Which lab value is considered diagnostic for congestive heart failure?

• A. BNP
• B. Angiotensin I
• C. Renin
• D. Troponin-C

Answer: (A)

BNP is released by the heart’s ventricles when they are stretched from volume overload, so its level in the blood reflects the degree of cardiac wall stress seen in congestive heart failure. When a patient presents with breathing difficulty, a higher BNP level supports a diagnosis of heart failure and helps distinguish it from noncardiac causes like lung disease. BNP levels correlate with HF severity and tend to decrease with effective treatment.

Angiotensin I and renin are part of the RAAS system and indicate hormonal activation, but they are not diagnostic markers for heart failure. Troponin-C signals myocardial injury, such as from a heart attack, rather than the volume overload state of heart failure. So BNP best aligns with diagnosing congestive heart failure in this context.