Right bundle branch block-type wide QRS complex tachycardia with a reversed R/S complex in lead V₆: Development and validation of electrocardiographic differentiation criteria

Background: Differentiation of supraventricular tachycardia (SVT) with a right bundle branch block (RBBB) pattern from ventricular tachycardia (VT) is difficult, particularly when the R/S ratio in lead V₆ is below 1.0.

Objective: We sought to investigate the electrocardiographic criteria for distinguishing between these arrhythmias.

Methods: We investigated electrocardiographic parameters from 111 consecutive patients who had RBBB pattern wide QRS complex tachycardia with a reversed R/S ratio in lead V₆ (72 VTs, 39 SVTs). Diagnostic criteria from the previous algorithms were compared with our new criterion, the RS/QRS ratio, which was defined as the ratio of the interval from the onset of the QRS complex to the nadir of the S wave, divided by the QRS width in lead V₆. The RS/QRS ratio was further tested in a prospective population (31 fascicular VTs, 29 SVTs).

Results: The diagnostic accuracy of previous criteria (Brugada algorithm, Vereckei algorithm, and R-wave peak time criterion) was only modest. However, the RS/QRS ratio in lead V₆ was significantly lower in SVT than in VT (0.36 ± 0.04 vs 0.50 ± 0.08; P < .001). A cutoff value of the RS/QRS ratio >0.41 differentiated VT from SVT with a high diagnostic accuracy (sensitivity 97.2%; specificity 89.7%). When tested in a prospective population with fascicular VT, the diagnostic accuracy of the criteria was maintained (sensitivity 90.3%; specificity 86.2%).

Conclusion: The RS/QRS ratio >0.41 in lead V₆ is a simple and reliable index for distinguishing VT from SVT in RBBB pattern wide QRS complex tachycardia with a reversed R/S complex in lead V₆. This criterion was particularly useful for the differential diagnosis of fascicular VT from RBBB pattern SVT.