The Electrocardiogram in Coronary Artery Disease

Abstract

The fi rst human electrocardiogram (ECG) was performed by AD Waller in 1887. Willem Einthoven was the fi rst one to use the term ECG in 1901 and named the waves P, Q, R, S and T. The ECG remains a major non-invasive cardiac imaging tool. In the last 30 years newer and more direct imaging modalities, such as echocardiography, nuclear scanning, cardiac computerized tomography (CT) and magnetic resonance imaging (MRI) have been developed, adding to the information gained from the ECG in the assessment of the heart in various stable conditions. Yet, due to its wide availability, low-cost and rapid interpretation, the ECG remains the most commonly used and, perhaps most important of available cardiovascular diagnostic tools; especially for rapid assessment of patients with symptoms compatible with acute coronary syndromes (ACS) and/or arrhythmia. The Electrocardiogram in Coronary AbstractThe electrocardiogram (ECG) remains the most commonly used and, perhaps most important of available cardiovascular diagnostic tools; especially for rapid assessment of patients with symptoms compatible with acute coronary syndromes (ACS) and/or arrhythmia. ST elevation is thought to represent transmural ischemia due to thrombotic occlusion of an epicardial artery. Emergent reperfusion therapy by primary percutaneous intervention (PCI) or thrombolytic therapy is usually indicated. In contrast, patients without ST segment elevation are treated conservatively in the initial stages. However, the distinction between ST elevation myocardial infarction (STEMI) and non ST elevation ACS (NSTE-ACS) is not always clear. Many patients with compatible symptoms have ST elevation not due to "transmural ischemia". On the other hand, occasionally, patients may have acute ischemia due to complete occlusion of an epicardial artery, but their ECG may show minor degree of ST elevation. Moreover, certain distinct ECG patterns have been described in patients presenting without ST elevation that are associated with higher risk. Recognition of these specifi c patterns of NSTE-ACS, as well as common patterns suggesting non-ischemic ST elevation is crucial.