What is TMR?
Transmyocardial revascularization (TMR) is a surgical procedure that may be performed in people with stable angina (chest pain that occurs in a predictable manner, often triggered by exercise or stress) who do not find relief with medication. TMR is a “last resort” for relief of stable angina. It is used only when more conventional treatments, such as angioplasty or bypass surgery, are not possible. This can be the case for people whose heart disease has progressed to such a point that these treatments would not work (too many blockages in the arteries) or those who are too sick to undergo surgery.
There is no gender-specific information available on TMR. About 8,000 people underwent TMR from 1995 through 2003.1
See also: Chest Pain (Angina)
What is PMR?
PMR is very similar to TMR, except that it is a not a surgical procedure. A catheter is threaded into your heart through your groin, eliminating the need for your chest to be cut open.
How well do TMR and PMR work?
There are few studies on TMR and even fewer on PMR. Early studies of TMR and PMR suggested that these procedures did relieve chest pain, but it was not clear why or how. One theory to explain their benefit was that they might cause angiogenesis, the growth of small new blood vessels in the heart. Another was sympathetic denervation, destruction of nerves in the heart so that the patient couldn't feel chest pain. Recent studies indicate that, especially for PMR, the benefits may be due to a placebo effect – people feel better just because they have received treatment.
Most studies find that TMR is effective at relieving chest pain compared with medication alone.2-7 Angina is measured by class with Roman numerals from I to IV with IV being the worst. In most small studies, TMR improved angina by 2 classes, and some people were also able to exercise more. There have been no large randomized, placebo-controlled studies on TMR – the standard for determining the effectiveness of a treatment – because it would be unethical to subject people to a serious surgical procedure without giving any treatment.
Early small PMR studies that were not placebo-controlled found that it was also effective at reducing chest pain. However, in the year 2000, the results of the largest randomized, placebo-controlled trial of PMR strongly suggested that it was no better than a mock procedure.8 In the study, people were assigned to a high dose PMR group (where 20 to 25 channels were made), a low dose PMR group (where 10 to 15 channels were made), or a placebo group that underwent a mock procedure where no laser pulses were actually delivered. All of the people were blindfolded, wore headphones, and were heavily sedated so that they would not know whether or not they had actually received PMR. The PMR group had decreased chest pain, but so did the patients in the mock procedure group. Both groups had the same amount of pain relief, were better able to exercise, and reported a higher quality of life—despite the fact that the people in the placebo group received no actual therapy. This indicates that the reduction in chest pain that people experienced was really due to a placebo effect, meaning that they felt better only because they believed they had received a helpful treatment.