Ventricular tachycardia (VT) can be difficult to differentiate from supraventricular tachycardia with aberrancy. When in doubt, it is safest to treat most wide complex tachycardia as VT. Up to 80% of cases of all WCT are ventricular tachycardia, and none of the available algorithms perform well in the acute setting. One should be cautious of treating potential VT with atrioventricular nodal blockers (as one would for SVT).
VT vs SVT with Aberrancy – the CRAM Mnemonic. This mnemonic is adapted from the Brugada algorithm, which is one of several algorithms to help differentiate between supraventricular tachycardia with aberrancy and ventricular tachycardia. Concordance describes the situation where QRS complexes are in the same direction (up or down) across the entire precordium (V1 – V6); if this condition is met, ventricular tachycardia is diagnosed. If the beginning of the R wave to the nadir of the S is greater than 100 ms, ventricular tachycardia is diagnosed. If there are signs of AV dissociation (i.e., capture beats, fusion beats, or occasionally P waves can be visualized), ventricular tachycardia is diagnosed. Finally, if the previous three criteria are not met and the morphology suggests aberrancy then ventricular tachycardia is unlikely. Rsr’ appearance (as opposed to rsR’) in V1 strongly favors ventricular tachycardia. AV, atrioventricular.