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Thursday, March 31, 2011

Acute Inferior ST-elevation Myocardial Infarction

A 64-year-old woman is evaluated in the emergency department 6 hours after the onset of severe crushing chest pain associated with diaphoresis, nausea, and vomiting. Her medical history is significant only for hyperlipidemia; her medications are atorvastatin and aspirin. On physical examination, blood pressure is 140/88 mm Hg, and heart rate is 88/min. The lungs are clear, and no cardiac murmurs are heard. Examination of the abdomen and extremities is normal. Electrocardiogram shows a 3-mV ST elevation in leads II, III, and aVF, with occasional premature ventricular contractions. The hospital does not have cardiac catheterization facilities, and the patient is therefore given fibrinolytic therapy. Her chest pain resolves; she has two episodes of 6- to 10-beat ventricular tachycardia and stable hemodynamic parameters. Electrocardiogram now shows <0.5-mV ST elevation.

In addition to heparin and aspirin, which of the following approaches is the most appropriate next step in the management of this patient?
A Amiodarone
B β-Blocker
C Coronary angiography
D Lidocaine

Key Point
β-Blocker therapy reduces infarct size and the frequency of recurrent myocardial ischemia and improves short- and long-term survival.

Answer and Critique (Correct Answer = B)

This patient has features of successful reperfusion after an acute inferior ST-elevation myocardial infarction and may be treated medically until risk stratification is performed or recurrent ischemia or complications occur. The usual management consists of heparin, aspirin, β-blockers, angiotensin-converting enzyme inhibitors, and statins. Clinical trials show that β-blocker therapy reduces infarct size and the frequency of recurrent myocardial ischemia and improves short- and long-term survival.

Evidence of successful fibrinolysis involves resolution of both chest pain and ST elevation. The rapidity with which these resolve is directly related to early patency of the affected artery. Reperfusion arrhythmias, typically manifested as a transient accelerated idioventricular arrhythmia, usually do not require additional antiarrhythmic therapy with lidocaine or amiodarone.

Immediate coronary angiography is not indicated unless recurrent ischemia, persistent ST elevation, or hemodynamic instability, including heart failure, occurs.

1. Kopecky SL. Effect of beta blockers, particularly carvedilol, on reducing the risk of events after acute myocardial infarction. Am J Cardiol. 2006;98:1115-9. Epub 2006 Aug 31. [PMID: 17027583]

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