Bradyarrhythmias: diagnostics

Bradyarrhythmias cause symptoms such as syncope, dizziness, or exercise intolerance and lead to the implantation of > 100 000 pacemakers in Germany annually. They are caused either by sinus node dysfunction (sinus bradycardia, sinoatrial block, sinusarrest, preautomatic pauses in paroxysmal atrial fibrillation, chronotropic incompetence) or by atrioventricular (AV) conduction abnormalities (AV block, complex bundle branch block). Optimal therapy of bradycardia crucially depends on ECG documentation which frequently requires Holter monitoring in the case of intermittent bradycardia. The differential diagnosis of the ECG can sometimes be demanding, for instance in distinguishing sinus bradycardia or AV block from blocked supraventricular premature beats, in understanding chronotropic sinus node incompetence, 2:1 AV block, complete AV block in atrial fibrillation, bifascicular and imminent trifascicular bundle branch block or vagally induced bradycardia. This review presents the ECG in bradycardia and provides tips for a confident interpretation.