Interatrial block is an independent risk factor for new-onset atrial fibrillation after cardiac surgery.

Objectives: This study aims to investigate the association between interatrial conduction block and postoperative atrial fibrillation, which can precipitate acute cardiopulmonary instability and is associated with subsequent heart failure, stroke, and mortality following cardiac surgery.

Methods: Perioperative 12-channel electrocardiograms from 3405 patients undergoing myocardial revascularization, valve surgery, aortic surgery, or combinations thereof, were considered. Clinical and electrographic parameters were compared between patients with and without atrial fibrillation, and significant variables were analyzed using univariate and multivariate logistic regression.

Results: Among 2108 analyzed patients, 764 (36.2%) developed atrial fibrillation. Preoperative interatrial block was a strong independent risk factor (3.18; 95% CI, 2.55, 3.96; P < .001), significantly improving area under the receiver operator characteristics curve from 71.8% to 75.6% (Delong's test: P = .013). Other risk factors included advanced age (1.05; 95% CI, 1.03, 1.07; P < .001), female gender (1.86; 95% CI, 1.45, 2.38; P < .001), history of cardiogenic shock (1.44; 95% CI, 0.99, 2.09; P = .057), reduced left ventricular ejection fraction <40% (1.57; 95% CI, 1.06, 2.33; P = .024), cessation of preoperative β-blockers (1.17; 95% CI, 0.95, 1.46; P = .145), score for clinical prediction rules for estimating the risk of stroke in people with non-rheumatic atrial fibrillation (CHAS₂DS₂-VASc) and European System for Cardiac Operative Risk Evaluation II score (0.87; 95% CI, 0.79, 0.97; P = .01) and (1.04; 95% CI, 0.99, 1.11; P = .138), preexisting left bundle branch block (1.59; 95% CI, 0.92, 2.74; P = .097), cardiopulmonary bypass time (1.00; 95% CI, 1.00, 1.00; P = .049), bicaval cannulation (1.45; 95% CI, 0.88, 2.41; P = .035), cardiac surgery-associated acute kidney injury (3.19; 95% CI, 2.45, 4.15; P < .001), and postoperative atrioventricular block (1.20; 95% CI, 0.96, 1.51; P = .105), particularly Mobitz I (6.73; 95% CI, 1.98, 31.51; P = .005).

Conclusions: Perioperative electrocardiogram-derived parameters, especially interatrial block, are associated with postoperative atrial fibrillation. Further research is needed to clarify the link between conduction abnormalities and postoperative atrial fibrillation, enabling targeted prophylactic therapies for high-risk patients.