Biomarkers of cardiac injury: an update.

Conventional and promising new markers of myocardial injury have become an important diagnostic tool and their prognostic significance is also recognized. In addition, they help identify patients who will derive the most benefit from therapeutic interventions. The literature was searched from the websites of the National Library of Medicine (http://www.ncbi.nlm.nih.gov/) and PubMed Central, the U.S. National Library of Medicine's digital archive of life sciences journal literature (http://www.pubmedcentral.nih.gov/). The data were accessed from books and journals that published relevant articles in this field. The diagnosis of acute myocardial infarction (AMI) has traditionally relied on the combination of chest pain, ECG features, and elevation in serum markers. However, chest symptoms are frequently atypical or absent and ECG changes may be nonspecific or absent. Hence, the diagnosis of acute coronary syndromes has become increasingly dependent on serum markers of cardiac injury. Among them, creatine kinase (CK) is an effective and widely used test, with the recent CKMB assay offering greater specificity and sensitivity. Cardiac troponins facilitate early and rapid diagnosis, enable effective risk stratification in patients with AMI (with or without traditional criteria for MI), and identify those who will benefit from aggressive medical or surgical intervention. Recent data suggest the potential of myoglobin and CKMB isoforms as sensitive markers in the early hours after symptom onset. Cardiac-specific troponins help in rapid diagnosis, prognostication, and treatment of AMI. Troponins also facilitate early detection of recent infarction owing to their prolonged diagnostic window and also aid in the detection of "microinfarction.'' CKMB is used to detect reinfarction or infarct extension, if levels rise again after declining. Finally, novel biochemical markers are receiving attention in ongoing trials. They may prove to be more effective in diagnosis and prognosis than their existing counterparts.