複雜性先天心臟病術前術後心律不整之電生理學機轉：以同步電位及之體結構定位法研究(1/3)

Objectives. To determine the prevalence and the electrophysiological mechanisms of rhythm disturbances in patients with left atrial isomerism (LAI). Background. Defective sinus node and atrioventricular conduction tissue have been described in the hearts associated with LAI. Methods. From 1984 to 1998, a total of 22 patients, and from 1995 to 1998, 3 fetuses, were identified as LAI and constituted the study population. Pathological confirmation was obtained in 14 patients and 1 fetus. Results. The age at the last follow-up ranged from 2 to 276 months (90± 70 months). Three fetuses (100%) developed sinus bradycardia and intermittent AV block, and were ended with heart failure and termination. Associated cardiovascular anomalies of the 22 pediatric patients were interruption of inferior vena cava (18, 82%), common atrium (9, 41%), AV canal (14, 64%), double-outlet right ventricle (8, 36%) and pulmonary stenosis (15, 68%). Over half of the patients (14, 64%) developed bradyarrhythmia (onset age, 1 to 264 months, median 78 months): junctional escape rhythm as dominant rhythm, 10 (45%), sinus bradycardia or sinoatrial block, 8 (35%, 5 of the 7 also had dominant junctional rhythm) and AV block, 2 (9%, both had dominant junctional rhythm). By actuarial analysis, the probability free from bradyarrhythmia decreased with age and was 80% and 46% at the age of 2 and 6 years, respectively. Two patients experienced fainting attacks. However, junctional ectopic tachycardia after the cardiac operation occurred in 3 out of 10 patients. Electrophysiological studies (3 cases) revealed sinus node dysfunction in 2/2 and impaired AV conduction in 1/2. Besides, a Mahaim-like pathway (progressive shortening of HV interval during decremental atrial pacing) was identified in both of the patients with His potential recorded during the study.Conclusions. Over half of the LAI patients may develop bradyarrhythmia at the age of 6 years mainly due to the subnormal sinus node function. Bradyarrhythmia appeared during the fetal stage may cause preferential loss of the fetuses. Patients with LAI also have a higher chance to have junctional tachycardia which may be related to the abnormal AV conduction properties. The high prevalence of Mahaim-like pathway warrants further investigation