A 47-year-old woman is evaluated for exertional dyspnea. The patient is a smoker with type 2 diabetes mellitus, mild normocytic anemia, and stage 3 chronic renal disease. Her family history is insignificant. Blood pressure is 142/88 mm Hg and pulse is 76/min. BMI is 32 kg/m². Single photon emission CT images of the heart are obtained at rest and after 5 minutes of treadmill exercise by using separate intravenous injections of technetium-99-labeled perfusion agent, as seen below, with the bottom panel showing images of the heart at rest (REST), and the top panel showing images of the heart after exercising (STRESS). This patient would benefit most from which of the following medications?

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Explanation: 11ec25c8_d346_76ee_bc81_c169059305e4_MD0003_00 Technetium-99-labeled (Tc-99m) perfusion agents (sestamibi or tetrofosmin) have a half-life of 6 hours, passively diffuse into perfused myocardial cells, have minimal redistribution afterward, and can provide an assessment of both myocardial function and perfusion. Tc-99m is injected at rest and images are obtained during the gated single photon emission CT (SPECT) scan (bottom panel above; REST). The patient then undergoes stress testing (physiologic or pharmacologic) and has repeat gated SPECT images (top panel above; STRESS). Any differences between rest and stress images can help identify ischemia. Patients with normal tracer uptake at both rest and exercise have a low likelihood of ischemia with an excellent prognosis and <1% annual risk of coronary artery disease (CAD). A decreased tracer uptake both at rest and with exercise (fixed defect) indicates likely scar tissue with decreased perfusion and CAD. A decreased tracer uptake with stress but normal uptake at rest (reversible defect) indicates inducible ischemia and likely CAD. This is seen in this patient's apical images (arrows in top panel). Current guidelines recommend antiplatelet therapy (eg, aspirin) for prevention of myocardial infarction, beta blockers, and modification of the patient's risk factors (eg, smoking cessation, lipids, diabetes). (Choice A) Albuterol is a beta agonist that may cause tachycardia, elevated blood pressure, and possible arrhythmias in a patient with suspected CAD. Current guidelines recommend beta blockers to reduce the potential for future coronary events. (Choice C) Appetite suppressants are sympathomimetics that can cause significant elevations in heart rate and blood pressure and are contraindicated in patients with CAD. (Choice D) Erythropoietin stimulates erythropoiesis for this patient's anemia but can cause serious cardiovascular events, thromboembolic events, stroke, and increased mortality in patients with cardiovascular disease. (Choice E) Metformin may cause lactic acidosis when given to patients with conditions predisposing to hypoxia (eg, cardiovascular disease, chronic kidney disease) and should be avoided in this patient. Educational objective: Single photon emission CT scan is a useful tool to evaluate for coronary artery disease and indicates inducible ischemia when a reversible defect is noted on stress and rest images. Antiplatelet therapy is the preferred treatment to prevent coronary artery disease in these patients. References: SPECT imaging for detecting coronary artery disease and determining prognosis by noninvasive assessment of myocardial perfusion and myocardial viability. (http://www.ncbi.nlm.nih.gov/pubmed/21732226)

A 47-Year-Old Woman Is Evaluated for Exertional Dyspnea