Laser Treatment Reduces Scarring After Heart Attack

Low-energy laser irradiation has been shown to reduce biological "overreaction" to trauma in cell cultures and animal studies, but this study is among the first to explore its effect on alleviating some of the damaging effects of heart attacks. The results of the study were published in Circulation (January 16, 2001).

Other studies have focused on the use of drugs, growth factors and various intervention strategies in reducing myocardial infarct size and improvement of heart function after a heart attack. But low-energy laser irradiation seems to lessen the severity of a heart attack by increasing mitochondrial respiration and ATP, the major source for cellular energy production. The increase of both biological processes improves the cellular response to wounds, promoting healing and muscle regeneration after injury.

Mitochondria are rod-like structures in the cytoplasm, the substance of the body of the cell in which most cell activities occur. Mitochondria serve as the center of cellular enzyme activity.

In the study, researchers induced heart attacks in 50 dogs and 26 rats, half of whom received direct laser irradiation on the heart muscle after the chest was opened. Five to six weeks later, the animals were euthanized and the size of their infarcts, the areas of tissue death caused by a lack of oxygen, were examined. The laser treatment significantly lowered mortality from 30 percent to just 6.5 percent in the dogs after the induction of myocardial infarction.

"Our study demonstrated that the mortality rate was much lower in dogs treated with low-energy laser following myocardial infarction, compared with the control group," said Technion researcher Gal Hayam. "Pathologic examinations also revealed that laser treatment after myocardial infarction significantly decreased the size of the scar, or non-contracting tissue." The low-energy laser procedure reduced scarring and infarct size by more than fifty percent. Biological healing processes were elevated in dogs that received low-energy laser irradiation, compared with animals in the control group.

The results indicate that low-energy irradiation reduces the formation of scar tissue after heart attack, noted Prof. Uri Oron of Tel Aviv University, who led the study. "The possible beneficial and cardioprotective effects of the laser irradiation were quite evident."

In rats, the ATP content was 7.6 times higher in laser irradiated animals than among the control groups, and only 14 percent of the mitochondria in the ischemic zone, where there is a lack of oxygen, were found damaged four hours after the heart attack, compared to 36 percent of rats that did not receive laser treatment.

The injured laser-irradiated cells may have a much slower rate of degeneration because the procedure reduces the amount of damage to the mitochondria and elevates the formation of molecules that contribute to better survival of the heart cells in the ischemic zone.

The researchers’ observations indicate that delivery of laser energy to the heart may have an important beneficial effect on patients after acute myocardial infarction and other ischemic heart conditions that are not accessible to current revascularization procedures. "The use of low-energy laser irradiation has no known deleterious effect in humans, so it can be postulated that such irradiation is probably safe," Prof. Oron said.