In congestive heart failure, how does the Frank-Starling relationship change?

• A. It directly reduces systemic vascular resistance
• B. The Frank-Starling relation is blunted due to reduced contractility in heart failure
• C. It has no effect on stroke volume
• D. It causes a proportional increase in stroke volume in all cases

Answer: (B)

The main idea is how the heart’s ability to convert filling into pumping power changes when failure occurs. The Frank-Starling mechanism says that, in a healthy heart, filling more (increasing end-diastolic length of the muscle fibers) leads to a stronger contraction and a larger stroke volume. But in congestive heart failure the heart’s contractile strength is reduced. That weakened myocardium can’t translate extra preload into as much stronger contraction, so the relationship between preload and stroke volume becomes blunted. The stroke volume rises less for any given increase in filling, and the curve sits lower than normal. This diminished responsiveness helps explain why patients with heart failure can have high filling pressures but still have reduced forward cardiac output, contributing to symptoms of congestion.

Other statements don’t fit because the change is not about directly lowering systemic vascular resistance, and the relationship does affect stroke volume. It’s not a universal, proportional increase in stroke volume in all cases in heart failure, since the damaged contractility limits the heart’s response to increased preload.