RBBB Type Wide QRS Complex Tachycardia with a Reversed R/S complex in Lead V6: Electrocardiographic Differentiation of Supraventricular Tachycardia from Ventricular Tachycardia

Abstract

Objective Supraventricular tachycardia (SVT) may manifest as a wide QRS complex tachycardia (WCT). Differentiation of SVT with a right bundle branch block (RBBB) pattern from ventricular tachycardia (VT) is difficult particularly when R/S ratio in lead V6 is below 1.0. We sought to investigate the ECG criteria for distinguishing these two arrhythmias. Methods We investigated ECG parameters from a total of 111 consecutive patients with RBBB pattern WCT with a reversed R/S ratio in lead V6 (72 VTs and 39 SVTs). Arial flutter was diagnosed by visible flutter waves with variable atrioventricular conduction during treadmill test/adenosine infusion or reproduction of WCT by atrial overdrive pacing at the cycle length of clinical tachycardia. Diagnostic criteria from the previous algorithms were compared with our new criteria, RS/QRS ratio, which was defined as the ratio of QRS waveform durations, measured by the interval from the onset of the QRS to the nadir of S wave divided by the total QRS width in the precordial lead V6. Results The diagnostic accuracy of previous criteria (Brugada criteria, Vereckei criteria, R-wave peak time at lead II) was only modest (sensitivity; 80.6%, 90.3%, 48.6%, specificity; 30.8%, 61.5%, 92.3%, respectively). However, RS/QRS ratio in lead V6 was significantly lower in SVT than in VT (0.36±0.04 vs 0.50±0.08, P <0.001). On receiver operating characteristic curve analysis, cutoff value of the RS/QRS ratio >0.41 differentiated WCT with a high diagnostic accuracy (sensitivity; 97.2%, specificity; 89.7%). Conclusions RS/QRS ratio >0.41 in lead V6 is a simple and reliable index distinguishing VT from SVT in patients with a RBBB pattern WCT and a reversed R/S complex in lead V6.