Right bundle branch block-type wide QRS complex tachycardia with a reversed R/S complex in lead V-6: Development and validation of electrocardiographic differentiation criteria

Abstract

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 V-6 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 V-6 (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 V-6. 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 V-6 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 V-6 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 V-6. This criterion was particularly useful for the differential diagnosis of fascicular VT from RBBB pattern SVT.