- LBBB makes most EKG's unreadable, except in those where the ST is concordant. Watch for STEMI!
- Electrical alternans can be easy to miss but may indicate an underlying effusion.
- The finding of marked axis deviation, RBBB, and prolonged PR interval is concerning for trifascicular block. In a patient with unexplained syncope this is a potentially lethal finding; admit for emergent pacemaker.