Carbon monoxide poisoning is the most common cause of poisoning in the United States, sending about 40,000 people to the emergency room each year.

In a new study, researchers have discovered that severe carbon monoxide poisoning affects the body in ways no one fully realized until now.

Carbon monoxide is found in combustion fumes, such as those produced by cars and trucks, small gasoline engines, stoves, lanterns, burning charcoal and wood, and gas ranges and heating systems, according to the National Center for Environmental Health. It can build up in enclosed spaces, poisoning people and animals.

"Carbon monoxide attaches to the molecule in the blood that carries oxygen and it attaches instead of oxygen," said Dr. Cheryl Adkinson, an emergency room doctor at Hennepin County Medical Center in Minneapolis. "So somebody who had carbon monoxide poisoning is loaded up with carbon monoxide instead of oxygen."

This makes people feel light-headed or nauseous, and may make them pass out. But according to a new study, in patients with severe poisoning, carbon monoxide can also damage the heart.

Dr. Timothy Henry and colleagues at the Minneapolis Heart Institute Foundation were among those who authored the study, which was based on 230 patients with moderate to severe carbon monoxide poisoning. All of them had poisoning similar to that suffered by Randal McCloy, the only survivor of the West Virginia mine explosion this month. But most were exposed to the gas from faulty furnaces or fires.

Henry said the study results were surprising.

"Almost 40 percent of patients had heart damage related to the carbon monoxide poisoning, which was much higher than we expected," he said in a news release. "The carbon monoxide decreases availability of oxygen to the heart, which leads to heart damage."

Of the patients with heart damage, 38 percent died within about seven years after their carbon monoxide poisoning, mostly from heart problems. In comparison, 15 percent of the patients who did not have heart damage from the carbon monoxide poisoning died in that time frame.

"Most of us believed that since this was a one-time exposure to carbon monoxide, that if you were going to have problems you'd have them right away," Henry said. "And I think the key result of this finding is that that effect of carbon monoxide poisoning has effects not only today, but consequences down the line."

The study authors said the heart damage was worse in in older people with carbon monoxide poisoning. But a significant number of severe carbon monoxide poisoning patients who suffered heart damage were relatively young and had no previous heart problems.

Henry said doctors should check patients with severe carbon monoxide poisoning for heart damage, and in some cases, give the patients medicines to protect against heart problems in the future.

But Henry said the best way to prevent this kind of heart damage is to prevent carbon monoxide poisoning in the first place. A carbon monoxide detector in your home might help.

• Study Abstract