Review Question - QID 109959

This patient with chest pain and ST-segment elevations in inferior and anterior leads most likely has an inferior wall myocardial infarction with right-sided involvement. Nitroglycerin is contraindicated in these patients.

Nitroglycerin is a nitrate that can be administered sublingually for relief of angina and myocardial infarctions. It works by producing nitric oxide that can diffuse to vascular endothelial and smooth muscle cells. There, the nitric oxide is responsible for stimulating a soluble guanylate cyclase in order to produce increased levels of cyclic GMP. A cGMP-dependent protein kinase then acts to decrease intracellular levels of calcium and results in smooth muscle relaxation. Importantly, nitroglycerin should not be administered in acute myocardial infarcts with inferior wall or right-sided involvement due to a high risk of subsequent hypotension.

Figure A shows ST elevations in the inferior (II, III, and aVF) and anterior precordial (V1 and V2) leads consistent with an inferior wall myocardial infarction with right-sided involvement.

Incorrect Answers:
Answer 1: Binding to metalloproteins such as hemoglobin is characteristic of the behavior of oxygen, which is given during all types of myocardial infarctions.

Answer 2: Inhibition of mevalonate production describes statins, which work by competitively inhibiting HMG-CoA reductase. Statins are indicated for myocardial infarction to help reduce cholesterol levels.

Answer 3: Irreversible inhibition of cyclooxygenase is characteristic of aspirin, which is administered in all types of myocardial infarctions.

Answer 4: Inhibition of pulmonary convertases is characteristic of angiotensin-converting-enzyme inhibitors, which are not contraindicated in acute myocardial infarctions.

Bullet Summary:
Nitroglycerin administration is contraindicated in acute myocardial infarctions with right-sided or inferior wall involvement.