Fractional Flow Reserve Measurement
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Fractional flow reserve (FFR) measurement involves determining the ratio between the maximum achievable blood flow in a diseased coronary artery and the theoretical maximum flow in a normal coronary artery. An FFR of 1.0 is widely accepted as normal. An FFR lower than 0.75-0.80 is generally considered to be associated with myocardial ischemia (MI). [1]
FFR is easily measured during routine coronary angiography by using a pressure wire to calculate the ratio between coronary pressure distal to a coronary artery stenosis and aortic pressure under conditions of maximum myocardial hyperemia. [1] This ratio represents the potential decrease in coronary flow distal to the coronary stenosis.
Over the past decade, FFR measurement has been increasingly used in cardiac catheterization laboratories. It provides a quantitative assessment of the functional severity of a coronary artery stenosis identified during coronary angiography and cardiac catheterization.
A severe coronary artery stenosis can limit myocardial blood flow, resulting in MI. In most cases, the severity of a coronary artery stenosis is judged by visual inspection by the cardiologist during cardiac angiography. A lesion is generally considered severe and flow-limiting if the narrowing of the luminal diameter is estimated to be 70% or greater. [2]
During angiography, the cardiologist typically assesses the patient’s symptoms and clinical characteristics, evaluates the angiographic appearance of the coronary tree, and then decides whether revascularization with angioplasty, stenting, or coronary bypass surgery is most appropriate. [2]
However, the ability of the cardiologist to discriminate between lesions that can cause MI and lesions that are physiologically insignificant on the basis of coronary angiography alone is limited. [3] The use of FFR measurement provides the cardiologist with a straightforward, readily available, quantitative technique for evaluating the physiologic significance of a coronary stenosis.
Indications for FFR measurement are as follows:
To determine the physiologic and hemodynamic significance of an angiographically intermediate coronary stenosis
To identify appropriate culprit lesion(s) in multivessel coronary artery disease (CAD)
To measure the functional importance of stenosis in the presence of distal collateral flow
To identify the precise location of a coronary lesion when the angiographic image is unclear
Note that this procedure is not intended for use in the setting of a total vessel occlusion.
In a study designed to test the hypothesis that experienced interventional cardiologists could identify patients with FFRs below 0.75 by means of coronary angiography, FFR was measured in 83 angiographically moderate coronary lesions, which were also visually assessed by 3 interventional cardiologists; the reviewers’ classification matched the FFR in only about half of the lesions, and concordance between reviewers was poor. [4]
In this study, when visual assessment was compared with FFR, it resulted in good sensitivity (80%) and negative predictive value (91%) but poor specificity (47%) and positive predictive value (25%). [4] Angiographic assessment of an angiogram by experienced interventional cardiologists did not predict the significance of most moderate coronary lesions.
In the DEFER study, which assessed patients with single-vessel CAD and angiographically intermediate coronary stenosis, patients with an FFR above 0.75 were randomized to either medical management or stent implantation; at 5-year follow-up, those who did not receive a stent had the same risk of death or acute MI as those who did, which suggests that patients with an FFR higher than 0.75 do not benefit from revascularization of the stenosis. [5]
The Fractional Flow Reserve versus Angiography for Multivessel Evaluation (FAME) study, which studied the role of FFR in the evaluation of multivessel CAD, reported results suggesting that a revascularization strategy using FFR yields superior clinical outcomes in patients with multivessel CAD. [6]
In this study, patients with multivessel CAD identified by angiography were randomized to undergo either angiography alone or FFR plus angiography. [6] Patients in the angiography-only arm underwent stenting of all angiographically severe lesions. Patients in the FFR-plus-angiography arm underwent stenting only if FFR was 0.80 or less. At 2-year follow-up, patients who underwent FFR-driven stenting had fewer stents than those in the angiography-only group, along with reductions in mortality, MI, and repeat revascularization.
Pijls NH, De Bruyne B, Peels K, et al. Measurement of fractional flow reserve to assess the functional severity of coronary-artery stenoses. N Engl J Med. 1996 Jun 27. 334(26):1703-8. [Medline].
Silber S, Albertsson P, Aviles FF, et al. Guidelines for percutaneous coronary interventions. The Task Force for Percutaneous Coronary Interventions of the European Society of Cardiology. Eur Heart J. 2005 Apr. 26(8):804-47. [Medline].
Bartunek J, Sys SU, Heyndrickx GR, Pijls NH, De Bruyne B. Quantitative coronary angiography in predicting functional significance of stenoses in an unselected patient cohort. J Am Coll Cardiol. 1995 Aug. 26(2):328-34. [Medline].
Fischer JJ, Samady H, McPherson JA, et al. Comparison between visual assessment and quantitative angiography versus fractional flow reserve for native coronary narrowings of moderate severity. Am J Cardiol. 2002 Aug 1. 90(3):210-5. [Medline].
Pijls NH, van Schaardenburgh P, Manoharan G, et al. Percutaneous coronary intervention of functionally nonsignificant stenosis: 5-year follow-up of the DEFER Study. J Am Coll Cardiol. 2007 May 29. 49(21):2105-11. [Medline].
Tonino PA, De Bruyne B, Pijls NH, et al. Fractional flow reserve versus angiography for guiding percutaneous coronary intervention. N Engl J Med. 2009 Jan 15. 360(3):213-24. [Medline].
Coronary physiology: overview. Volcano Corporation. Available at http://www.volcanocorp.com/products/functional-measurement.asp. Accessed: 5/28/2010.
St Jude Medical. Available at http://www.radi.se/kc_home.aspx?n=start&r=1. Accessed: 5/28/2010.
Diletti R, Van Mieghem NM, Valgimigli M, et al. Rapid exchange ultra-thin microcatheter using fibre-optic sensing technology for measurement of intracoronary fractional flow reserve. EuroIntervention. 2015 Aug. 11(4):428-32. [Medline].
Verdier-Watts F, Rioufol G, Mewton N, et al. Influence of arterial hypotension on fractional flow reserve measurements. EuroIntervention. 2015 Aug. 11(4):416-20. [Medline].
Eiman Jahangir, MD, FACC Cardiologist
Eiman Jahangir, MD, FACC is a member of the following medical societies: American College of Cardiology, American Heart Association
Disclosure: Nothing to disclose.
John A McPherson, MD, FACC, FACP Professor of Medicine, Sol and Marvin Rosenblum Chair in Medical Education, Vice-Chair for Education, Department of Medicine, Vanderbilt University Medical Center
John A McPherson, MD, FACC, FACP is a member of the following medical societies: Alpha Omega Alpha, American College of Cardiology, American College of Physicians, American Heart Association, Association of Program Directors in Internal Medicine
Disclosure: Nothing to disclose.
Karlheinz Peter, MD, PhD Professor of Medicine, Monash University; Head of Centre of Thrombosis and Myocardial Infarction, Head of Division of Atherothrombosis and Vascular Biology, Associate Director, Baker Heart Research Institute; Interventional Cardiologist, The Alfred Hospital, Australia
Karlheinz Peter, MD, PhD is a member of the following medical societies: American Heart Association, German Cardiac Society, Cardiac Society of Australia and New Zealand
Disclosure: Nothing to disclose.
Fractional Flow Reserve Measurement
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