Intraoperative Multiplane Transesophageal Echocardiography for Guiding Direct Myocardial Gene Transfer of Vascular Endothelial Growth Factor in Patients with Refractory Angina Pectoris

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Abstract
Gene transfer for therapeutic angiogenesis represents a novel treatment for patients with chronic angina refractory to standard medical therapy and not amenable to conventional revascularization. We sought to assess the role of intraoperative multiplane transesophageal echocardiography (MPTEE) in guiding injection of naked DNA encoding vascular endothelial growth factor (VEGF) into the left ventricular (LV) myocardium of patients with refractory angina. After exposing the LV myocardium via a limited lateral thoracotomy, each of 17 patients in this series received 4 separate injections of VEGF DNA into different myocardial sites. Initial injections in the first patient produced intracavitary microbubbles, indicating injection of DNA into the LV chamber. Subsequently, each injection was preceded by a test injection of agitated saline. The absence of microbubbles while visualizing the LV cavity during the test injection verified that the ensuing injection of DNA would not be inadvertently squandered in the LV chamber itself. Intracavitary LV microbubbles were observed by MPTEE in 13 of 64 (20.3%) saline test injections and in 8 of 16 (50.0%) patients in which saline test injection was used, leading to adjustments in needle position. MPTEE imaging detected a previously unknown large, apical left ventricular thrombus in one patient, thereby preventing inadvertent injection of VEGF DNA through the myocardium into the thrombus. Imaging during and after injection verified no deleterious impact on LV function. We conclude that MPTEE is a useful tool for ensuring that myocardial gene therapy performed by direct needle injection results in gene transfer to the LV myocardium.