(CNN) -- Stents, small metal scaffolding devices placed inside blood vessels around the heart, are used to treat conditions that result when arteries become narrow or blocked.
Former President Clinton underwent a procedure to place two stents in one of his coronary arteries Thursday after experiencing chest "discomfort," his foundation said.
A stent is very effective at reducing chest pain and treating a heart attack, said Dr. Clyde Yancy, president of the American Heart Association.
In 2004, Clinton underwent a quadruple bypass operation to free four blocked arteries. For someone who has a history of heart problems, heart attack is the first concern, Yancy said.
Putting two stents in one coronary artery suggests that the problem was that one of the bypass grafts completely closed, and doctors had to fix his regular artery in the heart, said Dr. Michael Lee, associate director of interventional cardiology research at the Ronald Reagan UCLA Medical Center. Another possibility is that the bypass graft itself was blocked, but this probably would have required only one stent, he said.
Dr. Jonathan Reiner of George Washington University, cardiologist for former Vice President Dick Cheney, said the symptoms sound typical of angina or ischemia, which happens when blood flow to the heart muscle is decreased by a blocked coronary artery.
"The president had new symptoms suggestive a blockage of one of his arteries or a blockage in one of his bypass grafts, which is probably more likely," he said.
After bypass surgery, bypass grafts don't always have an indefinite longevity, Reiner said. It's not uncommon for a bypass graft to have a problem years after surgery, he said.
Angina commonly causes pain behind the breast bone or slightly to the left of it, according to the National Institutes of Health.
The pain of a heart attack may be similar but more severe, the institute said. Sudden, severe pain in the chest and upper back can result from aortic dissection.
Pain in the center part of the chest could mean inflammation or infection in the tissue around the heart, a condition called pericarditis, the National Institutes of Health said.
Chest pain can also emanate from the lungs: for example, pneumonia, a blood clot in the lung and asthma, the National Institutes of Health said.
"But heart disease is clearly the first thing we think about whenever someone presents with chest pain, because that can be most dangerous and precipitous," Yancy said.
Clinton's spokesman described the symptoms that led him to seek treatment as "discomfort in his chest."
"That's the best word to use -- discomfort," Yancy said. "More times than not it really is discomfort -- a sense of fullness, tightness. It can be pain, but sometimes people in the lay community are confused because they're expecting pain per se and ignore the other symptoms which might be."
Dr. Allan Schwartz, who oversaw Clinton's care, said his patient had seen him after several days of "episodes of chest discomfort, brief in nature but repetitive."
There is nothing in the news to suggest that the former president had a heart attack, Reiner said.
Because of Clinton's history of heart disease and bypass surgery, chest pains would raise a lot of concern, said CNN Chief Medical Correspondent Dr. Sanjay Gupta. But anyone who has chest pains, especially older men, should go to the hospital even if they haven't had bypass surgery.
In Clinton's case, there was concern about not enough blood getting to the heart, which is why the stents are placed, Gupta said. That could be because coronary arteries closed down over time, and it could have been around the site of his bypass operation, Gupta said. The stents open up the arteries again to allow enough blood to get through.
The first line of treatment when someone presents with chest pain is medical therapy consisting of aspirin, blood thinners like heparin, or newer drugs and bed rest, Yancy said. About 90 percent of chest pain goes away with special monitoring, he said.
CNN's Leslie Wade contributed to this report.