Prognostic implications of intraventricular conduction disorders for sudden cardiac death in coronary artery disease

Backround and aims Prolonged QRS duration (≥ 110 ms) and coronary artery disease are risk factors for sudden cardiac death (SCD). We explored the SCD risk associated with intraventricular conduction disorders – a prolonged QRS duration of 110–119 ms, right bundle branch block (RBBB), left bundle branch block (LBBB), and a nonspecific intraventricular conduction delay (NIVCD) – in patients with acute coronary syndrome (ACS). Methods This is a retrospective study of 9,700 consecutive, invasively treated ACS patients with ECGs available for analysis (2007–2018). SCD definition was based on an in-depth review of written medical records and death certificates describing the circumstances leading to the events. Endpoint data were available until December 31, 2021 (no losses to follow-up). The risk associated with conduction disorders was analyzed by calculating subdistribution hazard estimates (deaths due to other causes being considered competing events). Results The median follow-up time was 6.8 years (IQR 4.0–10.2), during which 3,420 (35.3%) patients died. SCDs were overrepresented as a cause of death among patients with NIVCD (16.4%) or with a prolonged QRS duration (15.3%) when compared to patients with LBBB (5.3%), RBBB (7.1%), or with a normal QRS duration (10.5%). In an analysis adjusted for age, sex, and cardiac comorbities, NIVCD and a prolonged QRS were significant predictors of SCD (HR 3.00, 2.06– 4.35, P < 0.001; and HR 1.80, 1.37–2.35, P < 0.001, respectively). After adjusting the analysis with left ventricular ejection fraction, NIVCD and a prolonged QRS duration remained as significant risk factors for SCD. LBBB and RBBB did not predict SCD. Conclusion The incidence of SCD is significantly higher in patients with NIVCD and a prolonged QRS duration. Approximately 23% of all SCDs occur among these patients.