New markers get to the heart of MI screening, diagnosis

Troponin, a new defining marker for a heart attack, has made it to prime time while C-reactive protein waits in the wings.

By Victoria Stagg Elliott, amednews staff. Aug. 20, 2001.

The 59-year-old man went to the emergency department in November 2000 with chest pains and a history of numerous heart attacks. Several hours later, he was diagnosed with a mild heart attack. This diagnosis occurred because, although several traditional cardiac markers were normal, his levels of troponin were elevated.

One month earlier, the European Society of Cardiology and the American College of Cardiology had redefined myocardial infarction to include those with serum evidence of this protein released when the heart is damaged, even in the absence of other traditional heart attack markers. Numerous studies had demonstrated that the presence of troponin meant a worse outcome and the need for more aggressive therapy even if more traditional cardiac tests such as the electrocardiogram were normal.

The patient described is Vice President Dick Cheney, said Fred Apple, PhD, medical director of clinical laboratories at the Hennepin County Medical Center in Minnesota.

"[I]f the diagnosis had been based on the old guidelines this would have been called 'unstable angina.' But because troponin was mildly elevated and he presented with ischemic chest pain, it was called a heart attack."

The new definition is expected to identify 20% to 30% more people as having had myocardial infarction rather than less serious heart-related conditions.

Experts say this will mean more people will receive appropriate treatment and outcomes should improve.

"This helps clinicians in several areas," said Allison Kean, MD, a cardiologist with Northwestern Memorial Hospital in Chicago. "It helps in risk stratification, the estimation of infarct size, and detection of cardiac injury in the postoperative stage, which is often confounded because other serum markers are already elevated because of other factors." [...]

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