To enhance the safety of transendocardial delivery and the efficacy of intramyocardial angiogenic gene expression, a visible, less invasive, targeted, high-efficiency gene delivery strategy was tested. Progress toward clinical approval of systemic administration of genes and microbubbles (MBs) has been limited. The feasibility of transendocardially delivering MBs as extracellular markers and gene carriers in conjunction with intracardiac ultrasound (US) treatment remains unknown. In a canine acute myocardial infarction (MI) model, a naked plasmid encoding 500 μg human hepatocyte growth factor (HGF) was delivered transendocardially to the myocardium via US/MB (HGF-US/MB), insonation (HGFUS), or alone (HGF alone). Control MI dogs received saline without US/MB (control group). During US/MB, intracardiac insonation was performed for 30 s with a 10-s pause, at 4.3-MHz, 1-W/cm(2), for 60 s at each site. Gene and MB distribution in the myocardium was visualized. Compared to the HGF alone group at 28 days, the HGF-US/MB group had an average 7.1-fold enhancement in gene expression (P < 0.01). Compared to the control group, there were 16% decreases in the ratio of left ventricle (LV) weight/body weight in the HGF-US/MB group and decreases in collagen volume fraction (CVF) of type I (33%) and type III (23%) collagen. Capillary density increased from 22.8 ± 6.3/mm(2) in the control group to 154.3 ± 42.9/mm(2) in the HGF-US/MB group (P < 0.01). This less invasive catheter-based US therapeutic procedure offers observable gene delivery with higher therapeutic efficiency, enhanced angiogenesis, and improved myocardial perfusion and ventricular function following MI.