Heart Blocks ECG Quiz 18 Answer

1. Atrial fibrillation with an uncontrolled ventricular response
2. Left bundle branch block
3. Premature ventricular contractions

At times it can be difficult to distinguish "SVT with aberrancy" from ventricular tachycardia. This QRS morphology has a typical left bundle branch block pattern, is irregular and does not meet the Brugada criteria for ventricular tachycardia (see the ventricular tachycardia review below).

One of the Brugada morphology criteria to diagnose ventricular tachycardia when the QRS pattern is similar to a left bundle branch block is a wide R wave in lead V1 or V2 measuring > 40 ms (one little box). This is not the case in the QRS complex on this ECG, except for the one beat in lead V1 towards the end of the ECG strip. This beat is one of the premature ventricular contractions and does have a wide R wave measuring about 80 ms and is in a left bundle pattern, thus this beat alone is ventricular in origin (not the rest of the QRS complexes which are simply a left bundle branch block of supraventricular origin).

LBBB-VT-Morphology

Related Topic Reviews: Left Bundle Branch Block, Premature Ventricular Contraction, Ventricular Tachycardia