Association Between Time to Thrombolysis and Severity of Left Ventricular Systolic Dysfunction in Patients with ST-Segment Elevation Myocardial Infarction: A Cross-Sectional Study

Abstract

Objective: Timely reperfusion is the cornerstone of treatment for ST-segment elevation myocardial infarction (STEMI), particularly in settings where primary percutaneous coronary intervention is not readily available. Delayed thrombolytic therapy may increase infarct size, impair myocardial recovery, and worsen left ventricular systolic function. This study aimed to determine the association between time to thrombolysis (TTT) and the severity of left ventricular systolic dysfunction (LVSD) among patients presenting with STEMI. Methodology: This analytical cross-sectional study was conducted at the Cardiology Unit of Khyber Teaching Hospital, Peshawar, Pakistan, between 15 May 2025 and 20 January 2026. A total of 160 consecutive adult patients presenting with STEMI within 12 hours of symptom onset and treated with thrombolytic therapy were enrolled. Time to thrombolysis was categorized into <1 hour, 1–3 hours, 3–6 hours, and 6–12 hours. Left ventricular systolic function was assessed within 24 hours using transthoracic echocardiography and categorized according to left ventricular ejection fraction (LVEF) as normal, mild, moderate, or severe dysfunction following established echocardiographic recommendations . Results: Among the 160 participants, the mean age was 59.7 ± 12.0 years, and 66.3% were male. Thrombolytic therapy was administered within <1 hour in 11.3%, 1–3 hours in 33.8%, 3–6 hours in 40.5%, and 6–12 hours in 14.4% of patients. A significant association was observed between increasing time to thrombolysis and worsening LV systolic dysfunction (p=0.001). Patients receiving thrombolysis within the first hour were more likely to have preserved ventricular function, whereas delayed reperfusion was associated with progressively greater impairment of left ventricular systolic function. Anterior myocardial infarction demonstrated a significant association with more severe LVSD (p=0.015), while gender was not significantly associated with ventricular dysfunction (p=0.149). Conclusion: Longer symptom-to-thrombolysis intervals were significantly associated with greater severity of left ventricular systolic dysfunction among patients with STEMI. These findings emphasize the importance of minimizing delays to reperfusion therapy, particularly in resource-limited healthcare settings where thrombolysis remains the principal reperfusion strategy. Owing to the cross-sectional design, the findings demonstrate association rather than causation.