SUPRAVENTRICULAR TACHYCARDIA IN PATIENTS WITH RIGHT ATRIAL ISOMERISM

Objectives. To clarify the prevalence and mechanism of supraventricula r tachycardia in patients with right atrial isomerism. Background. Pai red SA and dual atrioventricular (AV) nodes have been described in pat ients with right atrial isomerism. However, the clinical significance remains unclear. Methods. From 1987 to 1996, a total of 101 patients ( 61 male, 40 female) and four fetuses were identified with right atrial isomerism. The diagnosis of supraventricular tachycardia exclude the tachycardia with prolonged QRS duration or AV dissociation, and primar y atrial tachycardia. Results. The median follow-up duration,vas 38 mo nths (range 0.2-270 months). Supraventricular tachycardia was document ed in 25 patients (24.8%) and one fetus (25%) (onset age ranged from p renatal to 14 years old; median 4 years old). Actuarial Kaplan-Meier a nalysis revealed that the probability of being free from tachycardia w as 67% and 50% at 6 and 10 years of age, respectively. These tachycard ias could be converted by vagal maneuvers in one, verapamil in seven, propranolol in four, digoxin in two, procainamide in one, and rapid pa cing in five. Spontaneous conversion was noted in six (including the f etus). Seven cases had received electrophysiological studies. Reciproc ating AV tachycardia could be induced in five and echo beats in one. T he tachycardia in three patients was documented as incorporating a pos terior AV node (antegrade) and an anterior or a lateral AV node (retro grade). Two of them received radiofrequency ablation. Successful ablat ion in both was obtained by delivering energy during tachycardia, aime d at the earliest retrograde atrial activity and accompanied by juncti onal ectopic rhythm. The patient with echo beats developed tachycardia soon after operation. Conclusions. Supraventricular tachycardia is co mmon in patients with right atrial isomerism and can occur during the prenatal stage. Drugs to slow conduction through the AV node may help to terminate the tachycardia, Radiofrequency ablation is a safe and ef fective treatment alternative to eliminate tachycardia. (J Am Coll Car diol 1998;32:773-9) (C)1998 by the American College of Cardiology.