Distribution of Conduction Disorders in Patients With Congenital Heart Disease and Right Atrial Volume Overload

Abstract

Objectives: This study sought to quantify characteristics of atrial conduction disorders in patients with right atrial (RA) volume overload.

Background: Patients with an interatrial shunt are prone to developing atrial fibrillation (AF), which may be related to conduction disorders occurring due to atrial stretch.

Methods: Thirty-one patients undergoing surgery for an interatrial shunt (49 ± 14 years of age) underwent epicardial sinus rhythm mapping of the RA, Bachmann's bundle (BB), and left atrium (LA). Conduction delay (CD) was defined as interelectrode conduction time (CT) of 7 to 11 ms and conduction block (CB) as CT ≥12 ms. Prevalence of CD or CB (percentage of mapped region), length of lines, and severity of CB (75th percentile of CTs ≥12 ms) were analyzed.

Results: All patients had some degree of CD and CB. Prevalence of CD and CB was higher in the RA and BB than in the LA (p < 0.0083 after Bonferroni correction). The longest CB line within each patient was found in the RA in most patients (52%). Interindividual variation in prevalence and lengths of lines was considerable. CB was more severe in the RA than in the LA (p < 0.0083). Within the RA, conduction disorders were more prevalent and more severe in the intercaval region than in the RA free wall (p < 0.05).

Conclusions: In patients with an interatrial shunt, conduction disorders during sinus rhythm are most pronounced in the RA-particularly the intercaval region-and BB. Knowledge of the conduction during sinus rhythm is essential to determine the relevance of conduction disorders for initiation and perpetuation of AF.

Keywords: adult congenital heart disease; atrial septal defect; conduction disorders; epicardial mapping; sinus rhythm.