Diagnosis of MI – Cardiac Markers and Angiography

Cardiac markers are proteins that are secreted from the injured myocardial cells from their damaged cell membranes into the blood. The enzymes like SGOT and LDH were used till the 1980s for assessing the cardiac injury. Nowadays, the most widely used markers in detection of MI include cardiac troponins T and I; and MB subtype of the enzyme creatine kinase. These markers are more specific for indicating the myocardial injury. In fact, the cardiac troponins T and I are released within 4–6 hours of post MI and its level remains elevated for up to 2 weeks. These markers have complete tissue specificity and are ideal markers for assessing the myocardial damage.

Another marker for detecting myocardial injury is Heart-type fatty acid binding protein that is used in some home test kits. The elevated levels of troponins in the chest pain also predict a high probability of future myocardial infarction. Some other new markers include glycogen phosphorylase isoenzyme BB. The diagnosis of myocardial infarction should satisfy two out of three criteria including history, ECG, and enzymes. Following the damage to the heart, the levels of cardiac markers rises over time and because of that reason the blood tests for these markers are taken over a 24-hour interval. As the levels of enzyme take time for rise after a heart attack, patients with chest pain are treated with the assumption of myocardial infarction and evaluation is done for a more concrete diagnosis.

Angiography – The coronary angiography is performed in situations where intervention for restoring blood flow is required. The process includes the insertion of a catheter into the femoral artery and it is pushed to the blood vessels supplying the heart. Now, a radio-opaque dye is administered via the catheter followed by a sequence of x-rays (fluoroscopy). The obstructed or narrowed arteries are identified, and angioplasty is used  as a therapeutic measure. Angioplasty needs extensive skill, and it is performed by a physician who is trained in interventional cardiology.

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