Transmyocardial revascularization (TMR) is a laser surgery that opens tiny new pathways within the heart muscle. It is a procedure to treat the symptoms of angina in patients who cannot withstand more conventional treatments such as bypass surgery or balloon angioplasty, or in patients who have received maximum benefit from other therapies but are still experiencing symptoms of heart disease.

Although great strides have been made in treating coronary artery disease, there is little to offer people who continued to suffer from chronic chest pain, pressure or discomfort despite medical intervention. Some of these people may be too weak or too ill to undergo surgery. Others have already had or may not respond to traditional treatments such as bypass surgery or angioplasty with coronary stenting. In many cases, these patients were left with debilitating pain and little ability to treat it. Studies have also shown that such patients have worse outcomes than patients who no longer experience symptoms after treatment. One such study showed that about 25 percent of patients who still experienced symptoms after therapy experienced a heart attack within one year of treatment. 

TMR may be recommended for these patients. TMR has been shown to reduce symptoms and increase the patient’s capacity for exercise. The exact mechanism behind this improvement is still unknown. Some believe that this strategy offers less trauma for the patient, a shorter hospital stay and a lower risk of serious complications. Other research studies have cast doubt on TMR’s effectiveness.

As with any surgical procedure, there is the risk of side effects with TMR, including heart attack and abnormal heart rhythms. Surgeons have also developed an alternative catheter-based procedure called percutaneous transmyocardial laser revascularization. This procedure is performed with a catheter and does not require major surgery. Early studies have shown it is about as effective as the traditional method. TMR is a treatment for symptoms and not a cure for coronary artery disease. Healthy lifestyle choices are critical after TMR to maintain any improvements from the procedure.

Transmyocardial revascularization (TMR) is a therapeutic procedure that uses a laser beam to create small holes in the heart muscle (myocardium) of the left ventricle. TMR may be recommended for patients with chest pain (angina) that does not respond to medication or who are ineligible for other treatments such as coronary artery bypass graft (CABG) surgery. It may also be used as an adjunct to minimally invasive CABG surgery to increase the procedure's effectiveness. Studies have shown that TMR reduces the severity of symptoms and increases a patient’s capacity for exercise. However, TMR is not a cure for coronary artery disease, and there is no evidence that it can offer people a longer life.

There are a number of reasons patients may be referred for TMR instead of bypass surgery or balloon angioplasty. They include:

• There are too many individual blockages in the coronary arteries for either balloon angioplasty or bypass surgery to treat effectively.
  
  
• The patient’s arteries are too small to accommodate a catheter, which is necessary in order to perform a balloon angioplasty.
  
  
• The existing coronary artery disease is too advanced and the arteries cannot be repaired.

In some cases, TMR is also recommended as an adjunct therapy to bypass surgery. This often happens when the coronary artery disease is widespread and one area of the heart cannot be bypassed for a variety of reasons.

It is not completely clear how TMR helps relieve angina.  The channels created by the procedure close, but TMR may stimulate angiogenesis, a natural process in which the body creates new blood vessels to improve blood flow. In addition, the procedure may destroy some nerve cells in heart tissue, which reduces the angina pain. Finally, the success of TMR may be due to a placebo effect – patients feel better simply because they received treatment.

A number of tests may be performed before transmyocardial revascularization (TMR). These tests will help the physician to determine the location and severity of the damage in the coronary arteries. The tests include:

• Medical history. Family medical matters can provide valuable insight into an individual’s future because many medical conditions, including heart disease, run in family. During a medical history, the physician will ask questions about the patient’s family medical history as well as personal medical history.
  
  
• Physical examination. A physical examination, or “physical,” allows the physician to inspect the body, looking for evident signs of heart disease or other illness.
  
  
• Electrocardiogram (EKG). This is a recording of the heart’s electrical activity as a graph on a moving strip of paper or video monitor. The highly sensitive electrocardiograph machine helps detect heart abnormalities, disease and damage by measuring the heart’s rhythms and electrical impulses.
  

  

• Echocardiogram. This test uses sound waves to visualize the structures and functions of the heart. A moving image of the patient’s beating heart is played on a video screen, where a physician can study and measure the heart’s thickness, size and function. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation) or narrowing (stenosis). During this test, a Doppler ultrasound may be used to evaluate cardiac blood flow.
  
  
• Stress test. A stress test may be ordered so the physician can assess the heart’s reaction under physical stress. During an exercise stress test, an electrocardiogram is performed while the patient exercises in a controlled manner on a treadmill or stationary bicycle at varied speeds and elevations. During a pharmacological stress test, a medication (e.g., dobutamine) is given to the patient that causes the heart to react as if it were under the physical stress of exercise, although the patient is actually at rest. Using either technique, the reaction of the heart under stress can be measured and evaluated.
  
  
• Coronary angiogram. In some cases, this minimally invasiveinvasive catheter-based test will need to be performed to verify the location and severity of blockages in the coronary arteries. The test uses a special dye administered through a catheter to visualize the coronary arteries.

Transmyocardial revascularization (TMR) surgery takes place in an operating room of a hospital. After the patient is put to sleep by general anesthesia, a small cut (incision) is made between the ribs on the person’s left side, revealing the left ventricle of the heart.

The surgeon can see the heart beating. The heart beats in two phases. In the first phase (diastole), the ventricle fills with blood as the heart wall thins. In the second phase (systole), the ventricle “beats,” pumping the blood as the heart wall thickens. Because of the risk of damaging the heart wall, the laser should only be fired during the second phase of the heartbeat when the heart wall is thickest. It should not be fired during diastole when the heart wall has thinned. Therefore, the laser is precisely timed by an electrocardiogram (EKG) to fire between beats.

The laser is inserted between the ribs, and a transesophageal echocardiogram allows the physician to see exactly where to guide the laser into the left ventricle. After the laser is in place, the surgeon uses it to create up to 40 pathways through the cardiac wall and into the left ventricle. Each tiny pathway is only 1 millimeter in diameter and about 1 centimeter apart from the next. The surgeon blocks the entrance to the pathways with gentle pressure from a gloved finger and the surface openings close by forming blood clots, leaving the new interior pathways open.

The laser is then removed, and the incision is closed with stitches (sutures). After the surgery is complete, the patient is taken to the cardiac care unit for observation. The entire surgery takes approximately 1 to 1.5 hours to perform.

A variation of this procedure is called percutaneous myocardial revascularization (PMR) in which the laser is delivered through an artery via a catheter until it arrives at the heart. This procedure is also known as percutaneous transmyocardial laser revascularization or PTMR, and has been shown to improve exercise tolerance and relief from angina pain.

Most patients stay in the hospital for about four to seven days following transmyocardial revascularization (TMR) surgery. This includes several days under observation in the cardiac care unit and the remainder in a less critical care room. Even after discharge, minimal activity is recommended for several weeks during the healing process. A physician will work with individuals to assess their progress and to determine a safe range of activity.

The main goal of the procedure is to reduce the symptoms associated with coronary artery disease and increase patients’ ability to exercise. Other potential benefits from a TMR include:

The American Heart Association estimates that 80 to 90 percent of patients show significant improvement after a TMR. However, it may take time for these benefits to be fully enjoyed. Recognizable improvement after a TMR may not appear for three months or more, and maximum effectiveness may not be realized until as much as one year following the procedure. Research has shown that after one year TMR typically results in a higher quality of life for the patient. It has a very low rate of mortality or serious complication that requires hospitalization.

TMR is not a cure for coronary artery disease but simply a procedure that helps to relieve a major symptom – angina. Ongoing high-risk activities such as smoking will continue to worsen existing heart problems and reverse the benefits afforded by this surgery. Therefore, individuals who have undergone a TMR are strongly urged to follow a strict preventive program of diet and exercise, and smokers are strongly urged to quit smoking.

The risk of complications is low, but all surgeries carry at least a small risk of complications. These complications could include:

There is a less invasive, catheter-based procedure for performing transmyocardial revascularization (TMR). In this procedure, a laser-tipped catheter is fed through the femoral artery in the groin and all the way to the heart. There, it can create the channels in the heart. By inserting the laser into the body via a catheter instead of an incision between the ribs, the following advantages are gained:

Researchers are also studying the use of needles to drill holes in the heart wall to have the same effect as either of the TMR procedures. In addition to these alternatives to TMR, there is also a noninvasive treatment for angina called enhanced external counterpulsation (EECP). The treatment involves air (pneumatic) cuffs that are wrapped around the legs at three places and inflated between heartbeats. The inflated cuffs gently compress the blood vessels in the leg, forcing blood back into the heart. Like TMR, this can help to relieve angina. However, it is not appropriate for people who have conditions such as:

• Unpredictable chest pain (unstable angina)
• Heart failure
• Major damage to the heart muscle
• Serious valvular heart diseases (e.g., aortic regurgitation)
• Atrial fibrillation or frequent extra heartbeats
• Uncontrolled high blood pressure (hypertension)
• Severe artery or vein disease in the legs
• Tendency to bleed excessively (including those with ulcers)
• Pregnancy

EECP is also not advised for people with pacemakers, implantable defibrillators or patients taking anticoagulants.

Ultimately, however, the use of TMR is limited by the increasing sophistication of both conventional coronary artery bypass graft surgery (CABG) and angioplasty/stent procedures. In recent years, these techniques have been refined and applied to ever-sicker and older patients, thus narrowing the pool of prospective patients that might have been recommended for TMR. As a result of these limitations, TMR is generally used today as an adjunct to CABG surgery for parts of the heart that are severely lacking oxygen-rich blood.

In the 1930s, investigators realized that there were also microscopic pathways within the heart’s interior in addition to the coronary arteries on the heart’s surface. Although this was the first time these pathways were discovered in humans, they were already known to be functioning in reptiles. For example, the hearts of alligators and snakes rely solely on these microscopic pathways for blood supply because they have no coronary arteries.

Inspired by this information, researchers considered how new pathways might be created within the human heart to increase blood flow. In the 1950s, one procedure attempted to open a new cardiac pathway by implanting the mammary artery inside the heart. Another procedure used needles to open pathways. Unfortunately, these attempts generally failed.

In the 1970s, investigators began to successfully create new pathways in animals’ hearts through the use of lasers. The procedure was then tested on human subjects, with preliminary data showing encouraging results. Initially, researchers assumed the benefits of TMR were due to the creation of new blood channels in the heart. However, later imaging studies showed that the new channels closed quickly, sometimes within an hour after the procedure. Also, the amount of blood in the heart after TMR is not greatly increased from the amount of blood before the procedure, so the explanation could not be increased blood flow to the heart. Thus, the actual mechanism of action for TMR’s benefits remains unknown.

Nevertheless, the procedure has clearly demonstrated its ability to reduce symptoms in patients suffering from chest pain. The U.S. Food and Drug Administration (FDA) has approved TMR for cases of severe angina where other therapies have not shown benefit. Hundreds of TMR procedures have now been performed around the United States and in Europe.

Preparing questions in advance can help patients have more meaningful discussions with their physicians about their condition. Patients may wish to ask their doctors the following questions related to transmyocardial revascularization (TMR):

1. Why can’t I have angioplasty for my angina?
   
   
2. Why do you recommend TMR for me?
   
   
3. If I have TMR once, will I have to repeat the procedure if the pain comes back?
   
   
4. Previous surgeries have not helped my pain. How will this procedure help if surgery has not?
   
   
5. I have had a heart attack. Does TMR present any risks for having another one?
   
   
6. Should I use medications for my angina instead of TMR?
   
   
7. Are there any lasting side effects after the TMR procedure?
   
   
8. How many TMR procedures have you performed?
   
   
9. What are the pros and cons of the surgical and catheter-based versions of TMR? Which is better for me?
   
   
10. Will I have any activity restrictions after the procedure?
    
    
11. Will having TMR at the same time as bypass surgery lengthen my hospital stay or cardiac rehabilitation? Will it affect my recovery in any way?