Mode of onset of torsade de Pointes in congenital long QT syndrome

Objectives. We sought to describe the mode of onset of spontaneous torsade de Background. Contemporary classifications of the long QT syndrome (LQTS) refer to the congenital LQTS as ''adrenergic dependent'' and to the acquired LQT as'(pause dependent. Overlap between these two categories has been recognized, and a subgroup of patients with ''idiopathic pause-dependent torsade'' has been described. However, it is not known how commonly torsade is preceded by pauses in the congenital LOTS. Methods, We reviewed the 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 these patients had ''definitive LOTS'' by accepted clinical and ECG criteria. Results. Pause-dependent torsade de pointes was clearly documented 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 longer than the basic cycle length, and most pauses leading to torsade mere unequivocally longer than the preceding basic cycle length (80% of pauses were >80 ms longer than the preceding cycle length). Conclusions. The ''long-short'' sequence, which has been recognized as a hallmark of torsade de pointes in the acquired LOTS, plays a major role in the genesis of torsade in the congenital LOTS as well. Our findings have important therapeutic implications regarding the use of pacemakers for prevention of torsade in the congenital LOTS.