CO2 laser for TMR wins FDA approval

Device safe - but choose patients carefully

A new carbon dioxide laser system for use in transmyocardial revascularization (TMR) procedures is now available for commercial use. The device was approved late in August by the Food and Drug Administration (FDA) for use in no-option patients - those whose severe stable angina and coronary artery disease cannot be controlled by other treatments, including medication, angioplasty, or bypass surgery. Typically those patients - estimated at 80,000 diagnosed each year - lead extremely restricted lives. The approved laser, called the Heart Laser System, is manufactured by PLC Medical Systems of Franklin, MA, and costs $400,000. The TMR procedure itself costs in the range of $20,000 to $40,000.

"Although this is not a life-saving procedure, it can provide significant relief of severe angina and improve the quality of life for a select group of patients for whom there is currently no effective treatment," said FDA Acting Commissioner Michael A. Friedman, MD, in a Department of Health and Human Services statement. Candidates are frequently taking maximal drug therapy, including nitroglycerin and beta or calcium channel blockers, and still not improving.

Allan Lansing, MD, director of the Heart Institute at Audubon Regional Medical Center in Louisville, KY, claims to be the only surgeon in the United States who has used both the carbon dioxide laser and the holmium:YAG laser system for TMR. He's been doing TMR for four and a half years.

"I've handled over 300 TMR procedures with laser systems," he tells Cost Management in Cardiac Care. "TMR costs less than half of what a coronary bypass would cost." The cardiac surgeon says that the procedure is "much simpler than a bypass, and the carbon dioxide machine itself is easy to use. The critical factor is having the experience to select patients who are likely to do well and who will come through the procedure well."

TMR patient costs typically average $25,000; charges for bypass surgery typically average $40,000; and angioplasty costs about $16,000 and typically must be repeated. Angioplasty with a stent can cost $20,000, and this too sometimes must be repeated. Clinical trials indicate that hospitalization for angina - approximately $3,000 per visit - can be reduced by 80% after TMR.

Average hospitalization for the laser TMR is five to seven days. Recovery is quicker and less traumatic than that following bypass surgery. Typically, no transfusion is needed.

Synchronization key to CO2 success

The principal attribute of the carbon dioxide system is its synchronization capability. By creating channels between heartbeats, the TMR can be performed on the beating heart, eliminating the need to stop the heart and place the patient on a heart lung machine, which can cause complications. In general, a laser's pinpoint accuracy causes little collateral damage and its intense heat promptly seals blood vessels.

Lansing has used and conducted clinical studies with both the carbon dioxide and the holmium:YAG laser systems. "In my experience," he says, "the carbon dioxide system gives better increase in blood supply and better relief of angina as compared to the YAG system."

The TMR procedure takes about two hours during which time surgeons make a four-inch left thoracotomy, insert the computer-synchronized laser, and burn up to 40 1-mm-sized channels about 1 cm apart through the damaged myocardium into the left ventricle of the beating heart. When the ventricle is filled with blood - is relatively still and unresponsive to stimuli - the laser is synchronized with the heartbeat and fires. This prevents damage to other tissues in the heart, because the blood acts as a backstop for the laser energy. The procedure is thought to reduce the risk of arrhythmia seen in TMR systems that are not synchronized.

The outer layers heal immediately, but the beating heart forces interior channels to stay open. Clinical studies have demonstrated that the creation of those channels allows oxygen-rich blood to flow into the heart muscle despite blocked arteries. The perception of pain may be reduced as well.

Hospital admissions fell

In studies, 72% of angina patients treated with the laser experienced significant pain reduction and were still experiencing this relief one year later.1 In addition, there was a significant decrease in hospital admissions for angina. In the year following the study, the patients receiving laser TMR had an average admission rate of 0.6 compared to 4.0 for those on medical therapy. By contrast, 13% of the patients treated with medication alone reported the same relief from angina. Laser TMR has resulted in a decrease of two or more angina classes in nearly 75% of study patients and elimination of all angina in one-third.

Investigators concluded that the TMR with laser reduces ischemic wall motion abnormalities and improves stress-induced tolerance during dobutamine echocardiography.

The typical study participant had already had at least one bypass surgery, and another would have posed a high risk. Study patients were not expected to benefit from angioplasty.

Laser TMR's risky, but CO2 tops others

Risks from the laser treatment include irregular heartbeat (10% of patients), stroke, and early death (within a month of the operation in 3% of patients). Another risk is that laser could accidentally fire into heart valves. Studies show that the treatment has no effect on the progression of coronary artery disease, and after one year, the mortality rate was found to be similar among patients who had received the laser treatment and those who had not.

Surgeons from the Texas Heart Institute in Houston presented data at a TMR symposium held in conjunction with the European Association of Thoracic Surgeons in Prague that concluded that the carbon dioxide system is the safest way to perform TMR. The investigators showed that the carbon dioxide laser has high pulse energy and creates transmural channels with a single pulse synchronized to a beating heart. The holmium:YAG and excimer lasers, utilizing low pulse energy, need to fire multiple pulses over multiple cardiac cycles in order to drill a single channel.

More than 30 hospitals currently perform TMR, among them the Texas Heart Institute at St. Luke's Episcopal Medical Center, Brigham and Women's in Boston, the Cleveland Clinic Foundation, and Rush Presbyterian-St. Luke's Medical Center in Chicago. The FDA has asked the carbon dioxide laser manufacturer to gather more information on mortality associated with the procedure and on its long-term benefits.

Reference

1. Donovan CL, Landolfo KP, Lowe JE, et al. Improvement in inducible ischemia during dobutamine stress echocardiography after transmyocardial laser revascularization in patients with refractory angina pectoris. J Am Coll Cardiol 1997;30:607-612.