Monday, July 6, 2015

Lifesaving Stents Get a Closer Look


Millions of patients have had stents-small wire cages - inserted in their coronary arteries to prop them open. And many are convinced the devices are protecting them from heart attacks. After all, a partly blocked artery is now cleared, and the pain in a heart muscle starved of blood often vanishes once the artery is open again.

But while stents unquestionably save lives of patients in the throes of a heart attack or a threatened heart attack, there is no convincing evidence that stents reduce heart attack risk for people suffering from the chest pains known as stable angina. These are people who feel tightness or discomfort walking up a hill, for example, because a partly blocked coronary artery is depriving their heart of blood. And there is a reasonable argument that drugs-cholesterol- lowering statins in particular-might be just as good at reducing such pain.

Now, the National Heart, Lung and Blood Institute is trying to find out whether stents do in fact prevent heart attacks. The answer could change the standard of care for patients who receive a new diagnosis heart disease.

The typical treatment for angina is to thread a catheter up from a blood vessel in the groin to the heart, squirt in a dye that allows a cardiologist to see blockages on X-ray, and then insert a stent in the blocked areas. Stents are safe but expensive; in the United States, they generally cost more than $10,000. And stents are not always a permanent solution to chest pain.

Stents were introduced in the 1990s, and because they relieved pain and were far less invasive than bypass surgery, they became the treatment of choice. Doctors and patients started to believe they also saved lives in stable patients.

“The thought was, better to go in and open it up,” said Dr. Harmony R. Reynolds, a cardiologist at NYU Langone Medical Center in New York and a principal investigator in the study.” But now meds have gotten so good that it is not clear surgery adds anything for stable patients.”

Researchers tried to get an answer with a big study in 2007. But many cardiologists did not believe its conclusion that stents failed to prevent heart attacks and deaths. Skeptics said most patients in the study were at such low risk that it did not matter which treatment they received. They were certain to do well, so the study proved nothing about whether stents worked.

Because of the doubts about that study and ingrained habits, medical practice was largely unchanged by its findings. A recent study, which analyzed recorded conversations between cardiologists and patients with stable angina, found that 75 percent of the cardiologists recommended stents and when they did, their patients almost always complied. And, the study found, on the rare occasion when the cardiologists presented both stents and medical treatment as options, none of the patients chose stenting.

The new study aims to avoid the methodological flaw in the 2007 study. Patients are not given angiograms, the test in which dye is injected into the coronary arteries, before being assigned a treatment. Instead, they are accepted on the basis of noninvasive tests that indicate blocked arteries and high risk of a heart attack. Their doctors know only that an artery is blocked-not which or how much-so they are not able to pluck out patients they believe need stents and prevent them from entering the trial.

Underlying the debate about the utility of stents is an uncertainty about how and why heart attacks occur. For years, the common notion was they were caused by a plumbing problem. In this view, plaque-pimplelike lumps-partly blocked a coronary artery and grew until no blood could get through, and a stent was needed to open an artery before it closed completely.

But a leading hypothesis says there is no predicting where a heart attack will originate. It could start anywhere there is plaque, even if the plaque is not obstructing the flow of blood in an artery. Unpredictably, a piece of plaque can burst open. Blood starts to clot on the injured area. Soon, the blood clot clogs the artery. The result is a heart attack. Certain plaques, with thin walls and bursting with fat-filled white blood cells, are prone to rupture. A study published in 2011 found only a third of heart attacks originated in plaques that were blocking at least half of an artery, as seen on an angiogram. The rest began with the rupture of plagues that appeared to be no problem.

According to this view of how and why heart attacks happen, the partly blocked area visible in an angiogram is no more likely to be the site of a heart attack than any other with plaque. But statins could work because they change the nature of plaques, making them less likely to rupture.

Although stents relieve chest pain, medical therapy can, too, though it may take months.

The issue potentially affects many heart patients. “Half the people over 65 have blockages,” said Dr. Gregg W. Stone of Columbia University in New York.

And once a stress test or an angiogram reveals a blockage, it can be hard to ignore it.

“People believe that if they have a blockage, they have to fix it mechanically,” said Dr.Judith S. Hochman, a cardiologist at NYU Langone and chairwoman of the study. “It seems logical, but in medicine, many things that seem logical are not true.” 

Taken from TODAY Saturday Edition, The New York Times International Daily, July 4, 2015