Incremental Value of JTc Interval in Improving Risk Stratification for Life-Threatening Ventricular Arrhythmias in Patients Considered Low Risk by LVEF

Introduction: ICD implantation is recommended in patients with LVEF<35%, while those with LVEF between 35 to 40% are not considered at high risk for primary prevention ICD implantation. A subset of these patients develops life threatening ventricular arrhythmias (VA) and improvement in risk stratification may help identify and implement life-saving intervention. Hypothesis: Prolonged repolarization is a marker of electrical instability and JTc interval on ECG could provide prognostic information in patients with LVEF 35-40% incremental to that from LVEF. Methods: Patients ≥18 yr with no history of VA and an ECG and echocardiogram obtained at initial encounter between 11/2011 to 12/2016 with long-term follow-up were identified. The incremental predictive ability of JTc interval on improvement in risk stratification for VA was determined by receiver operating characteristics (ROC) curve, integrated discrimination improvement (IDA) and net reclassification improvement (NRI) analysis. All tests were performed at a 5% level of significance. Results: Out of 29,700 pts that met inclusion criteria, 1,102 (3.7%) had LVEF 35-40% (mean age 70.5±14.6 yrs, 49% males, CAD 67%) and 24,894 (84%) LVEF >40% (65.9±16.3 yrs , 61.8% M). Over the mean follow-up of 4.6±4.2 years, the incidence of VT/VF/cardiac arrest was 16.1% in patients with LVEF 35-40% compared to 4.1% with LVEF >40%. For every 50 ms increase in JTc interval above 300 ms, the risk for arrhythmic event in LVEF 35-40% increased two-fold (Odds Ratio=1.83 (95 % CI 1.72-1.94, P=0.013). Incorporation of JTc to LVEF improved the C statistics (95% Confidence Limit) in the model with only LVEF from 0.56 (0.54-0.57) to 0.72 (0.70-0.73) for the model combining LVEF and JTc. In addition, NRI was estimated at 0.57, which was statistically significant with p values <0.001 while IDI was estimated as 0.015 with p values <0.001 for the model incorporating JTc to LVEF. Conclusions: In patients with LVEF 35-40% considered low risk for life threatening VA by EF, incorporating JTc interval information improved risk stratification and identified those who subsequently developed VT/VF or cardiac arrest and thus identifies a subgroup that can benefit from prophylactic ICD implantation.