Diagnosis of myocardial injury by biochemical markers: problems and promises

The role of biochemical markers in the diagnosis of acute coronary syndromes has increased considerably in the past decade. The World Health Organization previously defined acute myocardial infarction as a combination of at least 2 of 3 components: symptoms consistent with acute myocardial infarction, electrocardiogram changes diagnostic of acute myocardial infarction, and an enzyme pattern with classic rise and fall. Measurement of creatine kinase and its MB fraction by various assays was the gold standard for the diagnosis. Troponins are more specific and sensitive markers for myocardial injury, and their increasing utilization has resulted in a broadening of the definition of acute myocardial infarction to incorporate high-risk acute coronary syndromes. Previously, traditional enzyme evaluation left patients with small amounts of cellular death undiagnosed; these patients were categorized as having unstable angina or, worse, noncardiac chest pain. Newer markers now identify these patients as a subgroup at high risk for cardiac death or cardiac events. Newer therapeutic interventions and a more invasive strategy have been shown to improve outcomes in this high-risk subgroup. Increased specificity has also reduced the number of patients who undergo extensive, expensive, and invasive evaluations for noncardiac syndromes due to false elevations of traditional markers. This article comprehensively reviews the evolution of biochemical markers for the diagnosis of acute myocardial infarction, addressing their promise for improving delivery of care and outcomes and their technical and diagnostic pitfalls.

The increasing incidence of coronary artery disease and cardiovascular risk factors among a Southwest Native American tribe: the White Mountain Apache Heart Study

BACKGROUND

Rates of cardiovascular disease and its risk factors seem to be increasing in American Indian populations, yet these changes have received little documentation.

OBJECTIVES

To evaluate incidence rates of coronary artery disease, acute myocardial infarction, and cardiac events during a 10-year period (1987-1996); to assess cardiac risk factors for an American Indian tribe in Arizona.

METHODS

A retrospective medical chart review was performed for tribal members from January 1, 1987-December 31, 1996. Patient records with even minor indications of coronary disease were reviewed independently by 2 cardiologists of the Native American Cardiology Program. Multiple databases were reviewed in an effort to find all diagnoses, and incidence rates were calculated and analyzed for increasing trends. Cardiac risk factors were assessed in a population convenience sample.

RESULTS

From 1987 through 1996, the number of incident cases increased from 3 to 18 for coronary artery disease, 1 to 10 for acute myocardial infarction, and 3 to 26 for cardiac events. Statistically significant increasing trends were calculated for each. Of our youthful convenience sample, 49% had 2 or more cardiac risk factors.

CONCLUSIONS

This study confirms increasing rates of coronary artery disease and its comorbidities in this American Indian population and demonstrates high prevalence of cardiovascular risk factors among tribal members without extant coronary disease. This suggests that coronary disease will likely continue to increase as this population ages. To prevent such increases, culturally appropriate, aggressive preventive interventions are needed.