INCREASED PROPENSITY OF WOMEN TO DEVELOP TORSADES-DE-POINTES DURING COMPLETE HEART-BLOCK

introduction: To determine whether an increased female gender suscepti bility to torsades de pointes (TdP) may exist in a clinical model of b radycardia-induced long QT syndrome, we investigated reported cases of TdP associated with acquired complete heart block. Methods and Result s: Seventy-two cases reported in the medical literature dating from 19 41 through 1993 were identified, all describing TdP or ''transient ven tricular tachycardia/fibrillation'' (to include those cases reported p rior to the use of TdP terminology) in the setting of acquired complet e heart block unassociated with QT prolonging drugs. Expected female p revalence in complete heart block was estimated at 52%, based on proje ctions derived from 206,016 hospital discharges in the National Inpati ent Profile (Commission on Professional and Hospital Activities, Am Ar bor, MI), over the years 1985 through 1992. During complete heart bloc k, mean heart rate was 37 beats/min in both sexes (combined n = 43), a nd absolute QT interval ranged from 0.52 to 0.88 seconds, with a mean of 0.68 seconds (n = 25). Female prevalence among patients with TdP du ring complete heart block was greater than expected: 72% for all studi ed cases (P < 0.001); 70% (P < 0.04) and 74% (P < 0.02) among those re ported prior to (n = 35) and during or after (n = 37) 1980, respective ly; 73% (P < 0.03) among those with documented normokalemia (n = 26); and 68% (P = 0.2) among those with a prolonged QT interval and known p olymorphic VT (i.e., unequivocal TdP; n = 25). Conclusion: Despite inh erent limitations of this retrospective study, the data are consistent in suggesting a greater than expected female prevalence among patient s with TdP related to complete heart block. This finding lends support to a broadening concept of increased susceptibility of women to the d evelopment of TdP in various settings of QT prolongation.