FPD and FFR: Tools for Better Decision-making

Flat-panel detectors (FPD) offer improved resolution over image intensifiers, reducing motion blurring and making then ideal for high-speed imaging such as angiography of a beating heart. Along with flat-panel detectors, fractional flow reserve (FFR) is helping physicians obtain more accurate information about suspect lesions in the coronary artery. Some interventional cardiologists say the combination of technology leads them to better decision-making when it comes to diagnosis and treatment.

Radi PressureWire is used to calculate FFR in the cath lab, providing interventional cardiologists with more accurate data for decision-making.

In a cath lab or radiology suite, physicians have the ability to perform a stress test and an angiogram. But some experts say angiography has its limitations. While an angiogram is essentially a vessel picture, fractional flow reserve is a measurement—it provides objective, concrete data about a lesion. “Essentially, FFR provides a measure that guides your decision to treat or not to treat,” said interventional cardiologist Morton Kern, MD, associate chief and director of clinical affairs, division of cardiology, University of California, Irvine. “If the pressure measure is within the normal range and you don’t need to stent it, then don’t.”

Perhaps more importantly, Kern points out that FFR in conjunction with flat-panel detectors can mean the difference between “going for bypass surgery or not going.” It’s a tool Kern says is not used often enough, probably because it takes time to train physicians and perhaps because of reimbursement issues. Still, Kern believes physicians’ traditional “visual teaching” is not enough. “It’s not enough to look at a lesion and make diagnosis and treatment decisions,” Kern said. “Just because we see it, doesn’t mean we need to treat it mechanically if the flow is normal.” With FFR, cardiologists have an objective, scientific measurement to guide next-step decisions.

Kern uses the Radi PressureWire, which is essentially a guidewire with a sensor on the tip that calculates FFR in coronary arteries. Flat-panel detectors are used in conjunction during the procedure to guide physicians. Experts say the benefits for FPD image quality include lack of geometric distortion, little or no veiling glare, and a uniform response across the field of view.

“The use of a simple and quick diagnostic tool like the Radi PressureWire enables an interventional cardiologist to determine with specificity whether a particular lesion is actually limiting blood flow. This advantage cannot be overstated,” Kern said. “Angiogram results often suggest but do not clearly display a significant stenosis. Measuring FFR can help define the clinical importance of the stenosis and eliminate nonbeneficial procedures.”

In fact, a study published in the Journal of the American College of Cardiology (May 29, 2007) showed that patients treated based on fractional flow reserve results achieve long-term outcomes equal, or superior, to patients who undergo stenting solely based on angiographic evidence. The authors reported the 5-year follow-up results of the DEFER study, which investigated the appropriateness of stenting a coronary stenosis (abnormal narrowing) that appears to be angiographically significant but is not restricting blood flow enough to cause symptoms.

The study showed that FFR can be an effective way to assess lesion severity. By measuring pressure gradient across a questionable blockage, FFR provides a key objective benchmark from which to guide appropriate therapy. If the FFR is below 0.75, data suggest that the lesion will likely be associated with ischemia. In these cases, PCI should alleviate symptoms. If the FFR is above 0.75, data suggest the patient may benefit from medical therapy, follow-up, and no stenting.

Nico Pijls, the study’s principal investigator, said, “From the DEFER study and other recent publications, it has become clear that the key issue in deciding which lesions should be stented is knowledge about whether a stenosis is responsible for ischemia.”

Dimitri Sherev, MD, cardiovascular medicine and interventional cardiology at Sharp Memorial and Sharp Grossmont Hospitals in San Diego, uses FFR on a daily basis in the cath lab. “FFR guides us to make the right decisions for each patient,” Sherev said. “It’s a tool that can help ensure a patient survives longer and has a better quality of life.”

Like Kern, Sherev cautions against relying on the human eye. “You can’t just rely on the visual interpretation of an angiogram,” Sherev said. “It’s critical to know the exact pressure and then correlate that with studies and outcomes. Then you feel confident with your decisions.”

Sherev credits today’s flat-panel detectors with aiding FFR. “Every standard cath lab relies on flat panel detectors today,” Sherev said. “They are far better than the image intensifiers we used previously.”

For interventional cardiologists there is little financial incentive to use FFR. Often, a diagnostic cardiologist does the angiogram and the FFR is a Medicare “add-on” code. If the interventional cardiologist does not do the angiogram, he or she will not be reimbursed.

For Sherev, however, there are other incentives to continue using FFR. “You benefit because you become known as a professional who does the right thing.” That says Sherev can lead to referrals. But more importantly, he said, “There is the personal satisfaction that I’ve done the appropriate and best thing for my patients. I’ve guided my decisions by using scientific measures.”

—Marianne Matthews