Case history
Case history #1
An 85-year-old man presents with fatigue and episodes during which he feels he is going to pass out. He has no known heart disease. His ECG shows sinus bradycardia with a rate of 30 bpm and on a rhythm strip he has up to 5-second pauses.
Case history #2
A 55-year-old man with hypertension and diabetes presents at the emergency department with complaints of dizziness and lightheadedness on exertion that has occurred gradually over the past month. He takes metoprolol (a beta-blocker) for hypertension. He is hypotensive and has a heart rate of 45 bpm. The rhythm strip shows Mobitz type II atrioventricular (AV) block with Q waves in the inferior leads. There are no previous ECGs.
Other presentations
Other diagnostic features include exercise intolerance and chest pain. Atypical presentations include elite athletes who present with sinus bradycardia, Mobitz I, or even Mobitz II atrioventricular (AV) block without symptoms owing to a conditioned heart. The condition could also manifest shortly after taking a beta-blocker, a calcium-channel blocker, or digoxin in a patient with conduction system disease. Adolescents may not have any symptoms owing to preserved left-ventricular function; by contrast, older people are more likely to manifest symptoms because of structural heart disease. Additionally, sinus bradycardia or AV nodal dysfunction could be noted incidentally on inpatient telemetry or at home using smartphone or watch sleep monitoring applications, and should prompt investigation for sleep-disordered breathing.
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