Blog | Monday, January 7, 2013

When hearts attack: changing the definition of myocardial infarction

How does a doctor diagnose your collection of symptoms as a heart attack (it shouldn't happen to you)? The answer used to be:
--by a combination of biomarkers (the results of tests that measure the level of molecules, such as troponin, which are a result of damage to the heart muscle),
--changes in the electrocardiogram (the heart's electrical map), and
--the clinical characteristics of the story someone tells about their chest pain, or their shortness of breath, and what secrets they give up on physical examination.

This combination was susceptible to clinical judgment. Someone could present with typical signs in one, two, or three categories and still be classified as having a heart attack.

Here comes the American College of Cardiology in October and publishes a new set of criteria that focus on the definition of infarction as any tissue damage in the heart due to ischemia (lack of blood flow). Not all causes of infarction are the same, of course; acute damage is different from chronic ischemia, which in turn is different from damage to the heart muscle owing to other causes.

But a basic threshold, I can't help thinking, has been crossed. The heart attack, the sudden death of heart tissue, has been nuanced and ever so subtly cast aside in favor of a basic physiological-biochemical understanding of cardiac physiology.

I am pretty sure this is all to the good. If causes of cardiac muscle damage can be distinguished, then we should we able to figure out which tests and treatments are appropriate for these different causes. Not every instance of cardiac damage is a heart attack.

But, as always when new knowledge is hammered out, the old definitions stay behind. There is a simplicity to the "heart attack." We need to convey the subtlety of these cardiological definitions while retaining the lifesaving urgency of the old notions.

Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews. He is also a poet, journalist and translator in Yiddish and English. This post originally appeared at his blog.