Syncope can be caused by a cardiac arrhythmia. The presence of certain ECG changes can help identify a patient with arrhythmic syncope.


Some patients will have a history of palpitations preceding the syncopal episode.

ECG changes


(1) presence of Q waves

acute myocardial infarction

(2) negative T waves in the right precordial leads, epsilon waves, and ventricular late potentials

arrhythmogenic right ventricular dysplasia

(3) right bundle range block with ST-elevation in V1, V2 and V3

Brugada syndrome

(4) bifascicular block


(5) pre-excited QRS complexes


(6) prolonged QT interval

may be drug-induced

(7) biventricular block


(8) QRS duration >= 0.12 seconds

other intraventricular conduction abnormalities

(9) Mobitz type I second degree atrioventricular (AV) block


(10) sinoatrial block


(11) asymptomatic sinus bradycardia with heart rate < 50 beats per minute




• Biventricular block is defined as (either left bundle branch block or right bundle branch block) AND (either left anterior OR left posterior fascicular block).


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