Punching Holes In Heart Helps Angina Sufferers
Transmyocardial Revascularization New York, NY, Sept. 11, 1999 -- Using a laser to punch holes in the wall of the heart can help relieve angina in patients for whom no other treatments are available, according to a study published in the Sept. 11, 1999, issue of The Lancet. Although it remains a mystery why the technique works, the study is the most scientifically convincing demonstration yet of its benefits, according to Dr. Daniel Burkhoff, associate professor of medicine at Columbia University College of Physicians and Surgeons and lead author of the study.
"We believe that we have conducted the most rigorous trial possible of a surgical procedure of this kind," says Dr. Burkhoff. "The results of the study suggest that this therapy is a reasonable option for patients who are really suffering and who have no other option."
Dr. Burkhoff estimates that about 75,000 patients per year in the United States might benefit from the procedure, known as transmyocardial revascularization or TMR.
Angina, typically a dull, squeezing pain in the chest and left arm, arises from inadequate blood flow to the heart, usually caused by arteries clogged with cholesterol. Medications to reduce cholesterol and improve blood flow are generally the first option offered to patients. For patients who do not respond to medications, angioplasty and coronary artery bypass are commonly used to eliminate or get around constrictions in the vessels supplying blood to the heart. But angioplasty and coronary artery bypass do not work for patients whose blood vessels are constricted in many places. The new study confirms that TMR can help these patients.
The procedure was originally developed as an attempt to mimic blood flow in alligator hearts. In addition to blood vessels on the outside of the heart, alligators and other reptiles have deep channels in the heart wall that allow oxygenated blood inside the heart to reach the muscle. Surgeons punched tiny holes all the way through the heart muscles in humans to see if they could get more oxygenated blood to the heart muscle. The holes closed up and failed to nourish the heart muscle with blood from inside the heart's chambers.
"You can't fool Mother Nature into thinking humans are reptiles," says Dr. Burkhoff. But the procedure did seem to provide some benefit to angina patients. So, researchers continued to investigate it.
The Lancet paper reports results from a multicenter trial, known as the Angina Treatments - Lasers and Normal Therapies in Comparison (ATLANTIC) Study. In this study, 182 patients with severe angina and poor response to other therapies were randomly assigned to treatment with either TMR and medication or medication alone. Twelve months later, mortality among the TMR patients was 5.4 percent compared with 10.0 percent in the medication-only control group. TMR patients were able to exercise an average of 65 seconds longer than before the procedure, while control group patients exercised 46 seconds less. Angina, as reported by patients, had improved significantly in 61 percent of the TMR patients and only 11 percent in the control group. TMR patients also reported an improved quality of life.
The results are more conservative than some reports, but Dr. Burkhoff believes the study's scientific rigor makes them more reliable. Many previous studies have used angina alone as a primary measure of efficacy. But pain is a notoriously subjective experience, especially when measured by physicians who know that a patient received TMR. This study tried to reduce that bias by using blinded reviewers to assess the angina. It also used more objective measures of mortality and exercise tolerance. Several previous studies also allowed cross-overs; patients who did not benefit from medications alone were allowed to try TMR. Cross-overs compromise the quality of the control group. This study had no cross-overs.
It remains unclear why TMR works. The current study showed no additional blood supply to the heart muscle as recorded by thallium stress tests. But more sensitive measures of blood flow used in previous animal studies in Dr. Burkhoff's laboratory did show increased blood flow to the heart muscle. Dr. Burkhoff believes the inflammation and subsequent healing that occurs after the holes are burned into the heart may promote the growth of additional blood vessels.
The study was funded by the CardioGenesis Corporation.