QRS morphology in lead V1 for the rapid localization of idiopathic ventricular arrhythmias originating from the left ventricular papillary muscles: A novel electrocardiographic criterion

BACKGROUND Twelve-lead electrocardiogram (ECG) criteria have been developed to identify idiopathic ventricular arrhythmias (VAs) from the left ventricular (LV) papillary muscles (PAPs), but accurate localization remains a challenge. OBJECTIVE The purpose of this study was to develop ECG criteria for accurate localization of LV PAP VAs using lead V-1 exclusively. METHODS Consecutive patients undergoing mapping and ablation of VAs from the LV PAPs guided by intracardiac echocardiography from 2007 to 2018 were reviewed (study group). The QRS morphology in lead V-1 was compared to patients with VAs with a "right bundle branch block" morphology from other LV locations (reference group). Patients with structural heart disease were excluded. RESULTS One hundred eleven patients with LV PAP VAs (mean age 54 +/- 16 years; 65% men) were identified, including 64 (55%) from the posteromedial PAP and 47 (42%) from the anterolateral PAP. The reference group included patients with VAs from the following LV locations: fascicles (n = 21), outflow tract (n = 36), ostium (n = 37), inferobasal segment (n = 12), and apex (5). PAP VAs showed 3 distinct QRS morphologies in lead V-1 93% of the time: Rr (53%), R with a slurred downslope (29%), and RR (11%). Sensitivity, specificity, positive predictive value, and negative predictive value for the 3 morphologies combined are 93%, 98%, 98%, and 93%, respectively. The intrinsicoid deflection of PAP VAs in lead V-1 was shorter than that of the reference group (63 +/- 13 ms vs 79 +/- 24 ms; P < .001). An intrinsicoid deflection time of <74 ms best differentiated the 2 groups (sensitivity 79%; specificity 87%). CONCLUSION VAs originating from the LV PAPs manifest unique QRS morphologies in lead V-1, which can aid in rapid and accurate localization.