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

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.

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