MODE OF ONSET OF TORSADE-DE-POINTES IN CONGENITAL LONG QT SYNDROME

Objectives. We sought to describe tile mode of onset of spontaneous to rsade de pointes in the congenital long QT syndrome. Background. Conte mporary classifications of the long QT syndrome (LQTS) refer to the co ngenital LQTS as ''adrenergic dependent'' and to the acquired LQT as'( pause dependent. Overlap between these two categories has been recogni zed, and a subgroup of patients with ''idiopathic pause-dependent tors ade'' has been described. However, it is not known how commonly torsad e is preceded by pauses in the congenital LOTS. Methods, We reviewed t he electrocardiograms (ECGs) of all our patients with congenital]LOTS evaluated for syncope or sudden death (30 patients). Documentation of the onset of torsade de pointes was available for 15 patients. All the se patients had ''definitive LOTS'' by accepted clinical and ECG crite ria. Results. Pause-dependent torsade de pointes was clearly documente d in 14 of (he 15 patients (95% confidence interval 68% to 100%). The cycle length of the pause leading to torsade was 1.3 +/- 0.2 times lon ger than the basic cycle length, and most pauses leading to torsade me re unequivocally longer than the preceding basic cycle length (80% of pauses were >80 ms longer than the preceding cycle length). Conclusion s. The ''long-short'' sequence, which has been recognized as a hallmar k of torsade de pointes ill the acquired LOTS, plays a major role in t he genesis of torsade in the congenital LOTS as well. Our findings hav e important therapeutic implications regarding the use of pacemakers f or prevention of torsade in the congenital LOTS.