Factors that contribute to the QTc interval prolongation in DR-TB patients on STR regimen

Introduction: QTc interval prolongation is one of the adverse drug reaction of several drugs used in DR-TB patients treated with STR regimen. Drug-induced QTc prolongation can predispose patient to develop life-threatening arrhythmia, increasing hospital length of stay and mortality. This study aims to determine factors that contribute to QTc prolongation in DR-TB patients on STR regimen. Methods. This was an observational retrospective study using medical records of DR-TB patients who received STR regimen from August 2017 to March 2019 in tertiary hospital DR Soetomo, Surabaya, Indonesia. QTc interval was calculated by Fredericia formula. The influence of risk factors (age, body weight (BW), Body Mass Index (BMI), gender, comorbid, potassium, sodium and QTc baseline) with QTc prolongation was analyzed using multiple regression. The relationship between Moxifloxacin dosage and QTc was analyzed using Chi-Square test. Results Out of the 113 DR-TB patients who received the STR therapy regimen, 98 patients were eligible for this study. They consist of 62 (%) male; 36 (%) female. Thirty-five (35,7%) of them had Diabetes Mellitus as a comorbid disease. The mean age of the patients was 44±11 years, with the mean of BMI was 20.20± 3.73. Potassium and Sodium levels at the baseline were 4.192 ± 0.58 and 138.05 ± 4.562 respectively. The QTc baseline before receiving STR regimen was 431.9±30,617ms. Patients received a dose of moxifloxacin 400 mg (5.1%), 600 mg (59,2%), and 800 mg (35,7%) according to body weight. There were no correlation between age, BW, gender, comorbid, and sodium baseline with QTc. There were correlation between potassium (p=0,001), BMI (p=0,006) and QTc baseline (p <0,001) with QTc. Conclusion QTc baseline and potassium level are factors that contribute to the prolongation of the QTc interval.