In normal subjects, exercise decreases left atrial volume and increases its ejection fraction, but the volumetric contribution to left ventricular filling remains static.
Observational
How does exercise affect left atrial physiology and its contribution to cardiac output in normal subjects?
In normal subjects, exercise increases cardiac output primarily through heart rate and conduit flow rather than increased LA reservoir contribution, providing a physiological benchmark for assessing LA pathology.
Diseases of the left atrium (LA) are major sources of disability (e.g., strokes and fatigue), but its exercise physiology has been unstudied. Such knowledge may allow early recognition of disease and suggest therapies. We show that in normal subjects, low-level exercise decreases LA volume and increases its ejection fraction. However, these changes offset each other volumetrically, and the contribution to LV filling from a full to an empty LA (reservoir function) is static. Higher levels of exercise do not change LA reservoir contribution. Blood flowing directly from the pulmonary vein to LV (conduit flow) impelled by augmented LV active relaxation (suction) is the major source of a modest increase in LV stroke volume. The major source of increased cardiac output with exercise is heart rate. During all stages of exercise, the LA works hard but only to keep up. We believe that our findings provide an additional set of benchmarks through which to quantitate LA pathology and gauge its progression.
Bhatt et al. (Fri,) conducted a observational in Normal subjects. Exercise was evaluated on Left atrial volume, ejection fraction, and contribution to LV filling. In normal subjects, exercise decreases left atrial volume and increases its ejection fraction, but the volumetric contribution to left ventricular filling remains static.