Written by Shabir
All you ever wanted to know
Despite advances in both medical and surgical management of coronary artery disease, there is still a large group of patients who remain symptomatic after extensive medical and surgical treatment regimens. Typically, these patients continue to have chest pain while on maximal medical therapy and most are at an extra ordinary risk for surgery. In the last decade, a technique of improving the blood supply to the heart has been the development of laser. This technique known as transmyocardial revascularization (TMR) is now being used in North America to treat individuals with end stage heart disease
What is TMR?
Over the past decade, a new technique of possible revascularization of the heart is the use of laser. Transmyocardial revascularization (TMR) is a technique where by a laser is used to pierce channels in the heart using CO2 as the energy source. These new channels are believed to bring blood from the ventricular cavity directly into the myocardium. The result is a heart that mimics a reptilian heart, in which approximately half of the myocardial blood supply comes from sinusoidal perfusion by the left ventricular cavity. TMR is performed in an effort to improve myocardial oxygenation, eliminate or to reduce angina, and to improve the patient’s cardiovascular function status.
How does TMR WORK?
The premise of TMR is based on the use of a high powered CO2 laser that generates high energy pulse in the heart muscle and creates channels. These channels somehow are thought to transmit more blood to the heart muscle
Are there any clinical trials about TMR?
Clinical trials over the past 5 years have investigated the benefits of TMR compared with continued medical management for patients with angina who are not candidates for either percutaneous coronary angioplasty or coronary artery bypass grafting (CABG). To date, the studies on TMR show marked decreases in angina with improved functional status for patients experiencing chronic angina.
How does TMR relieve angina?
This is still open to question and no one really knows. A few hypotheses are:
- creation of channels in the heart muscle (none have been found at autopsy)
- stimulate growth of new blood vessels
- the hot laser destroys the pain nerves and thus pain is not felt anymore
All these three theories have not been established as fact and the process where by TMR improves angina is unknown
Can TMR be done instead of open heart surgery or angioplasty?
NO, TMR is not first choice therapy and infact the treatment of last resort. TMR is not a replacement therapy for open heart surgery or angioplasty either.
Who is a candidate for TMR?
- In general, candidates for TMR are those who are not able to undergo open heart surgery or angioplasty
- Individuals with extensive coronary disease which can’t be treated with either open heart surgery or angioplasty
- Individuals who have already undergone open heart surgery and or angioplasty and can’t be helped anymore
- Individuals who have a heart transplant and develop coronary artery disease (and are unable to get another heart)
Who is not a candidate for TMR?
Even though TMR is not as invasive as open heart surgery, it definitely does have certain complications. Some individuals may be at very high risk for the procedure and these individuals are not candidates for TMR.
- Patients with infarcted (dead) or scared tissue are not candidates for TMR.
- The patient with a very poor heart function are not candidates for TMR.
- Individuals with unstable angina (continuous chest pain at even the slightest provocation)
- Patients with severe adhesions from prior coronary artery bypass surgery can have significant bleeding via a median sternotomy approach and thus, in these cases, a left anterior thoracotomy may be an alternative.
What preparations are required before TMR?
One should not think that TMR is a trivial procedure. It requires the same work up as any open heart procedure. Requirements before surgery include
- A complete history
- physical exam
- chest x ray
- preoperative nuclear scan to identify areas of the heart that may be ischemic but not dead
- other tests may include an echocardiogram, PET scan or cardiac MRI
After the tests, the doctor will determine if you are a candidate for TMR.
How is the Surgical Done?
You will be admitted and have nothing to eat the night before surgery. On the day of surgery, you will be taken to the OR and given general anesthesia. Once all the necessary lines and monitors are in place, the surgeon may elect to perform the procedure by opening up the middle of the chest bone or a small incision just below your left nipple. Since most patients have had prior surgery; all the dense adhesions must be carefully excised. In some patients in Europe who have not had previous operations, the thoracoscopic approach has been used.
After the heart is exposed, the laser probe is fired to the areas of the heart previously identified on a nuclear scan. The entire procedure is monitored with a small probe placed in the upper esophagus (TEE). On average about 20-35 small holes are created by the laser. Once the holes have been created, the bleeding is stopped and the chest is closed you will be monitored in the ICU.
TMR usually takes one to two hours. The procedure may last longer if it is combined with other heart procedures.
What is Postoperative Care?
All patients who undergo TMR are treated exactly like a patient undergoing any open heart surgery procedure. All patients are transferred to the intensive care unit and weaned off the respirator. You will be monitored exactly like any open heart surgery patient. The average stay in the ICU is generally one day and transferred to a monitored floor bed the next day. Because of the limited incision, shortened procedure and non usage of the cardiopulmonary bypass machine, the majority of patients recuperate rapidly. The average stay in the hospital is in the order of 2-3 days. Hospital stay is extended in those patients who develop supraventricular arrhythmias, which need to be controlled prior to discharge.
What are Short Term results of TMR
Numerous studies have reported on the use of TMR. The studies have shown
- decrease in anginal episodes
- better quality of life
- decreased use of anti anginal medications
- decreased hospital admissions
What do long term data reveal?
Recent long term studies have unequivocally demonstrated the superiority of TMR in decreasing angina. Five-year follow-up of prospectively randomized patient have shown that the anginal relief is significant. However, these studies are not uniform and a number of studies shown no benefit at 5 years.
Can CABG combined with TMR?
Over the last few years, it has become more evident that TMR may be more useful as a hybrid procedure when used in combination with CABG. Several randomized studies have shown that the combination of TMR and CABG has more clinical benefit than TMR or CABG alone. Again these results are not always seen by everyone.
Is there any follow up after TMR?
Yes, TMR is no longer an experimental procedure. Just like any open heart surgery patient, regular follow-up includes history, physical examination, evaluation of angina and quality of life. A series of tests including echocardiograms, thallium scans and exercise tolerance tests is obtained regularly.
How active can you be after TMR?
Your doctor will discuss specific activity guidelines tat are appropriate for you after your procedure. A supervised cardiac rehabilitation program is recommended to help guide your recovery and help you progress your activity level.
What are Complications of TMR?
In thousands of patients intraoperative analysis has documented little morbidity. In the postoperative period one may see:
- abnormal heart rhythms
- collection of fluid in the chest
- pain from the surgical incision
Postoperative myocardial infarctions have been reported and carry a mortality of 8-10%. Those with poor functioning hearts are at the highest risk of a heart attack.
What are advantages of TMR over open heart surgery?
For TMR, neither cardiopulmonary bypass (CPB) is used nor is the patient heparinized. It is a less invasive procedure, with a small chest incision and rarely requires blood transfusions. Therefore the recovery is quicker and less traumatic.
What lasers are used Alternative laser sources?
A number of different laser technologies have been developed while the studies with the CO2 laser are completing the FDA approved trials. The entire experience todate has been gained mainly with the CO2 laser. Other laser technologies are not coordinated with the ECG and therefore may not protect against the ventricular arrhythmias. Also, the other laser technologies are not produced with high energy so they do not protect against perichannel "burns" and other forms of tissue destruction around the channels.
What is Future?
Although coronary artery bypass surgery is effective in many patients, there are some patients who are not candidates for revascularization procedures. In the last few years, TMR has been initiating a significant interest in the treatment of otherwise surgically untreatable coronary artery disease. The results of several large clinical studies show marked improvements in angina that appears both instantaneously after TMR and is sustained. In most cases, there is a comparable improvement in exercise tolerance. The mechanism whereby TMR works still remains unknown.
Is TMR covered by insurance?
TMR is covered by most insurance companies. Ask your insurance company if you have coverage for this procedure.
PLC Medical Systems, Edwards Lifesciences*
Horvath KA, Aranki SF, Cohn LH, et al. Sustained Angina Relief 5 Years after Transmyocardial Revascularization with a CO2 Laser. Circulation 2001:104 (Suppl) I: 81-84.
Frazier OH, March RJ, Horvath KA, Transmyocardial Revascularization With A Carbon Dioxide Laser In Patients With End-Stage Coronary Artery Disease, New England Journal of Medicine, 1999, 341: 1021-1028.
Allen KB, Dowling RD, Fudge YL, et al. Comparison of transmyocardial revascularization with medical therapy in patients with refractory angina, New England Journal of Medicine, 1999, 341: 1029-36.
Allen KB, Dowling RD, DelRossi AJ, et al. Transmyocardial laser revascularization combined with coronary artery bypass grafting: a multicenter, blinded, prospective, randomized, controlled trial. J Thoracic Cardiovascular Surgery, 2000, 119: 540-9.
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