Which cardiac biomarker may result in a more timely and definitive diagnosis of myocardial injury?

• A. CK-MB
• B. Troponin
• C. Myoglobin
• D. LDH

Answer: (B)

The main idea here is that a biomarker with high cardiac specificity and an early, sustained rise after myocardial injury provides the most timely and definitive diagnosis of myocardial damage. Troponin I or T fits this best because these proteins are unique to cardiac muscle and are released when heart cells are injured. They begin to rise within about 3 to 4 hours after injury, peak around 12 to 24 hours, and remain elevated for several days, allowing reliable detection even if symptoms are delayed or changes are gradual. This combination of early appearance and prolonged elevation, plus high sensitivity and specificity, makes troponin the most definitive indicator of myocardial injury.

CK-MB is more cardiac-specific than non-cardiac markers but can be elevated with skeletal muscle injury and doesn’t provide as reliable a long-lasting signal as troponin. Myoglobin rises very early, but its lack of cardiac specificity means it can be elevated from non-cardiac sources. LDH rises late and nonspecifically, making it less useful for acute diagnosis.