Myocardial Infarctional Redefined

Myocardial Infarctional RedefinedA long-awaited universal definition of myocardial infarction (MI) has been released. A global task force with expertise in biomarkers, electrocardiographic (ECG) criteria, imaging, interventions, clinical trials, and public policy has updated the consensus document from the year 2000. The revised definition is being published simultaneously in European Heart Journal, Journal of American College of Cardiology, and Circulation.

The new definition is important for several reasons. Defining a disease enables clinicians to label patients (make a diagnosis); labeling has implications for patients with respect to their relationships to the medical community and to the rest of society. For example, receiving a diagnosis of MI may change a person’s ability to perform certain jobs.

Unfortunately, clinicians and clinical scientists often define the same disease in different ways.

Characteristics that define a disease in one country might be interpreted differently by physicians in another country. This makes it difficult to compare the results of various studies of patients with a particular disease.
Such is the case with MI. Past attempts to arrive at a standard definition failed, often because of evolving diagnostic technology and confusion surrounding the suggested definition. The first consensus committee recommended that MI be qualified by referring to the amount of heart muscle loss, to the circumstances leading to the infarct, and to the timing of the heart muscle cell death in relation to the time of the observation.

How to label small elevations in blood troponin that occur following percutaneous coronary intervention (PCI) is still controversial. Most delegates favored calling these tiny procedure-related episodes of myocardial injury “true” infarcts because they occurred in the setting of recognizable coronary arterial ischemic interventions.

However, it was felt that these PCI-related events should be distinguished from spontaneous (“wild-type”) MI, which usually presents with the traditional clinical scenario of substernal chest discomfort, accompanied by ischemic electrocardiographic changes and resulting from rupture of an atherosclerotic coronary arterial lesion.

The changes in the definition of an MI have serious consequences for less developed and developing countries. The definition should be used by developed countries immediately and by developing countries as quickly as resources become available.

(Sources: European Society of Cardilogy, American College of Cardiology, American Heart Association, and World Heart Federation, October 19, 2007.)