QRS duration, left bundle branch block morphology, and outcomes among patients who undergo septal myectomy.

BACKGROUND

The clinical impact of new-onset left bundle branch block (LBBB) and QRS duration after septal myectomy remains unclear.

OBJECTIVE

This study investigated effects of LBBB morphology and QRS duration on long-term outcomes after septal myectomy.

METHODS

This study analyzed 1655 patients with hypertrophic cardiomyopathy (HCM) without preoperative conduction disorders who underwent septal myectomy. Patients were stratified into 3 groups according to the postoperative QRS features: no LBBB, LBBB with QRS <150 milliseconds, and LBBB with QRS ≥150 milliseconds. Outcomes included mortality, permanent pacemaker implantation, and left ventricular systolic dysfunction (LVSD, left ventricular ejection fraction <50%). Cox models adjusted for clinical and echocardiographic variables assessed risk.

RESULTS

LBBB occurred in 50% of patients. During 55-month follow-up, LBBB and QRS ≥150 milliseconds was associated with highest risks of all-cause mortality (adjusted HR = 2.17, 95% CI 1.12-4.20; P = .022) and pacemaker implantation (adjusted HR = 4.36, 95% CI 1.69-11.29; P = .002), compared with those without LBBB. Five-year survival free from mortality was lowest in the LBBB and QRS ≥150 milliseconds group (97.2% vs 98.0% and 98.9% in no LBBB and LBBB and QRS <150 milliseconds groups; P < .001). LVSD risk was higher in patients with LBBB and QRS ≥150 milliseconds (adjusted HR 7.04, 95% CI 3.00-16.50; P < .001) than in those without LBBB.

CONCLUSION

In conclusion, although overall survival remains excellent, new-onset LBBB with QRS ≥150 milliseconds after septal myectomy identifies an HCM subgroup at higher risk for LVSD, warranting closer monitoring and timely intervention.