lead one ratio: a new electrocardiogram marker for cardiac resynchronization therapy response

Background: wider qrs duration and presence of left bundle branch block (lbbb) predict better cardiac resynchronization therapy (crt) response. despite strict patient selection, one-third of patients have a sub-optimal response. we aim to evaluate the impact of lead one ratio (lor) on crt response.methods: we enrolled 93 patients receiving crt from august 2016 to august 2019. pre-implant 12-lead electrocardiogram (ecg) was recorded, and lor was derived by dividing the maximum positive deflection of qrs complex in ecg lead i by the maximum negative deflection in lead i; cut-off value of 12 was used to divide the cohort into two groups. patients were followed for 6 months, and outcomes were compared for crt response, new york heart association (nyha) class improvement, all-cause mortality, and heart failure (hf) hospitalization events.results: at the end of 6-month follow-up, lor ≥ 12 was associated with significantly better crt response (75.76% vs. 51.85% in lor < 12, p = 0.02), lower mortality per 100 patient-years (9.09 vs. 14.81 in lor < 12, p = 0.012), and more improvement in hf symptoms (nyha improvement) (78.79% vs. 55.56% in lor < 12, p = 0.02). patients with lor < 12 had more hf hospitalization events (2.04 vs. 1.81 episodes in lor ≥ 12, p = 0.029) and less qrs narrowing (∆5.74 ± 2.09 vs. ∆7.10 ± 3.97 ms in lor ≥ 12, p = 0.01). qrs duration and lbbb morphology were predictors of response in both groups of patients.conclusion: lor ≥ 12 was associated with better response to crt, less hf hospitalization, and more relief in hf symptoms. this ratio helps to identify possible sub-optimal response among patients with an indication for crt.