A. Electrocardiogram
Despite the advent of expensive and sophisticated cardiologic tests, the ECG remains the most reliable tool for the confirmation of acute myocardial infarction. The ECG — not the blood cardiac enzymes (CK–MB and troponin), echocardiogram, cardiac nuclear scans — dictates the rapid administration of lifesaving thrombolytic therapy or angioplasty with intracoronary stent.
Two major types of acute infarctions are recognized from the ECG tracing: ST segment elevation myocardial infarction (see Figs. 4 and 5) and non-ST segment elevation myocardial infarction (formerly called non-Q-wave myocardial infarction; see Fig. 6; also see the figures in the chapter entitled Electrocardiography). These diagnoses have replaced the old terminology, transmural and nontransmural myocardial infarction. Today a new term, acute coronary syndrome, has been used to identify patients with acute chest pain who may have ST segment elevation infarction or non-ST segment elevation infarc¬tion. Patients without biochemical markers, CK-MB, or troponins are regarded as having unstable angina. Figure 5 illustrates the current system using acute coronary syndrome. This new terminology is somewhat redundant. It appears that physicians bask in the formulation of new syndromes sometimes with unneeded terminology. To retain the term ST elevation myocardial infarction (MI) would be simple. The diagnosis is easily made and therapy for this condition has been well-defined since the 1980s. It could also be simple in patients with acute chest pain to use the term non-ST elevation if there is ST segment depression with positive cardiac enzymes MI. Both terms became ingrained during the late eighties. Patients with negative troponins are labeled unstable angina. In Fig. 7 the words acute coronary syndrome are synonymous with ‘‘cardiac-like chest pain’’ and can be eliminated from the algorithm. Nonetheless, the term acute coronary syndrome is here to stay and is likely to be used in many countries. There is no test to rival the ECG in the diagnosis of arrhythmias, which are a common clinical cardiologic problem and a common finding in patients with acute myocardial infarction. Arrhythmias occurring during the first few hours of infarction may be life-threatening.

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