For people with heart disease, it’s been thought that inserting a stent was the best way to treat sudden chest pain during exercise. But a landmark study suggests that this invasive procedure might not be necessary, and instead, medication and lifestyle changes are enough.

The findings, presented Saturday at the American Heart Association's annual meeting in Philadelphia, could help guide millions of conversations between patients and their doctors when deciding which treatments are best.

"Probably the majority of patients, if you offered them a choice of just taking medicine or having a procedure, many will likely opt to just take medicines," said Dr. Glenn Levine, a professor of medicine at Baylor College of Medicine and the director of the cardiac care unit at the Michael E. DeBakey Medical Center in Houston. He was not involved in the new research.

The study focused on patients with what's called ischemic heart disease. That usually means that plaque has built up in the coronary arteries, which supply blood to the heart muscle, narrowing them and making it more difficult to pump blood.

That translates into chest pain or tightness — called angina — when those patients exercise or experience emotional stress, because their body is trying to pump more blood, but can’t do so effectively through such a restricted space.

When patients rest, though, the pain goes away. Doctors call that “stable angina.” It’s not a medical emergency, but does require an appointment with a doctor. According to the American Heart Association, stable angina accounts for 2.3 million such office visits in the United States every year.

During those exams, patients hop onto a treadmill or stationary bike so physicians can see what’s going on in those narrowed arteries. Medications, such as aspirin and drugs to lower cholesterol, are almost always ordered.

But very often, doctors also refer patients for an invasive procedure to widen the artery. That could mean either inserting a tiny balloon to inflate the artery, followed by placement of a metal tube called a stent to keep the artery propped open, or bypass surgery, when surgeons redirect the flow of blood around the blocked artery.

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"It's common practice, if you have a very abnormal stress test, to go to the cardiac catheterization lab pretty promptly, because [doctors] are afraid that the patient is going to have a heart attack or die," said study leader Dr. Judith Hochman, the senior associate dean for clinical sciences at New York University School of Medicine.

"This study is saying, let's rethink this," she told NBC News.

Hochman and her team of investigators looked at 5,179 patients in 37 countries. All of the patients were put on an intensive drug regimen that included aspirin and medications to lower levels of unhealthy LDL cholesterol, along with blood pressure drugs such as ACE inhibitors and beta blockers.

They were also encouraged to lose weight if necessary, by exercising and cutting down on saturated fat in their diet, and to quit smoking.

Half stuck with this “conservative” approach — medications and lifestyle changes only — as long as their condition didn’t worsen.

The other half got the medications and lifestyle advice, too, but were also referred for either a stent or bypass surgery.

The study found that after four years, the rates of heart attack, cardiovascular death and other bad outcomes were nearly identical in both groups: 13.3 percent in the half that received invasive procedures, versus 15.5 percent in the conservative group.

“It was surprising to find that with modern medical therapy and lifestyle changes, there was no added benefit of an invasive strategy to open those blockages,” Hochman said.

There was one noteworthy difference: Patients who had a surgical intervention reported more chest pain relief than those in the conservative group.

That’s an important consideration for some patients, experts said. Take, for example, an active 60-year-old woman with ischemic heart disease, whose exercise-induced chest pain has forced her to cut back on the tennis she loves. She may opt for immediate relief of her angina with a procedure, in addition to medication.

“We can now sit down with patients armed with the information from this trial and customize a program based upon their wishes,” said Dr. Elliott Antman, a senior physician of cardiovascular medicine at Brigham and Women’s Hospital in Boston. Antman was not involved with the new research, but is a past president of the American Heart Association.

On the other hand, this trial also shows ischemic heart disease patients can do well if they stick to their medications and make aggressive lifestyle changes that push their cholesterol and blood pressure down significantly.

“This is cutting-edge medical therapy that's disease-modifying,” Antman said. “Lowering cholesterol will lead to a less lipid-rich plaque.”

It’s important to note that not all chest pain is equal. If you've never experienced it before, or if it doesn't go away within a few minutes, call 911 immediately.

“Patients who have severe chest pains or who have pain at rest need to clearly understand that this study did not include patients like them,” Levine said.

In those patients, invasive procedures are “often, if not usually, better than just medical therapy alone,” he added.

"If you’re having a heart attack, stents save lives," Hochman said.

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