FFR and Choosing an Optimal Revascularization Strategy

It provides a very easy-to-interpret value that helps physicians determine the significance of a coronary lesion seen on angiography. Its most important role is to help us to understand whether or not a lesion is capable of resulting in ischemia. This information is particularly important when the angiogram is unclear or if the lesion appears to narrow the lumen to only a moderate degree. Importantly, FFR is a value that is precise and not subject to interpretation. It provides us with physiologic and not just anatomical information. Why is physiological information about the lesion important? Primarily because the anatomical information provided by angiography has important limitations. Angiography is helpful when an artery is normal or when there is an unequivocally severe lesion. Very often, however, angiography reveals lesions that are only moderate, or appear hazy and eccentric or are just not well seen because of vessel tortuosity or overlap. Under these circumstances, most angiographers have to guess as to whether or not the lesion is severe enough to cause ischemia and they are very often wrong. FFR gets away from the whole anatomical concept and, instead, tells you the impact of a lesion on coronary blood flow to the myocardium supplied by the artery in question. This is much more important, since a physiologic-based measurement allows the physician greater confidence in choosing an optimal revascularization strategy (surgery versus intervention) and more importantly, it helps to determine if the patient is likely to benefit from a revascularization procedure. Anatomy alone is often unable to give us that information. How did the DEFER study affect your thinking and use of FFR? The DEFER study provided me with great confidence that decisions I make based on fractional flow reserve assessment will translate to patient benefit. Importantly, I can very confidently leave alone a lesion that we find to be non-flow limiting by FFR, without worry about the patient’s risk for either acute myocardial infarction or death. I can reassure the patient that if the FFR is not ischemic, medical therapy is their best treatment option and revascularization is unnecessary. Could you share a recent case that details the use of a pressure guidewire in your practice? We use the PressureWire very commonly and find it indispensable in the practice of interventional cardiology. Probably the most common instance where we use the PressureWire is as an adjunct to angiography, when a lesion appears to be of unclear significance. When you find yourself staring at angiogram, taking multiple views, and replaying the angiogram over and over, it means you are really unsure of the lesion significance. That’s the time to measure FFR. Our most common indication is for assessment of indeterminate lesions, something in the 50 to 70 percent range. This is particularly true if the patient has multi-vessel disease, with several potentially significant lesions and you are trying to decide between bypass surgery and intervention. The other big category is patients who have intermediate lesions and somewhat atypical symptoms, making it difficult to determine if the disease you are seeing is responsible for their symptoms. This is where FFR can really help us since they are unlikely to benefit from a stent if the lesion you are seeing is not significant. Some other important areas where we measure FFR in practice are to assess left main lesions, ostial lesions, or lesions of side branches, which are often very difficult or at increased risk to treat and are notoriously difficult to properly assess by angiography. In the case of ostial or side-branch stenoses, although they often appear narrowed by angiography, they often are not significant by FFR and can be safely left alone. One recent example is a case of a 63-year-old gentleman presenting with increasing angina, despite medical therapy. He undergoes a stress test, which shows a fairly clear-cut defect with evidence of ischemia in the inferior wall only. The patient is referred for catheterization and we find him to have very severe disease in the right coronary artery, as we would predict based on the stress test. But he also has disease in the left anterior descending artery that, by the angiogram, appears moderate, no more than probably 50 to 60 percent narrowed. Despite multiple views, it doesn’t look that severe. The right coronary is implicated by the stress test but the patient has another suspect lesion. We treated this patient’s right coronary artery with a stent and then measured FFR in the left anterior descending artery and, to our surprise, we found that to be a significant lesion with an FFR of 0.65 and therefore likely to cause ischemia and on-going angina if it had been left alone. The left anterior descending artery was also treated. I think this case is not only very important, but a very common scenario because first, it demonstrates a weakness of stress testing since stress imaging primarily identifies only the worse stenosis. Therefore, you can not use a stress test to help decide whether other lesions seen on an angiogram are significant or not; it only finds and identifies the most severe stenosis. The second point this case demonstrates is that angiography is limited and we can only go so far with interpretation, particularly in these moderate lesions. We are sometimes wrong about them when we make a decision based on the angiogram alone. FFR leaves no doubt in the mind of the operator. The more it is used, the more you learn that you just can not rely on the angiogram alone. Those of us who use it routinely feel like you can not live without it. It is really a very important part of doing catheterization and intervention. What is the primary challenge behind the use of a pressure guidewire? I don’t know why pressure guidewires are not used more widely. Our laboratory finds the PressureWire very easy to use and very easy to interpret, so I don’t think there is a technical issue there. It usually takes the nurses and technologists just a few minutes to set up and just a few minutes for the physician to perform and obtain numbers. The outcomes data have been available for some time now, so the benefits should be well-known and operators can be confident in their decisions based on FFR. And again, for most physicians, once they start to use it, they gain their own experience where they are surprised and realize they cannot predict lesion significance by angiography alone. Once you have had a few experiences where you were ready to dismiss a lesion as insignificant, then learn that the FFR is at an ischemic value, you realize that you really cannot practice without a pressure guidewire. It takes all doubt away and makes you very confident in your decisions. Dr. Michael Ragosta can be contacted at mr8b@virginia.edu

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