Definition & Overview
Transmyocardial laser revascularisation (TMLR) by thoracotomy is a novel method of treating patients with coronary heart diseases. It uses carbon dioxide laser to create a channel in the muscle in the left ventricle. The goal of the procedure is to grow new coronary arteries to replace the damaged ones. TMLR by thoracotomy, which involves creating an incision in the chest wall, is not the first line of treatment for coronary heart diseases. It is only considered when conservative treatments have proven to be unsuccessful or when the patient remains to be symptomatic.
Coronary artery diseases (CAD) are medical conditions where the coronary arteries of the heart are blocked by a waxy substance called plaque. Coronary arteries are highly essential because they supply the heart with oxygenated blood to keep it functioning properly. When these coronary arteries are blocked by plaque, the condition is referred to as atherosclerosis.
The build-up of plaque around the lining of the arteries happens over time. Plaque causes the blood vessels to narrow and restrict the flow of blood to the heart. They can also harden and eventually break open. When they break open or rupture, they get stuck in other areas of the coronary arteries creating a blood clot.
The development of blood clot in the coronary arteries deprives the heart with oxygen that it needs to survive. If normal blood flow is not immediately restored, some of the heart muscles can die and the patient can eventually suffer a heart attack.
Untreated and recurrent coronary artery disease can weaken the heart muscle. Over time, the patient may develop arrhythmias or experience heart failure, where the heart loses its full capacity to pump enough blood.
Who Should Undergo and Expected Results?
The medical community has no clear indications for transmyocardial laser revascularisation but offers guidelines on its use. Generally, it is indicated for patients who do not respond well to initial therapy or those who do not qualify for existing medical procedures to treat CAD. This is particularly true for patients with angina pectoris or a coronary artery structure that is not suitable for bypass grafting or angioplasty. Angina pectoris is a condition marked by severe chest pain that spreads to other parts of the body such as the shoulders, neck, and arms.
Before the procedure, a myocardial perfusion scan is performed. TMLR is considered if the examination shows that the part of the heart being examined has reversible ischemia. This means that inadequate blood supply can still be reversed and the heart’s function can still be restored.
Surgeons also check on the patient’s left ventricular ejection fractions. If it is above 20%, the patient is considered a good candidate for TMLR. On the other hand, patients showing heart tissue necrosis or scarring are not suitable candidates for the procedure.
Clinical studies suggest that most patients who underwent TMLR experienced improvement on their chest pain (angina pectoris). TMLR is a good alternative for select candidates because it eliminates the need for other invasive procedure such as coronary artery bypass or the surgical creation of secondary channel when the main connection is blocked.
How is the Procedure Performed?
Transmyocardial laser revascularisation introduces a laser or high-powered carbon dioxide into the heart’s left ventricle. The goal here is to vaporise the damaged muscle tissues and create a transmural passage that is about 1-mm in diameter. This creates multiple passageways or channels between the myocardium and the left ventricular cavity. The left ventricle is one of the two largest chambers of the heart.
The operation makes use of left thoracotomy (a surgical incision in the chest wall) and performed in conjunction with coronary artery bypass grafting. This done by removing a part of a healthy vein or artery from other parts of the body. It is then connected to the necrotic coronary artery in a way that it bypasses the damaged portion of the coronary artery so that the blood can flow to the heart. The process creates a whole new pathway for the heart to receive the much-needed oxygen-rich blood.
The success of the procedure depends on the skills of the surgeon and the availability of healthy veins or arteries in the patient.
Possible Risks and Complications
Transmyocardial laser revascularisation by thoracotomy is highly invasive. Patients who undergo the procedure face the risk of dying particularly if they have other existing medical conditions and if they were already very ill before the surgery. This particular risk also increases with age.
Other factors also include ejection fraction, which measures the efficiency of the heart in pumping blood to the tissues of the body. It also tracks heart failure. For patients with an ejection fraction that is greater than 30% with manageable angina, the risk is minimal and they have better chances of surviving the procedure with fewer complications.
The mortality rate for this procedure is about 7-10%. This is the reason why it is very important to check for muscle scarring in the heart or any signs of necrosis (tissue death) prior to surgery. This is because it increases the risk of mortality during and after the procedure.
National Heart, Lung, and Blood Institute; “What Is Coronary Heart Disease” http://www.nhlbi.nih.gov/health/health-topics/topics/cad
US National Library of Medicine National Institutes of Health; “Transmyocardial laser revascularization”; https://www.ncbi.nlm.nih.gov/pubmed/7488780
Shabir Bhimji, MD, PhD Cardiothoracic and Vascular Surgeon; “Transmyocardial Laser Revascularization”; http://emedicine.medscape.com/article/428355-overview?pa=J1GR3EA2hwzrFQFyV1gzOkjy6aFIoSbBk758AmcYIApW1JxClciP2wJPXE8Rf5ewZo2BaCdE%2FtfcwsHojpeYovFDqoONiUtlOtdX6maZcRI%3D