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Fractional Flow Reserve (FFR) Guides Stent Treatment for So-Called "Widow Maker" Artery
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October 28, 2011 -- A single center registry-based study of 730 patients, published online this week in JACC Interventions, furthers the concept that a treatment strategy for coronary artery disease patients may be guided successfully using Fractional Flow Reserve (FFR). The results of this study show that a significant number of patients with a proximal Left Anterior Descending (LAD) blockage do not need angioplasty or bypass surgery and can be treated safely with medical therapy only.

On CardioSource, the American College of Cardiology's video news site, Peter Block, MD, FACC summed up the message to interventional cardiologists:

"Pay attention to this study! We are going have to become more and more accountable for our decisions in treating coronary artery stenosis with PCI and using FFR may be one way of supporting our decisions."

The patients in this study were selected from 6,107 cases performed at the Cardiovascular Center in Aalst, Belgium from 1998-2008, in which both standard angiography and FFR measurements were done. All patients had an isolated blockage (stenosis) in the proximal Left Anterior Descending (LAD) coronary artery ranging from 30-70%, as judged visually by angiography, and no additional blockages greater than 30% elsewhere.

The usual treatment for a 50% or greater stenosis in the proximal LAD is revascularization with angioplasty, stenting or bypass surgery. However, in this center, if the FFR measurement was 0.80 or higher, the lesion was judged hemodynamically nonsignificant and the patient was not revascularized, but treated medically instead. In fact in this study group, 77% of the patients (n=564) wound up with medical therapy; only 23% of the patients had their blockage opened up, most of them with a stent..

A blockage in the proximal LAD is often nicknamed the "widow maker" because it is the primary coronary artery and, if it were to close down suddenly, would precipitate a catastrophic heart attack (this somewhat sexist nickame is also applied to the Left Main part of the artery which was not part of this study). So conventional wisdom suggests that any significant narrowing in the proximal part of the LAD should be opened up, if possible.

What is a Significant Blockage?
Using angiography, most cardiologists use a visual assessment of a 50% or greater narrowing as the definition of a significant blockage. However, those cardiologists who measure the actual hemodynamics of the blood flow with FFR usually set 0.80 as the dividing line (anything below 0.80 is considered significant because it is limiting blood flow and therefore oxygen delivery).

Interestingly, although this study group included lesions down to 30%, the authors note that almost half of the narrowings that were judged by angiography to be between 50-70% were actually nonsignificant when measured with FFR -- and therefore were not revascularized. Conversely, in the low risk 30-50% group, FFR found "significant" lesions in 10% of the cases -- so angiography alone did not reveal the problem and therefore these patients would not have been treated with angioplasty, a procedure which they actually needed.

Long-Term Results
The entire patient group was followed for a median of 40 months and the 5-year survival rate was compared to a reference population free of coronary artery disease. The result: the 5-year survival estimate was 92.9% in the medical group versus 87.4% in the group that was revascularized versus 89.6% in the reference group (with no disease) -- there was no statistically significant difference among these groups. So not performing a procedure (angioplasty or bypass) in the group with an FFR of 0.80 or above was the correct choice. These results reinforce those seen in previous large randomized trials, such as DEFER and FAME. In fact, the FAME study showed that stenting a hemodynamically insignificant lesion may actually lead to worse outcomes.

Limitations of the Study and Clinical Significance
The authors note that this patient population was mostly stable patients and that, of the medically-treated group, only 23% had a blockage that was 50% or larger. Also this was a single-center registry study with a relatively homogenous patient population in Belgium. However, the very important conclusion is that it is safe to defer revascularization in these types of lesions when FFR shows no hemodynamic significance, and to treat with medical therapy only, even though angiography shows a "significant" blockage. Secondarily, it is also important to determine hemodynamic significance in "low risk" lesions, because what looks like low risk on angiography may in fact be significant when measured with FFR. Finally, the authors note that almost 50% of patients arriving in the cath lab have not, for one reason or another, ever been given a prior functional measurement for ischemia, such as a nuclear stress test. Utilizing fractional flow reserve, an accurate and fast functional measurement can be made at the same time as the angiogram, so that the proper treatment can be determined.

This study, "Long-Term Follow-Up After Fractional Flow Reserve–Guided Treatment Strategy in Patients With an Isolated Proximal Left Anterior Descending Coronary Artery Stenosis", by Olivier Muller, MD, PHD et al, is yet another data point in the growing array of evidence regarding fractional flow reserve. As the authors write:

"It is now widely recognized that the angiogram is a poor tool to gauge the functional significance of a coronary stenosis. When revascularization is based mainly on angiographic guidance, it is unavoidable that a number of hemodynamically nonsignificant stenoses will be revascularized, whereas a number of stenoses deemed nonsignificant will be deferred inappropriately. Fractional flow reserve (FFR) is a well-validated method to quantify the impact of a coronary stenosis on myocardial perfusion. FFR...can be obtained in a few minutes in the catheterization laboratory, allowing an "on the spot" decision about the appropriateness of revascularization."


Reported by Burt Cohen, October 28, 2011