Doctors could improve patient outcomes if they did more in-depth measurements of blood flow in the vessels to the heart with fractional flow reserve (FFR) to determine if stenting was the best option, according to the FAME study published Jan. 15 in the New England Journal of Medicine.
“Not only were the outcomes better, the cost was less,” said William Fearon, MD, co-principal investigator of the study and assistant professor of cardiovascular medicine at the Stanford University School of Medicine in Stanford, Calif. “Now there's scientific support for cardiologists to apply this new technique.”
The study suggests that doctors should go one step beyond the traditional method of relying solely on x-rays from a coronary angiogram to determine which arteries should be stented for patients with coronary artery disease. In many cases, cardiologists will routinely stent any arteries that look significantly narrowed on the angiogram, according to Fearon. “The problem is you can't always tell from the angiogram whether this is absolutely necessary,” he said.
By using FFR, which involves inserting a coronary pressure guidewire into the artery, doctors can measure whether blood flow is actually reduced to a dangerous level beyond any apparent narrowing.
The study included about 1,000 patients in the U.S. and Europe at 20 hospitals—six from the U.S. Patients included in the study either suffered from chest pains or were recovering from mild MIs. All patients had multiple coronary arteries with narrowings.
About half the patients were treated with the traditional method of using an angiogram to decide which narrowings to stent. The other half of the patients underwent the angiogram with the additional pressure-wire technique. To measure blood flow beyond the areas in the arteries that appear narrowed, the pressure wire was threaded through the same catheter used for the angiogram.
“If the pressure was 80 percent or less than the pressure in front of the narrowing (an FFR value of .80 or less), a stent was implanted,” Fearon explained.
Researchers found that patients who received the additional blood flow test received one-third fewer stents than the group examined only with an angiogram. Those patients received 2.7 stents on average. The other half, who had their blood flow measured in each artery, received 1.9 stents on average.
After one year, data showed that within the traditional group, 18.4 percent of the patients had died, suffered an MI or needed a bypass surgery or repeat stent procedure, compared with 13.2 percent among those who received the additional pressure wire test.
“We are most excited about the 30 to 40 percent decrease in cardiac events, including death, heart attack and the need for repeat stenting or bypass surgery,” Fearon said. “The improvement was so striking it can hardly be ignored.”
The new procedure did not require any extra procedural time and resulted in decreased medical costs, the authors wrote. “Each stent on average costs roughly $2,000,” Fearon said. "The pressure wire test runs an additional $700.” Using fewer stents also results in using a decreased amount of contrast dye.
“The take-home message is that the wire is able to give you more information about whether a coronary narrowing is truly causing abnormal blood flow to the heart," Fearon said. “Some narrowings that might look bad would respond just as well to medication, while others that appear innocent may benefit from stenting. By measuring FFR, one is better able to make this distinction and improve the patient's outcome, while also saving healthcare dollars.”
The study was funded by Radi Medical Systems in Uppsala, Sweden, which was recently acquired by St. Paul, Minn.-based St. Jude Medical.