Echocardiography-guided Injection for Targeted and Reliable Intramyocardial Stem Cell Delivery in a Rat Model of Myocardial Infarction.

Echocardiography-guided intramyocardial injection (EGI) is a minimally invasive technique for delivering stem cell therapies in preclinical myocardial infarction (MI) models. Compared to traditional open-chest approaches, EGI offers improved clinical translatability, reduced invasiveness, and minimized physiological impact on the animal. While EGI is well established in murine models, its application in rats remains limited due to anatomical and technical challenges. In particular, thinning of the left ventricular anterior wall (LVAW) in infarcted and peri-infarct regions complicates safe and accurate myocardial delivery, as wall thickness can fall below the needle bevel size of commonly used 27 G or 28 G needles, increasing the risk of ventricular perforation or failed delivery. To address this limitation, we optimized a protocol for EGI in rat MI models using 29 G Spinocan needles. The smaller-diameter, longer needle enables precise targeting of thin myocardial tissue, minimizing damage and enhancing injection accuracy, independent of LVAW thickness. This technique is compatible with standard transthoracic echocardiography platforms and eliminates the need for thoracotomy, allowing longitudinal studies in the same animal. Our refined method enables robust, reproducible delivery of therapeutic agents into viable myocardium adjacent to the infarct zone, where regenerative therapies are most effective. By improving safety and targeting precision, this approach increases the translational relevance of preclinical cardiac research and supports the development of standardized protocols across laboratories.