SPONTANEOUS SEQUENCES OF ONSET OF TORSADE-DE-POINTES IN PATIENTS WITHACQUIRED PROLONGED REPOLARIZATION - QUANTITATIVE-ANALYSIS OF HOLTER RECORDINGS

Objectives. This study investigated the cycle length changes preceding the spontaneous onset of torsade de pointes in patients with acquired prolonged ventricular repolarization. Background. Torsade de pointes is a polymorphic ventricular tachycardia generally associated with pro longed ventricular repolarization. Because torsade de pointes is not i nducible by programmed electrical stimulation, quantitative analysis o f Holter recordings of spontaneous episodes may clarify the mechanisms favoring the onset of torsade de pointes in actual clinical condition s. Methods. The digitized Holter recordings of 12 patients were analyz ed by a computerized Holter system (ATREC). All arrhythmias were group ed according to three classes: 1) isolated premature ventricular beats (n = 47,147, mean/patient [+/-SD] 3,929 +/- 11,571); 2) salves of 2 t o 4 consecutive beats (n = 2,003, mean/patient 167 +/- 359); 3) torsad e de pointes greater than or equal to 5 beats (n = 105, mean/patient 9 +/- 11). For each patient and class of arrhythmias, six variables wer e computed from the 10 min and the 10 cycles preceding the event onset . Results. A significant heart rate increase in the last minute (p < 0 .01) and typical oscillatory short-long-short cycle length sequences p receded the onset of arrhythmias, with greater oscillation preceding t orsade de pointes than salves and premature ventricular beats. The cyc le lengths preceding the onset were highly correlated with the class o f arrhythmias (r = 0.65, p < 0.005) and allowed the correct classifica tion of 69% of events by discriminant analysis (p < 0.0001). A signifi cant negative correlation,vas observed between the duration of torsade de pointes and the mean length of the initial cycles (r -0.62, p < 0. 001), indicating that longer torsade de pointes had a faster rate than that at onset. Conclusions. In patients with acquired prolonged repol arization, the spontaneous onset of ventricular arrhythmias was preced ed by an increasing heart rate in the last minute and escalating oscil latory ''short-long-short'' cycle length patterns, with greater oscill ations preceding torsade de pointes than salvos and isolated ventricul ar beats. These findings suggest that adrenergic- and pause-dependent mechanisms (possibly inducing afterdepolarizations and triggered activ ity) may have a synergetic role in the genesis of complex ventricular arrhythmias associated with delayed ventricular repolarization.