Transmyocardial Revascularization (TMR)

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.

During the procedure, a laser is used to create small holes (“channels”) in the heart muscle of the left ventricle, the chamber of the heart responsible for pumping blood throughout the body.

There is no gender-specific information available on TMR. About 8,000 people underwent TMR from 1995 through 2003.

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. 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. 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.

TMR – Who Should Have It

Who is a candidate for TMR and PMR?

TMR may be considered for people who suffer from chronic stable angina and do not respond to treatment with medication. It is performed only in people who cannot have the standard treatments for this condition: angioplasty or bypass surgery. Angioplasty and bypass surgery may not be possible if there are too many blockages in the arteries (the heart disease has progressed to such a stage that the arteries cannot be repaired by one of these treatments). Additionally, some people’s arteries are too small to fit the catheter used in angioplasty. In some cases, bypass surgery and TMR are performed at the same time if there are some blockages that can be treated with bypass surgery but others that can’t. If your physician has told you that there is nothing else that can be done to improve your chest pain, TMR may be an option. TMR may also be appropriate if you need a repeat bypass surgery or angioplasty but are at high risk for serious complications.

PMR is rarely performed, except in experimental trials, because it has not been shown to have the same benefits as TMR.

Who should not have TMR?

If you have chronic stable angina, but your pain is being relieved with medication or you are able to have angioplasty or bypass surgery, you should not have TMR. These other treatments are known to decrease chest pain and reduce the risk of future heart problems.

Certain factors have been found that increase a person’s risk for problems and dying after TMR. One study found that diabetes put people at a greater risk for a heart attack or dying from a heart-related cause shortly after the procedure. People who have peripheral vascular disease (disease in the blood vessels of the arms or legs) or had a previous bypass surgery have a higher risk of dying during or just after TMR.

TMR – The TMR Procedure

What does the TMR procedure entail?

The surgical site, near the left breast, will be shaved if necessary and an antibacterial solution will be applied to the chest. You will be given a sedative through an intravenous (IV) line, and hooked up to an electrocardiogram (ECG) so that your heart rate and blood pressure can be monitored. For this, small sticky patches with wires attached will be taped to your body.

General anesthesia is given through a breathing tube to make sure you are asleep for the entire procedure, and it will be constantly monitored by your anesthesiologist. A tube called a catheter will be inserted in your neck and threaded into a pulmonary artery so that your physicians can measure your heart function and the pressure in your heart and lungs. A urinary catheter is also inserted.

The surgeon will first make an incision on the left side of the chest to access the heart’s left ventricle. A special laser is then used to make 20 to 40 tiny channels about 1 millimeter wide (the size of the head of a pin) and about 1 centimeter apart in the heart muscle. The channels bleed for a few seconds but stop when the surgeon presses on them gently with a finger. This causes the tops of the channels to clot.

How long does the TMR procedure take?

The procedure takes between 1 and 2 hours.

What happens after the TMR procedure?

You will stay in the hospital for 4 to 7 days following TMR. Your physician will discuss with you which activities you are allowed to do after the procedure, but you will probably be told not to perform any strenuous activities. Often, chest pain symptoms get better right after TMR, but sometimes it can take 3 months or more for you to feel relief.

What does the PMR procedure entail?

During PMR, a laser-tipped catheter is inserted in the groin area into the femoral artery and threaded into the heart. The laser pulses are then delivered by the catheter, and anywhere from 8 to 30 channels are made. Chest incisions and general anesthesia are not necessary for PMR, which reduces recovery time and the chance of complications.

How long does the PMR procedure take?

The PMR procedure takes between 1 and 2 hours.

What are the risks of TMR?

The risks associated with TMR are low but, as with all surgeries, there is a small risk of complications. With TMR, these may include the return of chest pain, damage to a heart valve, heart failure, heart rhythm problems, damage to the larger blood vessels of the heart, low blood pressure, and heart attack. Also, the long-term effects of TMR are unknown. Because the majority of studies on TMR are small and not placebo-controlled, results often vary. The risk of dying after TMR is about 5%. About one-third to two-thirds of people experience problems within 30 days of surgery, but few have serious complications that require hospitalization, such as heart attack, heart failure, or unstable angina.

Is TMR ever performed at the same time as bypass surgery?

Yes. currently, two-thirds of TMR surgeries are performed along with bypass surgery. TMR plus bypass surgery is not an alternative to bypass surgery alone. The two procedures are used together when there are one or more areas of the heart that can be treated with bypass surgery and one or more areas that cannot. People who have TMR plus bypass surgery have less severe chest pain after 5 years than eligible patients who had bypass surgery alone.

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