An endurance athlete's cardiac output increases substantially during exercise. What distinguishes the mechanism enabling this increased output from the response in someone with advanced heart failure?

💡 Explanation

The Frank-Starling mechanism allows the heart to increase its stroke volume (and thus cardiac output) in response to increased venous return and preload, because the heart failure patient's ventricles have reduced compliance and impaired contractility; therefore, their output increase is limited, rather than augmented, by this mechanism.

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