Cardiac Rhythm Disturbances in Patients with Left Atrial Isomerism

WU, M.‐H., et al.: Cardiac Rhythm Disturbances in Patients with Left Atrial Isomerism. This long‐term study sought to determine the clinical implication of defective sinus node and AV conduction tissue in patients with left atrial isomerism (LAI). From 1984 to 1998, a total of 22 patients were identified as LAI. Patient age at the last follow‐up ranged from 2 to 276 months (90 ± 70 months). Associated cardiac anomalies were interruption of the inferior vena cava (n = 18, 82%), common atrium (n = 9, 41%), AV canal (n = 14, 64%), double‐outlet right ventricle (n = 8, 36%), and pulmonary stenosis (n = 15, 68%). Palliative interventions were performed in 16 patients (Fontan‐type operation in 4 patients, shunt followed by Fontan‐type operation in 2, repair of septal defect in 4, and extracardiac intervention in 6). During the follow‐up, over half of the patients (n = 14, 64%) developed bradyarrhythmia (onset age: from 1 to 264 months; median 78 months): junctional rhythm (n = 11), sinus bradycardia (n= 8) (5 patients also had junctional rhythm), and AV block (n = 2, both also had junctional rhythm). The probability free from bradyarrhythmia was 80% and 46% at the age of 2 and 6 years, respectively. None of the bradyarrhythmias were directly related to open‐heart surgery. Besides, junctional ectopic tachycardia occurred after Fontan‐type operation in three of six patients. In two patients, a Mahaim‐like pathway was identified during the electrophysiological study. The patients with LAI had a high probability of developing bradyarrhythmias due to abnormal sinus node function. Varied AV conduction abnormalities may include compromised AV conduction, junctional ectopic tachycardia after Fontan‐type operation, and an association of Mahaim‐like pathway.