Cardiac rhythm disturbances in patients with left atrial isomerism

This long-term study sought to determine the clinical implication of defect ive sinus node and AV conduction tissue in patients with left atrial isomer ism (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 ven a cava (n = 18, 82%), common atrium (n = 9, 41%), AV canal (n = 14, 64%), d ouble-outlet right ventricle (n = 8, 36%), and pulmonary stenosis (n = 15, 68%). Palliative interventions were performed in 16 patients (Fontan-type o peration in 4 patients, shunt followed by Fontan-type operation in 2, repai r of septal defect in 4, and extracardiac intervention in 6). During the fo llow-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 fr om bradyarrhythmia was 80% and 46% at the age of 2 and 6 years, respectivel y. None of the bradyarrhythmias were directly related to open-heart surgery . Besides, junctional ectopic tachycardia occurred after Fontan-type operat ion in three of six patients. In two patients, a Mahaim-like pathway was id entified 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 co nduction, junctional ectopic tachycardia after Fontan-type operation, and a n association of Mahaim-like pathway.