Prognostic implications of intraventricular conduction disorders for the risk of sudden cardiac death in cardiac patients

BACKGROUND: QRS duration is associated with sudden cardiac death (SCD). The prognostic implications of different intraventricular conduction disorders (IVCDs) are unclear. OBJECTIVE: We explored the risk of SCDs associated with prolonged QRS (110-119 ms), right bundle branch block, left bundle branch block (LBBB), and nonspecific IVCD (NIVCD) in cardiac patients. METHODS: We analyzed the data from 4 cohorts comprising data of 26,028 cardiac patients undergoing either coronary angiography or clinical exercise testing. The median follow-up time for SCD events was 8.4 years (5.5-11.6). SCD events were classified according to strict criteria and full access to all written medical records including results of medicolegal autopsies. IVCDs were classified by researchers blinded to outcome data. The risk associated with IVCDs compared with normal QRS (<110 ms) was calculated using subdistribution hazard (SDH) analysis. RESULTS: SCDs occurring in patients with IVCD (19.2% of all patients; n = 5007) accounted for 33% of all SCDs (30%-36%) (n = 1162 events). In age- and sex-adjusted analysis, NIVCD showed the strongest association with SCD (SDH 2.7; 95% confidence interval [CI] 2.1-3.6; P < .0001), followed by LBBB (SDH 2.0; 95% CI 1.5-2.6; P < .0001), prolonged QRS (SDH 1.9; 95% CI 1.6-2.3; P < .0001), and right bundle branch block (SDH 1.5; 95% CI 1.1-1.9; P = .003). NIVCD and prolonged QRS also associated significantly with SCD despite adjusting for baseline clinical risk factors and left ventricular ejection fraction (LVEF). LBBB associated significantly with SCD after adjusting for risk factors but not after adjusting for LVEF. CONCLUSION: NIVCD and prolonged QRS are strong predictors of SCD events despite adjusting for risk factors including LVEF.