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

Abstract

Objectives: 1) To validate cases presenting with Torsade de Pointes (TdP) and compare these cases to age-, sex-, and race/ethnicity (2 to 1) matched-controls in order to identify modifiable risk factors; and 2) Describe the management strategies used for TdP and its prognosis in a real-world health care setting. Background: TdP is a form of polymorphic ventricular tachycardia which develops in the setting of a prolonged QTc interval. There is limited data describing risk factors, treatment and outcomes of this potentially fatal arrhythmia. Results: Using the Genetic Epidemiology Research on Aging (GERA) cohort (n=110,266) and follow-up between 01/01/2005 and 12/31/2018, a total of 56 cases of TdP were confirmed (incidence rate= 3.6 per 100,000 persons/year. 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 prior history of heart failure (OR=5.7), supraventricular arrhythmias (OR=3.6) and potassium concentration < 3.6 mEq/L (OR=10). On average, TdP cases were preceded by 48 ms prolongation of the QTc. 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.