Blood tests for cardiac problems measure muscle enzymes and other substances released into the blood when there is heart damage. Increased levels of the cardiac biomarkers diagnose and monitor the course of heart attacks and heart failure. Doctors need to know the difference between heart attack and angina, heart failure or other conditions because the treatments and monitoring requirements are different.
CPK
Creatine phosphokinase levels, also known as total CK and CPK, rise when damage to the heart or another muscle occurs. Doctors order the test as part of a cardiac panel when a patient complains of chest or muscle pain. CPK is not specific to heart muscle, but it is one of the first indicators that muscle damage is present. Doctors order CPK levels every four hours after the initial test to monitor muscle damage.
CKMB
Creatine kinase-MB, an isoenzyme closely related to CPK, rises and falls during a heart attack. The CKMB test helps to determine if the muscle damage relates to the heart. Increased CKMB levels rise about three to four hours after the beginning of chest pain. The blood test can also be used to determine if a clot-busting drug is working. CKMB rises and falls faster after a clot-busting drug does its job. Measurements of CKMB reach peak levels after 18 to 24 hours, and then taper off in 72 hours.
Troponin I
Troponin I ordered as a cardiac specific blood test, when elevated, is diagnostic of a heart attack. The troponin test measures the extent of heart muscle damage by the amount of elevation. Troponin T and troponin I are common names for the test. The CPK, CKMB and troponin I are the three tests combined for a cardiac panel. Cardiac panels produce a diagnostic graph that detects heart problems.
BNP
A B-type natriuretic peptide (BNP) test diagnoses and grades the severity of heart failure. The BNP differentiates between heart failure and lung failure. The BNP is elevated during an onset of heart problems related to shortness of breath and congestive heart failure as opposed to enzymes released from heart muscle damage. The BNP is not usually part of the cardiac panel of tests for a myocardial infarction, but it is specific for heart insufficiency, which makes it a valuable tool for monitoring congestive heart problems.
