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.

Abstract Background Differentiation of supraventricular tachycardia (SVT) with 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 (ECG) criteria for distinguishing between these arrhythmias. Methods We investigated ECG parameters from 111 consecutive patients who had RBBB-pattern wide QRS complex tachycardia (WCT) 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 to the nadir of 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, Vereckei, 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 0.41 differentiated VT from SVT with a high diagnostic accuracy (sensitivity:97.2%, specificity:89.7%). When tested in a prospective population of fascicular VT, 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 an RBBB-pattern WCT with a reversed R/S complex in lead V6. This criterion was particularly useful for differential diagnosis of fascicular VT from RBBB-pattern SVT.