Torsade de Pointes: A Nested Case Control Study in an Integrated Health Care Delivery System

Background: TdP is a form of polymorphic ventricular tachycardia which develops in the setting of a prolonged QT interval. There is limited data describing risk factors, treatment and outcomes of this potentially fatal arrhythmia. Objective: Our goals were: 1) to validate cases presenting with Torsade de Pointes (TdP); 2) to identify modifiable risk factors; and 3) to describe the management strategies used for TdP and its prognosis in a real-world health care setting. Methods. Case-control study (with 2:1 matching on age, sex and race/ethnicity) nested within the Genetic Epidemiology Research on Aging (GERA) cohort. Follow-up of the cohort for case ascertainment was between 01/01/2005 and 12/31/2018. Results. A total of 56 cases of TdP were confirmed (incidence rate= 3.6 per 100,000 persons/years). The average (SD) age of the TdP cases was 74 (13) years, 55 percent were female and 16 percent non-white. The independent predictors of TdP were potassium concentration 480 ms (OR=4.4) and prior history of coronary artery disease (OR=2.6). Exposure to furosemide and amiodarone were significantly greater in cases than in controls. The most common treatment for TdP was IV magnesium (78.6%) and IV potassium repletion (73.2%). The in-hospital and 1-year mortality rates for TdP cases were 10.7% and 25.0% percent, respectively. Conclusions. These findings may inform quantitative multivariate risk indices for the prediction of TdP and could guide practitioners on which patients may qualify for continuous ECG monitoring and/or electrolyte replacement therapy.