Rats and mice exposed to carbon monoxide were more likely to successfully recover from angioplasties and aorta transplants, a new study claims. The researchers suspect the gas prevents the vessels from becoming blocked again right after surgery.
However, it may be some time before humans get the same carbon monoxide treatment.
"The trick is to find the optimal safe dose, and future studies have to focus on the concentration that will be required," says study co-author Dr. Augustine Choi, a professor of medicine at the University of Pittsburgh.
According to the American Heart Association, doctors perform an estimated 1 million angioplasties each year in the United States. Typically, the procedure involves inserting a catheter into an artery, maneuvering it to the site of the blockage, and expanding the artery by inflating a small balloon. If all goes well, the balloon will deflate but the artery will stay open, reducing the risk of heart attack by improving blood flow.
However, arteries become blocked again in about a third of patients, often requiring another angioplasty or a heart bypass operation. In some cases, the angioplasty itself contributes to the blockage by causing inflammation in the artery, Choi explains.
Researchers have previously shown that carbon monoxide can help prevent blood clots in mice. In the current study, reported in the Jan. 19 online edition of Nature Medicine, scientists at the University of Pittsburgh and Harvard Medical School administered the gas to rats and mice that received either angioplasties or aorta grafts.
The researchers found the blood vessels of the rodents were much more likely to stay clear if the animals were exposed to carbon monoxide before the surgeries. About an hour of exposure in a chamber seemed to do the trick, Choi says.
The gas seems to prevent inflammation from forming, Choi explains. The researchers plan to next test their treatment on pigs, whose circulatory systems are more similar to those in humans.
Choi acknowledges that tests on humans will raise safety concerns. Pollution has turned carbon monoxide into a common ingredient in the air people breathe, but the gas remains dangerous.
Carbon monoxide is perhaps best known as the key method for those who commit suicide by sitting in a car with the engine running and the garage doors closed. Catalytic converters have made cars safer, but the gas still unintentionally kills people who use malfunctioning heaters, says Judith Alsop, director of the Sacramento division of the California Poison Control System.
Carbon monoxide fumes from barbecues and hibachis can also kill if they are used inside without proper ventilation.
"If you're inhaling carbon monoxide, you aren't inhaling enough oxygen," Alsop says. "The two organs that need the most oxygen are your heart and brain, and they manifest the most injury."
Victims of carbon monoxide poisoning will feel dizzy, light-headed and weak at first, Alsop says. Other symptoms include headaches, nausea and vomiting.
Heart patients are especially susceptible to carbon monoxide poisoning because their bodies can't handle the stress, she says. Doctors treat the symptoms by administering oxygen.
Get statistics about angioplasties from the American Heart Association.