Which test would most likely be used to diagnose heart failure?

The test most commonly used to diagnose heart failure is BNP, or B-type Natriuretic Peptide. This peptide is released by the ventricles of the heart in response to excessive stretching of cardiac myocytes, which occurs when heart failure is present. Elevated levels of BNP in the blood indicate that the heart is under stress and not functioning effectively, making it a key biomarker for diagnosing and assessing heart failure severity.

In this context, other tests listed may assess different aspects of heart health, but they are not specific for diagnosing heart failure. For instance, CK Cardiac measures creatine kinase levels, which can indicate muscle damage but are not specific to heart failure. Carbon Dioxide (CO2) levels provide information about a patient's respiratory function and acid-base balance rather than directly indicating heart trouble. Creatinine levels are commonly assessed to evaluate kidney function and may be affected in heart failure but are not primarily used to diagnose this condition. Thus, BNP stands out as the most relevant test for identifying heart failure.