Which cardiac marker is primarily used to monitor for myocardial infarction?

Troponin I is the primary cardiac marker used to monitor for myocardial infarction. This protein is released into the bloodstream when there is damage to the heart muscle, which occurs during an infarction. Troponin I is highly sensitive and specific for myocardial injury, making it a reliable indicator for diagnosing and assessing the severity of acute coronary syndromes, particularly myocardial infarction.

The elevation of troponin I levels typically occurs within a few hours after the onset of injury and can remain elevated for several days, allowing for continuous monitoring of cardiac damage. This prolonged window of detection is beneficial for both acute and retrospective diagnoses.

In contrast, while other markers like myoglobin, lactate dehydrogenase, and creatine kinase can indicate cardiac injury, they are not as specific or reliable as troponin I. Myoglobin rises early but is less specific to cardiac muscle, lactate dehydrogenase is a less sensitive marker and its elevation may occur in various conditions not limited to myocardial infarction, and creatine kinase, although it can indicate myocardial damage, has various isoenzymes and its elevation can occur in skeletal muscle injury as well. These factors make troponin I the preferred choice for monitoring myocardial infarction.