A 52-year-old man with mild asthma presented to the hospital after an episode of unheralded syncope while walking. On arrival, he was afebrile, with a blood pressure of 120/80 mm Hg, heart rate of 35/min, respiratory rate of 16/min, and pulse oximetry of 98% on ambient air. His examination revealed regular bradycardia without cannon A waves, clear lung fields to auscultation, and warm extremities. Chest radiography revealed hilar adenopathy. Electrocardiography showed sinus bradycardia, first-degree atrioventricular block, left posterior fascicle, and right bundle branch blocks (Figure 1A). Transthoracic echocardiography revealed an ejection fraction of 50% without regional variation. On exercise stress single-photon emission computed tomography, the patient completed 9 minutes of a standard Bruce protocol and developed transient high-grade atrioventricular block but had no ischemic ST-segment changes or defects on perfusion imaging. Cardiac magnetic resonance imaging (cMRI) with gadolinium contrast-enhanced first-pass myocardial perfusion imaging at rest and contrast-enhanced late gadolinium enhancement imaging revealed low-normal left ventricular systolic function but no other abnormalities (Figure 1B).
Wadhera RK, Stewart GC, OGara PT. A 52-Year-Old Man With Unheralded Syncope. JAMA Cardiol. 2017;2(12):1394–1395. doi:10.1001/jamacardio.2017.2425
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