise and tachycardia …”

“…However, the atrial pumping function becomes more important as the intensity of exercise increases, because the relative portion of passive filling is decreased because of tachycardia. 14 A marked decrease in cardiac output therefore can be expected in AF patients during exercise and tachycardia. 15 Previous studies have reported disproportional tachycardia in AF horses during exercise, 3,16,17 and 1 study also reported a broadening of QRS complexes and abnormal ventricular activation.…”

Influence of Left Atrial Function on Exercise Capacity and Left Ventricular Function in Patients With Heart Failure and Preserved Ejection Fraction

“…This emphasizes the physiological need for an increased early LV filling as an adaptation to exercise. 30 In HFpEF, limited conduit function at rest is likely to exaggerate during exercise and might no longer be compensated for by active LA contraction, impacting on LV early filling, LV stroke volume, cardiac output, and ultimately exercise capacity. …”