A. Diagnosis
Non-ST segment elevation MI (non-Q-wave MI) is treated differently from acute myocardial infarction in which the ECG shows elevation of the STsegment (see Figs. 2 and 3). The diagnosis is made from the ECG pattern, and the presence of elevated cardiac enzymes, particularly elevated troponins, assessed in blood samples taken on admission to the emergency room and 6 and 12 h later. The troponins are a more sensitive marker of cardiac necrosis than the CK–MB enzymes. Troponin testing represents a major advance in detecting micro-infarctions that may be missed by CK–MB.
The diagnostic ECG features include ST segment depression greater than 0.5 mm (in Europe it is greater than 0.1 mV, see Fig. 4).
B. Management
Figure 8 gives an algorithm depicting the management of non-ST segment elevation MI.
1. Beta-Blockers
A beta-blocking drug and intravenous nitroglycerin are administered to relieve pain and cause cardiac stabilization.
2. Platelet IIb/IIIa Receptor Blocker
Beta blockers are recommended for high-risk patients. Abciximab has proven beneficial after angiography in patients selected for immediate PCI. This drug has no role outside this indication. It proved more beneficial than tirofiban in clinical trials. Eptifibatide and tirofiban are approved for PCI and for use during the wait before angiography. High-risk patients are most vulnerable during the first 48 h after admission awaiting PCI. Diabetic patients benefit the most from platelet receptor blocker therapy and benefit is maximal in diabetic patients when abciximab is used for PCI.

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