) Coronary vessel occlusion leading to myocardial ischemia is one of the leading causes of morbidity and mortality in the Western hemisphere. Several methods have been developed to achieve revascularization of ischeniie regions of myocardium. Mechanical approaches include surgical bypass and balloon angioplasty to circumvent or open occluded vessels, and approaches such as transmyocardial laser revascularization (TMR) to directly enhance myocardial blood flow by the provision of new intramyocardial vascular channels. TMR, which has been shown to lead to significant anginal relief, was initially thought to create persistent laser-drilled vascular channels. It is now hypothesized that the beneficial results of TMR are associated with the induction of intraynyocardial angiogenesis in the context of a tissue bearing response. Proton beam radiation is based on the characteristic of proton beams to deposit energy at prescribed, adjustable tissue depths while minimizing exposure of overlying skin and superficial structures and sparing structures deep to the desired target tissue volume. The unique ability of proton beams to deposit specific doses of ionizing radiation to subsurface tissues suggests the possibility that proton beams specifically directed to myocardial tissues could induce a localized angiogenic response. This myocardial angiogenesis could supply blood flow capable of preserving myocardial function in the context of native arterial occlusion. This exploratory study will examine the feasibility of using external proton radiation to induce myocardial revascularization.
