ACUTE MYOCARDIAL INFARCTION 13A
A 71-year-old man presents to the emergency department with a sudden onset of substernal chest pain 1 hour ago. He describes the pain as a heavy pressure sensation that radiates down both arms and is 10 of 10 in intensity. His pain started while he was walking around his yard and improved, but did not resolve, with rest. His medical history is significant for diabetes mellitus. He has smoked 1 pack of cigarettes per day for the past 50 years. His mother died of a myocardial infarction (MI) at age 56 years. On heart examination, you hear an S4 gallop, and on lung examination, you hear bibasilar fine crackles. His electrocardiogram (ECG) shows 3-mm ST-segment elevations in leads II, III, and aVF.
What are the salient features of this patient’s problem? How do you think through his problem?
Salient features: Advanced age; sudden onset of substernal chest pain radiating to the arms; pain worse with exertion; cardiac risk factors of diabetes mellitus, smoking, and family history; S4 gallop and crackles consistent with pulmonary edema; ECG with ST elevations in an inferior distribution
How to think through: Acute coronary syndrome (ACS) includes unstable angina, non–ST elevation MI, and ST elevation MI; all result from myocardial ischemia caused by thrombosis at a site of coronary atherosclerosis. There are other causes of MI, but ACS is the most common. This patient has typical chest pain, meaning substernal, “pressure” or “squeezing,” exertional, and relieved by rest or nitroglycerin. Radiation to the arms correlates strongly with cardiac chest pain. To evaluate a patient with chest pain, first determine the likelihood of ACS as its cause; then stratify the risk for mortality to ensure timely intervention in high-risk patients. Here the history alone strongly suggests ACS. The patient is deemed to be at high risk because of the ST elevations on ECG. If the ECG showed ST depressions, would he still be considered a high-risk patient? (Yes. Evidence of new heart failure confers high risk.) What medications should be administered upon diagnosis? (Aspirin; clopidogrel, heparin, or low-molecular-weight heparin [LMWH]; nitroglycerin; morphine, if needed.) Should he receive a β-blocker? (No. His new heart failure is a relative contraindication.) If the hospital lacks facilities for cardiac catheterization, how should he be managed? (If transfer to another facility for percutaneous coronary intervention [PCI] within 90 minutes of first medical contact is not possible and barring contraindication, fibrinolytic therapy should be given.)
ACUTE MYOCARDIAL INFARCTION 13B
What are the essentials of diagnosis and general considerations regarding acute myocardial infarction?
Essentials of Diagnosis
Sudden development of prolonged (>30 minutes) anterior chest discomfort or pressure
Sometimes masquerading as acute heart failure (HF), syncope, stroke, or shock
ECG: ST-segment elevation or left bundle branch block
Immediate reperfusion treatment is warranted with PCI within 90 minutes (preferred) or thrombolysis within 30 minutes of arrival and within 6 to 12 hours of symptom onset
General Considerations
Results, in most cases, from an occlusive coronary thrombus at the site of a preexisting (although not necessarily severe) atherosclerotic plaque
More rarely, may result from prolonged vasospasm, inadequate myocardial blood flow (e.g., hypotension), or excessive metabolic demand
Very rarely, may be caused by embolic occlusion, vasculitis, aortic root or coronary artery dissection, or aortitis
Cocaine use may cause MI and should be considered in young individuals without risk factors
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