Analysis of drugs effects on QTc interval prolongation in critically ill patients in intensive care units

Introduction: The QTc interval is considered extended if its duration is longer than 460 ms for men, or 470 ms for women. Its prolongation is an often-underdiagnosed condition with a higher prevalence than clinicians realize. Numerous drugs can prolong the QTc interval. Aim: The aim of this study was to analyze the impact of drug interactions on prolonging the QTc interval in critically ill patients. Material and methods: This is a cross-sectional observational study with retrospective data collection of adult patients admitted to one of the three intensive care units (ICU) of the Clinical Hospital Center "Bezanijska kosa" from April to September 2022. To identify risk factors for the development of a prolonged QTc interval, patient variables were compared between patients with prolonged and those with normal QTc intervals. Results: A number of 166 patients of average age 70.7 ± 12.2 years were included in the study of whom 45.2% were women. The overall prevalence of QTc prolongation was 42.8% (71/166; 95% CI = 35.1%-50.7%). When analyzed by gender, the prevalence was 50.5% (95% CI = 39.9%-61.2%) in men and 33.3% (95% CI = 22.9%-45.2%) in women. The difference between men and women was not statistically significant (p = 0.12). During their stay in the ICU, 32 patients (19.3%, 95% CI = 13.6%-26.1%) were prescribed two drugs known to be associated with QTc interval prolongation. Among patients with prolonged QTc intervals, 27 out of 32 (84.4%, 95% CI = 67.2%-94.7%) received these drugs, compared to 5 out of 32 patients (15.6%, 95% CI = 5.3%-32.8%) with normal QTc interval duration who received the same drugs. Conclusion: The study showed a high prevalence of prolonged QTc interval in critically ill patients and pointed to the most likely existence of a higher risk of its prolongation when drugs whose interaction can lead to its prolongation are used at the same time.