Transmyocardial Revascularization (TMR) is a procedure used to relieve severe angina or chest pain in very ill patients who aren’t candidates for bypass surgery or angioplasty. In this procedure, a surgeon makes an incision on the left breast to expose the heart. Then, using a laser, the surgeon drills a series of holes that are from 20 to 40 mm wide (about the size of a pin head) from the outside of the heart into the heart’s pumping chamber. In some patients TMR is combined with bypass surgery. How TMR reduces angina still isn’t fully understood. The laser may stimulate new blood vessels to grow, called angiogenesis or it may destroy nerve fibers to the heart, making patients unable to feel their chest pain.