Hemodynamic responses at anaerobic threshold during exercise in preload insufficiency.

Background: Preload insufficiency is an underrecognized cause of exercise intolerance identified during invasive cardiopulmonary exercise testing, and defined hemodynamically by decreased biatrial filling pressures, cardiac output, and oxygen consumption (V̇O₂) at peak effort. Patients with preload insufficiency, however, typically present with symptoms of dyspnea on exertion, and/or exercise intolerance at submaximal efforts, particularly when performing activities of daily living. The cardiopulmonary hemodynamics and physiology at submaximal work levels of preload insufficiency have not been previously investigated. We hypothesized that preload insufficiency hemodynamics exist along a continuum, with submaximal exercise values reflecting peak exercise cardiopulmonary hemodynamics.

Methods: We compared submaximal cardiopulmonary hemodynamics, measured at anaerobic threshold, between preload insufficiency patients and age-matched controls referred for dyspnea but with normal exercise responses.

Results: Our study included 66 patients: 41 with preload insufficiency and 25 controls. Preload insufficiency patients exhibit significantly reduced V̇O₂, watts, and METS at submaximal levels compared to controls, alongside earlier anaerobic threshold achievement and similar heart rates at anaerobic threshold.

Conclusions: These findings underscore the profound impact of preload insufficiency on submaximal exercise capacity, emphasizing the importance of its recognition and management. This insight sets the stage for further investigations into interventions targeting preload insufficiency at submaximal exercise levels to enhance both exercise performance and quality of life.