Sinus rhythm ECG criteria associated with basal-lateral ventricular tachycardia substrate in patients with nonischemic cardiomyopathy

Introduction: Patients with nonischemic cardiomyopathy (NICM) and ventricular tachycardia (VT) usually have basal-lateral scar in the left ventricle (LV). We sought to determine electrocardiogram (ECG) characteristics that may help identify NICM patients with basal-lateral scar and VT. Methods and Results: Phase I, study patients (n = 25) had NICM, VT, and endocardial/epicardial basal-lateral LV low voltage consistent with scar on detailed mapping. ECGs were compared to controls (n = 18) with NICM, and comparable age and gender without VT/known scar. All patients had either sinus or paced atrial rhythm ECGs without bundle-branch block or ventricular pacing. In phase II, criteria were evaluated prospectively, blinded to clinical data, using ECGs from 15 NICM patients, of which 7 patients had VT and endocardial/epicardial basal-lateral LV scar on detailed mapping. Of ECG characteristics studied, V1 R and R:S ratio, and V6 S and S:R ratio were univariately associated with basal-lateral-scar associated VT. Controlling for LVEF and multicollinearity in multivariate analyses, V1 R ≥ 0.15 mV (P = 0.001) and V6 S ≥ 0.15 mV (P < 0.001), or V6 S:R ≥ 0.2 mV (P < 0.001), best predicted presence of basal-lateral scar. In Phase II, the former criteria best identified those with NICM and VT because of basal-lateral scar, with sensitivity and specificity 0.86 and 0.88, respectively. Conclusions: Among patients with NICM, VT, and normal QRS duration, V1 R ≥ 0.15 mV and V6 S ≥ 0.15 mV predicted presence of basal-lateral LV areas of bipolar low voltage. This ECG information may have important value in defining presence of LV scar and possible risk for VT in NICM patients.