MI redefined; troponin remains gold standard

MI redefined; troponin remains gold standard

by Judith Rusk

Cardiology Today

October 2007

VIENNA, Austria – Just as not every patient with an elevated liver function test has hepatitis B, not every patient with elevated troponin levels has had myocardial infarction.


Using this analogy, a group of experts unveiled the new definition of MI at the European Society of Cardiology Congress 2007 last month. Joseph S. Alpert, MD, special assistant to the dean and a professor of medicine in the department of medicine at University Medical Center, Tucson, Ariz., and co-chair of the universal MI definition committee, said that despite the confusion and consternation troponin measurement can cause, it is still the gold standard to define MI.


“However, the advance of science has created a number of nuances that are reflected in the new document,” said Alpert, also a member of the Coronary Heart Disease section of the Cardiology Today Editorial Board.

First update since 2000

The new definition, which will be simultaneously published this month in the European Heart Journal, Circulation and the Journal of the American College of Cardiology is divided into five types (see chart).

According to the ESC’s pocket guideline on the universal definition, “The term myocardial infarction should be used when there is evidence of myocardial necrosis in a clinical setting consistent with myocardial ischemia.”

Alpert said type 4 is the most controversial addition to the redefinition. It was added in light of data from meta-analysis trials presented at last year’s Congress. Those trials, presented in hotline sessions, demonstrated more late stent thrombosis with drug-eluting stents.

Imaging will help demonstrate whether a patient has prior MI, Alpert said. If the patient has new Q waves or pathological healings, imaging evidence of a region of loss of viable myocardium that is thinned or fails to contract in the absence of a nonischemic cause will help.

Implications

Despite the changes, Alpert said the committee does not expect the reported numbers of MI to change much.

“There were 10% and 30% increases (in MI) following first definition,” he said.

Allan Jaffe, MD, professor of medicine at the Mayo Clinic, said defining reinfarction remains a challenge. “We used CK-MB for so long,” said Jaffe, also a member of the Coronary Heart Disease section of the Cardiology Today Editorial Board. Despite one paper published in 2005 that had a small population, trials validating the criteria for recurrent MI have not been done since 1988.

Another challenge is universal definition of MI in clinical trials. Maarten Simoons, MD, Rotterdam, said researchers should complete a small chart – that will be included in the guidelines – that asks pointed questions in defining MI.

When it comes down to it, Jaffe said, clinicians have to rely on their gut when identifying MI.

“There is still a need for good bedside clinical judgment,” he said.


For more information:


Alpert JS, Jaffe A, Underwood SR, Wallentin LC, Simoons ML. Universal definition of myocardial infarction. Symposium #2466-2470. Presented at: European Society of Cardiology Congress 2007; Sept. 1-5, 2007; Vienna, Austria.