Which condition is a classic cause of high-output heart failure?

• A. Myocardial ischemia
• B. Complete heart block
• C. Aortic stenosis
• D. Thyrotoxicosis

Answer: (D)

High-output heart failure happens when the heart is pumping a very high cardiac output to meet increased circulatory demands, but the body’s tissues still aren’t getting enough perfusion because of the overwhelming metabolic or vasodilatory state. Thyrotoxicosis fits this scenario well. Excess thyroid hormone ramps up the metabolic rate and tissue oxygen use, while also increasing beta-adrenergic sensitivity, which drives tachycardia and stronger heart contractions. Systemic vasodilation lowers afterload, so the heart works harder to maintain perfusion, further boosting cardiac output. Over time, this sustained high output can fatigue the heart and lead to heart failure.

Other conditions listed don’t produce this high-output pattern. Myocardial ischemia impairs contractility, typically causing reduced cardiac output. Complete heart block slows the heart, again lowering output. Aortic stenosis increases afterload, making the heart work harder to eject blood but usually leading to reduced forward output rather than a high-output state.