In the described case of heart failure, which BNP level supports the diagnosis of heart failure with reduced ejection fraction?

• A. BNP 550 pg/mL
• B. BNP 50 pg/mL
• C. Troponin I 0.02 ng/mL
• D. CRP 2 mg/L

Answer: (B)

BNP is released by the heart’s ventricles when they’re stretched and under increased pressure. In heart failure, especially with reduced ejection fraction, the ventricles face higher filling pressures and wall stress, so BNP levels rise. A markedly elevated BNP reflects this ongoing myocardial strain and supports the diagnosis of heart failure with reduced EF. For example, a level around 550 pg/mL fits HF with reduced EF, whereas a value like 50 pg/mL is unlikely to indicate HF as the primary cause of symptoms. Troponin I and CRP are not natriuretic peptides and don’t specifically diagnose HF—troponin flags myocardial injury and CRP signals inflammation. So the key idea is that substantial BNP elevation aligns with heart failure and reduced EF.