Postoperative changes in QRS duration and long-term mortality after septal myectomy

To evaluate whether change in QRS duration (ΔQRS), defined as postoperative QRS duration minus preoperative QRS duration, after septal myectomy for obstructive hypertrophic cardiomyopathy (oHCM) has prognostic significance for all-cause mortality.

We performed a retrospective, single-center cohort study of patients with oHCM who underwent transaortic septal myectomy between July 23, 2009, and July 30, 2020, with available preoperative and early postoperative (days 4-7) electrocardiography (ECG) data. Patients with a preoperative or postoperative permanent pacemaker were excluded. The primary outcome was all-cause mortality. Multivariable Cox models were adjusted for age, sex, operative time, major concomitant surgery, and preoperative right bundle branch block. ECG analyses examined preoperative QRS duration, ΔQRS (postoperative minus preoperative QRS), and, in exploratory models, postoperative left bundle branch block (LBBB) and absolute postoperative QRS duration.

Among 1143 patients (1141 in complete-case multivariable analyses), the mean preoperative QRS duration was 129.5 ± 25.4 ms and increased modestly postoperatively (133.5 ± 26.0 ms); the mean ΔQRS was 4.0 ± 12.8 ms. A total of 122 deaths occurred during follow-up. Preoperative QRS duration was not associated with mortality (hazard ration [HR] per 10 ms, 1.01; 95% confidence interval [CI], 0.94-1.09; P = .78). In contrast, greater ΔQRS was independently associated with higher mortality (HR per 10 ms, 1.16; 95% CI, 1.01-1.34; P = .037), including after adjustment for preoperative QRS duration. Threshold analyses demonstrated increased risk with ΔQRS ≥0 ms (HR, 1.88; 95% CI, 1.17-3.03; P = .009) and ΔQRS ≥10 ms (HR, 1.84; 95% CI, 1.26-2.68; P = .001). Absolute postoperative QRS duration ≥150 ms was not associated with mortality (HR, 1.14; 95% CI, 0.76-1.71; P = .52). In exploratory comparison models, ΔQRS showed a stronger and more consistent association with mortality compared to postoperative LBBB or absolute postoperative QRS duration.

ΔQRS following transaortic septal myectomy for oHCM was independently associated with all-cause mortality. In exploratory comparison models, ΔQRS showed a stronger and more consistent association with mortality compared to postoperative LBBB or absolute postoperative QRS duration. ΔQRS may represent a simple, clinically available marker to enhance postoperative risk stratification following septal myectomy for oHCM.