TMR, short for transmyocardial laser revascularization, is a medical procedure where a doctor uses a laser to create openings in the heart to alleviate intense pain. This technique can be performed on both the exterior and interior of the heart. When done externally, a laser (such as a CO2 or holmium laser) is positioned near the heart's left ventricle. The laser then applies enough energy to form small channels from the outer (epicardial) to the inner (endocardial) layers of the heart, creating several tiny holes in the heart muscle (the myocardium). Recently, this procedure has been adapted to be performed in the cardiac catheterization lab, where the laser operates from the inside out.Angina results from insufficient oxygen supply to the heart muscle. The laser-created channels aim to enhance the oxygen supply to the heart muscle by providing direct access to the oxygen-rich blood from the left ventricle. However, these channels quickly close up as they fill with tissue. While TMR does not significantly improve heart function, it seems to reduce or eliminate pain in patients with severe angina, at least temporarily.Initially, this procedure was conducted through heart surgery, which had an overall mortality rate of about 5 percent. The primary risks include arrhythmias (irregular heartbeats) and tamponade, which occurs when excessive blood accumulates in the sac surrounding the heart, hindering its function. Data from three significant randomized trials, published in late 1999, indicated that transmyocardial revascularization (TMR), whether performed via open chest surgery or percutaneously, was more effective in relieving angina and improving exercise tolerance compared to the best available medical therapy.

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