MRI-guided myocardial cell therapy.

Abstract

Novel cell based therapies are being developed to treat ischemic heart disease. High local concentrations of agents will likely be necessary for biologic efficacy. Intracoronary artery infusion through patent arteries has been tried with variable success in several clinical trials (1,2). However, first-pass retention of cells is low when they are administered intra-arterially. Moreover, intra-arterial delivery requires patent inflow arteries, which often is not the case in severe chronic myocardial ischemia. Direct injection into the myocardium is attractive because it may accomplish high local delivery while reducing systemic exposure and toxicity. Catheter based injection methods are also attractive compared with open surgical injection by virtue of reduced invasiveness and attendant lower morbidity. X-ray guided catheter based endomyocardial delivery systems are widely available (3,4). Soft tissue contrast provided by contemporary x-ray fluoroscopy is poor. In order to visualize blood spaces, they must be filled with potentially toxic radiocontrast agents. Successful and spatially precise cell delivery to diseased myocardium is not assured, especially with regard to inadvertently overlapping injections. Electromechanical navigation (NOGA with Myostar injection catheter, Cordis-Webster) can be used to guide cell injections. It creates a 3dimensional roadmap by combining an electrical sensing catheter with a electromagnetic position sensor (5–8). This approach is elegant but may be limited because creating the roadmap is timeconsuming, and because the roadmap may misrepresent the current cardiac position based on patient, respiratory, and cardiac motion as well as changes in cardiac rhythm and loading conditions. Furthermore, this technique does not confirm successful cell injection. Even in experienced hands electromechanical mapping has only 80% sensitivity and specificity to distinguish between normal and infarcted myocardium in a non-transmural infarct (9). An ideal delivery system should be able to: