Comparison of Corrected QT Interval Prolongation in Young and Middle-aged Adults after First-time ST-Elevation Myocardial Infarction at Cardiac Care Facility: A Cross-Sectional Study

Abstract

Objective: To compare corrected QT interval prolongation in young and middle-aged adults after first-time ST-elevation myocardial infarction and to determine its association with selected clinical variables.
Study Design: Analytical cross-sectional study.
Place and Duration of Study: This study was conducted at Department of Adult Cardiology, Armed Forces Institute of Cardiology/National Institute of Heart Diseases (AFIC/NIHD), Rawalpindi, Pakistan, from 16^th October 2025 to 15^th March 2026.
Methods: A total of 296 patients with first-time ST-elevation myocardial infarction were enrolled by nonprobability consecutive sampling. Patients were classified as young adults (18-45 years) and middle-aged adults (46-65 years). Patients with previous myocardial infarction, congenital long QT syndrome, bundle branch block, paced rhythm, use of QT-prolonging drugs, severe electrolyte abnormalities other than the studied potassium variation, or incomplete clinical, electrocardiographic, laboratory, or echocardiographic data were excluded. Corrected QT interval prolongation was defined as >450 ms in males and >460 ms in females.
Results: Overall, corrected QT interval prolongation was present in 75 (25.3%) patients. Mean corrected QT interval was significantly higher in middle-aged adults than young adults (448.17±14.59 ms versus 436.84±13.91 ms; P<0.001), and corrected QT interval prolongation was more frequent in middle-aged adults (33.1% versus 17.6%; P=0.002). Prolongation was significantly associated with diabetes mellitus (P=0.049) and site of infarction (P=0.014). Patients with a prolonged corrected QT interval were older, had higher heart rates, lower serum potassium levels, and lower left ventricular ejection fractions.
Conclusion: Corrected QT interval prolongation was common after first-time ST-elevation myocardial infarction and was significantly more frequent in middle-aged adults. It may serve as a simple marker of higher clinical and electrophysiological risk, especially in patients with adverse metabolic, infarct-related, and hemodynamic factors.

How to cite this: Khaliq A, Saif M, Saif S, Rehman W, Haider R, Zaman T. Comparison of Corrected QT Interval Prolongation in Young and
Middle-aged Adults after First-time ST-Elevation Myocardial Infarction at Cardiac Care Facility: A Cross-Sectional Study. Life and Science.
2026; 7(3): 339-346. doi: http://doi.org/10.37185/LnS.1.1.1174