The differential for wide complex tachycardia includes ventricular tachycardia (VT), supraventricular tachycardia (SVT, e.g., atrial flutter, atrial tachycardia, or atrioventricular nodal reentrant tachycardia) with aberrancy (i.e., bundle branch block), antidromic atrioventricular reentrant tachycardia, and toxicologic/metabolic disturbances (e.g., sodium-channel blockade, hyperkalemia). There are obvious perils of missing VT, and the test characteristics of the various criteria for differentiating VT vs SVT with aberrancy may be insufficient given the serious implications of falsely diagnosing SVT. Therefore, unless there is a compelling alternative, VT should be assumed.
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.