A 45-year-old woman comes to the clinic due to occasional episodes of nocturnal substernal chest pain that wake her from sleep. The episodes last 10-15 minutes and resolve spontaneously. She leads a sedentary lifestyle but states that she can climb 2 flights of stairs without discomfort. The patient smokes cigarettes but does not use illicit drugs. Blood pressure is 130/70 mm Hg, pulse is 78/min and regular, and respirations are 13/min. BMI is 28 kg/m². The jugular veins are flat with the patient in a sitting position and there are no carotid bruits. Lungs are clear on auscultation. There are no heart murmurs. ECG shows normal sinus rhythm with no repolarization abnormalities. Extended ambulatory ECG monitoring shows transient ST-segment elevation in leads V4-V6 during a pain episode. The pathophysiologic mechanism of this patient's condition is most similar to that of which of the following?

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11ec25c8_d344_05ea_bc81_bfc2602d3520_MD0003_00 This patient's clinical presentation is consistent with vasospastic angina (formerly known as variant or Prinzmetal angina). Vascular smooth muscle hyperreactivity leads to focal or diffuse spasm of the coronary arteries, transient myocardial ischemia, and resulting angina. Patients typically have recurrent episodes of chest discomfort that occur at rest or during sleep. Cigarette smoking is a known risk factor, but patients are typically young and lack other risk factors for coronary artery disease (eg, hypertension, diabetes). As the vasospasm leads to transmural myocardial ischemia, the diagnosis is typically made by ambulatory ECG showing contiguous ST elevation during an episode of chest discomfort. The underlying pathophysiologic mechanism of vasospastic angina is similar to that of Raynaud phenomenon, a disorder characterized by cold- or stress-induced hyperreactivity of the digital arterial smooth muscle, leading to episodic vasospasm in the fingers and toes. Accordingly, calcium channel blockers are an effective first-line pharmacologic therapy for both Raynaud phenomenon and vasospastic angina. However, despite the underlying pathophysiologic similarities, an increased prevalence of Raynaud phenomenon in patients with vasospastic angina (or vice versa) has not been clearly established. (Choice A) Intermittent claudication refers to muscle cramps due to exertion-induced ischemia that typically occurs in the lower extremities in the setting of atherosclerotic peripheral artery disease. This mechanism is similar to typical angina (due to coronary artery disease); however, vasospasm, rather than atherosclerotic arterial narrowing, is the major mechanism of vasospastic angina. (Choice B) Lacunar strokes are due to occlusion of small, penetrating arteries supplying the basal ganglia, subcortical white matter, and pons. They typically result from chronic vasculopathy with lipohyalinosis and microatheroma formation in patients with hypertension and diabetes mellitus. Vasospasm does not play a role. (Choice C) The most common cause of pulmonary embolism is embolization of thrombus from the deep veins of the lower extremities. Vasoactive angina does not involve thromboembolic phenomena. (Choice E) Takayasu arteritis is a chronic vasculitis that affects the aorta and major arterial branches of the aorta. The pathogenesis is related to cell-mediated inflammation rather than vasospasm. Educational objective: Vasospastic angina is characterized by recurrent chest discomfort resulting from hyperreactivity of vascular smooth muscle, leading to intermittent coronary artery vasospasm. Raynaud phenomenon mainly affects the digital arteries and occurs through a similar mechanism. References: International standardization of diagnostic criteria for vasospastic angina. (http://www.ncbi.nlm.nih.gov/pubmed/26245334) Clinical practice. Raynaud's Phenomenon. (http://www.ncbi.nlm.nih.gov/pubmed/12324557) A vascular mechanistic approach to understanding Raynaud phenomenon. (http://www.ncbi.nlm.nih.gov/pubmed/25536485)

A 45-Year-Old Woman Comes to the Clinic Due to Occasional