Healthcare Industry News: fractional flow reserve
News Release - May 21, 2007
Five-Year Fractional Flow Reserve Data Confirms Benefit of Deferral of StentingRadi PressureWire(R) System Provides Definitive Information About Which Lesions To Stent And Those Which May Be Deferred
WILMINGTON, Mass., May 21 (HSMN NewsFeed) -- Patients treated based on fractional flow reserve (FFR) results achieve long term outcomes equal, or superior to, patients who undergo stenting solely based on angiographic evidence according to the results of a study being published in the May 29 issue of the Journal of the American College of Cardiology. The authors report the five-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.
Dr. 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."
Current guidelines state that evidence must exist demonstrating that a stenosis is actually causing reduced blood flow (ischemia) before it would be considered for percutaneous coronary intervention (PCI). This study concludes that stenting any lesion with an FFR of 0.75 or more (blood flow through the narrowed area of the artery that is at least 75 percent of normal) does not relieve any symptoms or prevent future cardiac events.
"Given the absence of patient benefit, the potential risks of heart attack or restenosis associated with the PCI procedure itself, and the high cost of PCI, using FFR technology to determine with certainty which lesions are significant and which can safely be left alone would seem to be warranted in every cath lab," said Morton Kern, MD, Associate Chief, Division of Cardiology, University of California, Irvine. "The study results show the practice of stenting an intermediate lesion merely because it visually appears to be significant is of questionable value."
This prospective, randomized study involved 325 patients with stable chest pain scheduled for elective PCI of a single stenosis deemed significant based on visual assessment of an angiogram. Prior to any physiologic testing being performed, 167 patients were randomly selected to have PCI deferred (DEFER group); the remaining 158 were assigned to have PCI performed (the PERFORM group).
FFR was then obtained on all patients using the Radi PressureWireŽ. All patients who had an FFR less than 0.75 in the suspected vessel were treated with a bare metal stent (the REFERENCE group), regardless of their initial randomization.
A total of 144 patients received stents (FFR < 0.75); 91 patients with FFRs of 0.75 or more were deferred from PCI and 90 patients with FFRs of 0.75 or more underwent PCI. Study patient medications were continued through the study at pre-study levels.
The primary study outcome was freedom from adverse cardiac events after two years of follow-up. Adverse cardiac events were defined as all-cause mortality, heart attack (MI), coronary artery bypass grafting surgery, and coronary angioplasty. Freedom from cardiac events after 5 years was a secondary end point, as was freedom from chest pain at all follow-up periods and the use of drugs to manage chest pain (antianginal drugs).
Study Results Confirm FFR as Key Measurement in Treatment Decisions
The results show that the risk of a stenosis causing death or AMI is less than one percent per year when FFR is > 0.75 and stenting is deferred. Stenting these patients does not improve outcomes.
After five-years of follow-up, there were no statistical differences between the DEFER (FFR>0.75, no stent) and PERFORM (FFR>0.75 with stent) groups in terms of event-free survival (79% vs. 73%) and freedom from chest pain (67% vs. 57%). Importantly the composite rates of cardiac death and acute myocardial infarction yielded 3.3% vs. 7.9%. In addition, the use of medicines to manage chest pain and high blood lipids was identical (92% vs. 92%) in the two groups.
Conversely, cardiac events after 5 years were significantly (p=0.03) higher in the REFERENCE (FFR<0.75 with stent) group than in either the DEFER or PERFORM groups. This confirms the conclusions of earlier studies that lesions with an FFR less than 0.75 are functionally significant and should be treated because these are the lesions that cause cardiac events.
"The use of a simple and quick diagnostic tool like the Radi PressureWireŽ enables an interventional cardiologist to determine with specificity whether a particular lesion is actually limiting blood flow. This advantage cannot be overstated," said Dr. Kern. "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 what this study proves are non-beneficial procedures."
"The key issue is the presence of ischemia and the most accurate, quickest, and most practical way to judge ischemia is measuring coronary pressure and FFR," Dr. Pijls concluded.
FFR expresses maximum achievable blood flow in a coronary artery with abnormal stenosis as a fraction of normal maximum blood flow in the absence of a stenosis. It is calculated using an interventional guidewire with a specially designed sensor built into it. Using the well established value of 0.75, FFR is 100% specific in identifying which lesions are actually causing flow restriction and can be treated. FFR also documents the exact percentage of the reduction in flow associated with each lesion.
About Radi PressureWireŽ
The PressureWireŽ system from Radi Medical Systems consists of the sensing guidewire and a proprietary monitor which calculate fractional flow reserve (FFR) in coronary arteries. Assessment of FFR with the newest version, PressureWireŽ Certus, provides physicians with valuable information on which to form clinical decisions on coronary vascular evaluation.
About Radi Medical Systems AB
Radi Medical Systems AB develops, manufactures and sells medical devices designed to improve patient care. Its pioneering work within the field of interventional cardiology has resulted in market-leading intravascular sensors and hemostasis management and radiology devices. Radi continues to work closely with medical practitioners to develop solutions that address clinical needs, as well as providing clinical education support. Founded in 1988, Radi Medical Systems employs more than 350 people globally with representation in more than 40 countries. Radi Medical Systems is based in Uppsala, Sweden; its United States headquarters are in Wilmington, Massachusetts.
Source: Radi Medical Systems
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