Transmyocardial Laser Revascularization Technique

Updated: Sep 27, 2017
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Brett C Sheridan, MD, FACS  more...
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Technique

Approach Considerations

Transmyocardial laser revascularization (TMLR) is based on the use of a high-powered carbon dioxide or other laser that interjects a strong energy pulse into the left ventricle, vaporizing the ventricular muscle and creating a transmural channel with a 1-mm diameter. The procedure can be used to create channels along the free left ventricular wall but not the septum. These channels are placed 1 cm apart in the ischemic myocardium. TMLR is performed to improve myocardial oxygenation, eliminate or reduce angina, and improve the patient's cardiovascular function.

The carbon dioxide laser is triggered to the electrocardiogram (ECG) to prevent arrhythmias (ventricular tachycardia). Cardiopulmonary bypass (CPB) is not required, and the patient is not heparinized. TMLR is a less invasive procedure, and it is appropriate for minimally invasive surgical incisions. Blood transfusions are rarely required, and recovery appears to be faster and less traumatic.

Clinical trials are investigating the benefits of TMLR compared with continued medical management for patients with angina who are not candidates for either percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG). To date, studies of TMLR have shown marked decreases in angina and improved functional status for patients with chronic angina.

The precise physiologic mechanism for the efficacy of TMLR is not thoroughly understood. Initially, blood was presumed to flow to the intraventricular chambers through the newly created channels. Today, it is unclear whether this is the exact mechanism by which myocardial blood flow is improved. One theory, albeit an unproven one, is that angiogenesis (growth of new blood vessels) may occur in response to the myocardial tissue injury caused by the laser energy; this may be the process that eventually leads to improved myocardial oxygenation.

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Use of Laser to Create Transmural Channels in Left Ventricle

The heart is approached via an anterolateral thoracotomy through the fifth and sixth intercostal spaces, and the pericardium is opened. Because most of these patients have had prior surgery, all dense adhesions must be carefully excised. In Europe, the thoracoscopic approach has been used in some patients who have not had previous operations.

The energy level for the laser is usually set at 15-60 J, corresponding to a pulse duration of 20-50 ms. The laser probe is placed in contact with the epicardium and fired, thereby vaporizing the myocardium in its path and creating a 1-mm wide channel that extends from the surface of the heart to the ventricular cavity. (See the images below)

Laser probe activated into the left ventricular wa Laser probe activated into the left ventricular wall creating a channel.
Laser probe is held on to the surface of the heart Laser probe is held on to the surface of the heart and activated to create channels.
Channels created by transmyocardial laser revascul Channels created by transmyocardial laser revascularization. The bubbles are created and can be visualized on echocardiography.

TMLR can be performed with a carbon dioxide laser or a holmium:yttrium-aluminum-garnet (YAG) laser. Carbon dioxide lasers can deliver up to 1000 W of energy through the myocardium. ECG electrodes are used to synchronize the pulsed carbon dioxide laser to fire with the R wave (corresponding to end diastole), thus minimizing the risk of ventricular arrhythmias. Transesophageal echocardiography (TEE) is used to confirm channel creation when transmural penetration is successful. On the TEE image, steam or bubbles are visualized.

The holmium:YAG laser transmits energy through optical fibers. Because the energy is more readily dissipated, three or four firings are usually required to pass through the entire myocardium. Regardless of the type of laser used, the laser energy vaporizes the myocardial tissue. One channel is created for approximately every 1 cm2 of ischemic myocardium; thus, a total of 20-40 channels are usually required.

Bleeding from the epicardial surface stops quickly, though local pressure or a suture may occasionally be required to achieve hemostasis. Once the desired number of channels has been created and hemostasis obtained, chest tubes are placed in the pericardial cavity and the incision is closed. An intraoperative TEE study is performed to exclude any injury to the mitral valve apparatus or the septum.

After 20-40 channels are drilled, the pericardium is loosely reapproximated. The chest is then closed in the usual fashion for a small thoracotomy.

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Postoperative Care

Postoperative care is extremely critical, particularly in regard to the maintenance of the appropriate perfusion pressure in the patient's coronary arterial system.

Patients who undergo TMLR are treated in the same manner as patients undergoing any open heart surgery procedure. After TMLR, all patients are transferred to the intensive care unit (ICU) and weaned off the respirator. Postoperative hemodynamics are monitored, and pressor drips are tapered accordingly. The average stay in the ICU is generally 1 day, after which patients are transferred to a monitored floor bed.

Because of the limited incision, shortened procedure, and nonuse of the CPB machine, most patients recuperate rapidly. The average stay in the hospital is approximately 2-3 days. The hospital stay is extended for patients who develop supraventricular arrhythmias, which must be controlled prior to discharge.

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Complications

In more than 1500 patients, intraoperative analysis has documented little morbidity. During the postoperative period, occasional supraventricular tachycardia, pleural effusions, and incisional pain from the thoracotomy have been observed. Because perfusion pressure determines perfusion of the collateral coronary circulation, maintaining adequate perfusion pressure until the patient has recovered completely is important. Hypotension must be avoided, and myocardial support with the use of intra-aortic balloon pumping is sometimes required.

Postoperative myocardial infarctions have been reported and are associated with a mortality of 8-10%. Mortality also appears to be correlated with the left ventricular ejection fraction in all the national studies, with highest early and late mortality in patients with worse left ventricular function.

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