A patient with advanced heart failure exhibits chronically elevated end-diastolic volume. What mechanism most directly diminishes cardiac output under these conditions?

💡 Explanation

Elevated end-diastolic volume leads to over-stretching of cardiac muscle fibers, triggering the Frank-Starling mechanism to a point where further stretching reduces contractile force, because there's reduced myofilament calcium sensitivity. Therefore, cardiac output falls; rather than sympathetic activity increasing it.

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