An Improved Rat Model of Myocardial Infarction Without Invasive Intubation

The standard surgical procedure for inducing myocardial infarction (MI) in rat models via left anterior descending (LAD) coronary artery ligation typically requires invasive endotracheal intubation. While recent techniques have avoided intubation, they necessitate completing the ligation within a critically short period of less than five minutes. In this study, we developed an improved, simple and safe mask ventilation technique to extend this crucial timeframe.

Male Sprague-Dawley rats (6-8 weeks old) were anesthetized with isoflurane and ventilated using a custom size syringe mask. A high-viscosity ultrasound gel was used to create an airtight seal and prevent air leaks. Ventilation pressure was maintained between 8-12 cmH₂O. The LAD was ligated 1-2 mm distal to the left atrial appendage. A sham control group underwent the same procedure without LAD ligation. Post-operative cardiac function was serially assessed by echocardiography. Histological analysis was performed using hematoxylin and eosin (H&E) staining, and infarct size was quantified with Van Gieson's staining.

The MI group demonstrated a significant reduction in ejection fraction one week after surgery. The average infarct size was 27.1±3.45% in the MI group. Post-operative mortality was comparable between the MI and sham control groups.

This improved mask ventilation technique provides a simple and effective method for inducing reproducible MI in rats. It allows a substantially longer procedural time duration (~10 min) for careful and effective LAD ligation intervention and, eliminating the need for complex endotracheal intubation while maintaining a high survival rate.