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Posts Tagged ‘Fractional Flow Reserve (FFR)’


Reporter: Aviva Lev-Ari, PhD, RN

Updated 3/10/2013

Since August 25, 2012, when the ESC: New Definition of MI Unveiled was reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco as was reported  By Chris Kaiser, Cardiology Editor, MedPage Today,  a new discussion emerged by ACC asking if FFR CT is Ready for prime time or not?

By Lisa Fratt
Mar 09, 2013

SAN FRANCISCO—Is there a better way to measure fractional flow reserve (FFR), Bon-Kwon Koo, MD, of Seoul National University queried a crowded room March 9 during an educational session at the American College of Cardiology (ACC) scientific session.

The current model is good for patients, safe and effective, Koo said. However, it requires an invasive procedure and is expensive. FFR CT may provide a method to measure FFR without an invasive procedure.

FFRCT extracts geometry from a CT scan to determine boundary conditions and fluid properties. In addition, velocity and pressure can be calculated. The hitch is that a supercomputer is required to solve the blood flow equation, said Koo. The results provide anatomical and functional data, thus giving a possible answer to the question at hand.

FFRCT may change daily practice in several ways. Most importantly, it may be a novel, fast, risk-free, noninvasive cost-saving way to measure FFR and identify patients who may not need to be sent to the cath lab for stenting or PCI. It can provide information to help surgeons plan strategies before invasive procedures, bypass procedures or interventional procedures. Noninvasive CT-derived FFR also can predict the functional significance of coronary lesions.

Despite its promise, however, FFR CT is not ready for prime time, Koo said. FFR CT depends on the diagnostic accuracy of coronary CT angiography stenosis, which is less than true stenosis. With current technologies, true stenosis provides the required diagnostic accuracy.

FFRCT is promising, but further development of the technology is required, Koo concluded.

http://www.cardiovascularbusiness.com/topics/imaging/acc-ffrct—ready-prime-time-or-not

ESC: New Definition of MI Unveiled

By Chris Kaiser, Cardiology Editor, MedPage Today

Published: August 25, 2012

Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco

MUNICH — An international, multispecialty task force has published a new definition of myocardial infarction that was prompted by the new generation of highly sensitive cardiac troponin (cTn) assays.

The highly sensitive assays are capable of detecting cTn in conditions other than MI, such as pulmonary embolism, cardiomyopathy, and left bundle branch block, and so result in false positives, according to the task force writing group.

The expert consensus document dips into a controversial area by setting levels of cTn for MI associated with percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG).

“This is one of the most controversial areas in the definition of myocardial infarction,” Anthony DeMaria, MD, from the University of California in San Diego and editor-in-chief of the Journal of the American College of Cardiology, told MedPage Today.

“There are a large number of people undergoing PCI in the setting of an acute MI. It’s almost impossible to know whether a subsequent increase in troponin was part and parcel of the acute MI or related to the procedure itself,” DeMaria said.

The consensus document, titled “Third Universal Definition of Myocardial Infarction,” set the cTn levels for MI associated with PCI as elevation of troponin greater than 5 times the 99th percentile upper reference limit (URL) in patients with normal baseline levels or a rise in troponin values greater than 20% if the baseline values are elevated and are stable or falling.

“Some people speculate that troponin may be too sensitive in this situation and what is needed is evidence that an elevation of some degree of troponin following a procedure actually results in some alteration of the natural history of the patient,” DeMaria said. “In other words, the definition of acute MI after a procedure really is of significance if it increases the risk of subsequent events such as death.”

In CABG, the task force set the troponin values as greater than 10 x 99th percentile URL during the first 48 hours when baseline values are normal.

DeMaria said there are several ongoing studies examining the correlation of elevated cTn with subsequent events. As this is the third definition of MI since 2000, there most likely will be more refinements as new data emerge, he said.

The document is being copublished online in several journals including the Journal of the American College of CardiologyCirculation, the European Heart Journal, and Global Heart.

The task force was in touch with the FDA during the development of this new definition, which means it could be used as the basis for clinical trial protocols designed according to FDA regulations.

“A universal definition for MI is of great benefit for clinical studies, since it will allow a standardized approach for interpretation and comparison across different trials,” the task force writing group explained.

When different definitions have been used in trials, it hampers “comparison and generalization between these trials,” they said.

Also of significance in this document is the inclusion of imaging as a means to identify or confirm an MI. The document spells out the strengths of echocardiography, nuclear imaging, MRI, and CT in the setting of acute MI.

“Imaging is playing an increasingly important role,” DeMaria said. “In the absence of focal symptoms or with an inconclusive ECG, it’s important to recognize the concomitant potential of ancillary measures, primarily imaging, to help with the diagnosis of a myocardial infarction.”

Thygesen reported relationships with Edwards Lifesciences, Servier, St. Jude Medical, Roche Pharma, and Roche Diagnostics. Her co-authors and reviewers reported relationships with Bayer Healthcare, Daiichi Sankyo, Johnson & Johnson, sanofi aventis, Servier, Novartis, Boehringer-Ingelheim, Genzyme, Eli Lilly, OrthoClinical Diagnostics, Abbott Laboratories, Alere, Brahms, Siemens Healthcare, Roche Pharma, Radiometer, BioRad, Diagenics, Response Medical, Takeda Pharmaceuticals, Regado Biosciences, Bristol-Myers Squibb, Merck Sharp and Dohme, GlaxoSmithKline, Merck, Portola Pharmaceuticals, AstraZeneca, Regado Biosciences, Scios, Ortho-Biotech, Pfizer, Kai Pharmaceuticals, Iroko Cardio, Philips, GE Healthcare, Boston Scientific, Lantheus, Medtronic, St. Jude Medical, Biotronik, Impulse Dynamics, Edwards Lifesciences, Health System Networks, Health Station Networks, Insight Telehealth Systems, Elsevier Sciences, Gilead, Evolva, Medicines Company, F. Hoffman La Roche, Torrent, Vifor International, Corthera, Nanosphere, Bayer Schering Pharma, Cardiorentis, Molecular Insight Pharmaceuticals, Berlin Chemie, Menarini, Cordis, Beckman Coulter, Amgen, Critical Diagnostics, Tethys Bioscience, Roche Diagnostics, bioMérieux, Genentech, Ikaria, Singulex, BG Medicine, Shionogi, Amylin, DiaDexus, Orion, WebMD, theheart.org, Pozen, Maquet, BHFZ, Covidien, Rapidscan, Actelion, Athera, Symetis, Schering-Plough, OrbusNeich, Terumo, Cardio3 Biosciences, Micell, Ablynx, Therabel, Kowa, Zentiva, Chugai Pharma, Automedics Medical Systems, Essentialis, Biosensors, Vascular Solutions, Zoll Medical, JaBA Recordati, Actavis, PharmaSwiss, Eisai, Medscape, Accumetrics, Bial Portela, AGA, Novo-Nordisk, Janssen-Cilag, Valtech, Otsuka Pharmaceuticals, Meda Pharma, CEPHALON, Intracellular Therapies USA, Santhera, TROPHOS, Pierre-Fabre, and Lundbeck.

DeMaria reported relationships with Gilead, ResMed Foundation, Lantheus, Cardiovascular Biotherapeutics, Angioblast Systems, General Electric Medical Systems, and Cardionet.

Primary source: European Heart Journal

Source reference:
Thygesen K, et al “Third universal definition of myocardial infarction” Eur Heart J 2012; DOI: 10.1093/eurheartj/ehs184.

ESC: FFR CT Has Potential for Tagging Ischemia

By Chris Kaiser, Cardiology Editor, MedPage Today

Published: August 26, 2012

Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco

MUNICH — Using CT imaging to assess the hemodynamic significance of coronary lesions is “promising” but needs more research before it displaces conventional invasive fractional flow reserve (FFR), researchers said.

Using FFR as the reference standard, FFRCTplus CT angiography (CTA) had good sensitivity (90%) and negative predictive value (84%) on a per patient basis for detecting ischemia, which indicates a low rate of false-negative studies, according to James K. Min, MD, of Cedars-Sinai Heart Institute in Los Angeles, and colleagues.

Although FFRCT plus CTA were superior to CTA alone, the specificity (54%) and negative predictive value (67%) of the combination remained low compared with conventional FFR, indicating that a considerable number of false-positive studies would endure, Min reported here during a Hot-Line session at the European Society of Cardiology meeting.

The results of this proof of concept study show that FFRCT can “impart considerable discriminatory power” to detect and exclude ischemia in patients with suspected CAD, Min said.

However, future studies should be conducted to determine the cost-effectiveness of FFRCT in guiding decisions to stent, particularly given the potentially high false-positive rate, he added.

“Non-invasive FFR is a dream for all interventional cardiologists,” said study discussant Jean-Pierre Bassand, MD, of the University Hospital Jean-Minjoz in Besançon, France. Although Bassand praised the DeFACTO study, he expressed concern about the discrepancy between the accuracy of FFR versus FFRCT.

For example, compared with FFR, the sensitivity and specificity of FFRCT in cases of greater than 90% or less than 30% stenosis were 83% and 76%, respectively. The per-vessel correlation of FFRCT to FFR was 0.63.

“What matters is the correlation with FFR,” he concluded.

A single non-invasive imaging test that can identify obstructive coronary artery disease (CAD) and determine the physiological significance of those lesions would be ideal. At present, nuclear stress imaging fulfills the first part, but it cannot label stenoses as hemodynamically significant or not. Also, nuclear stress testing suffers from high rates of both false-negative and false-positive studies, Min said.

The results of this study are in line with stress imaging: per patient diagnostic accuracy of 73% (95% CI 67% to 78%). Min said that studies are being designed to compare FFRCT plus CTA with stress imaging.

“For patients considered for invasive therapy, this type of test could help exclude those who don’t need to be stented,” Spencer King III, MD, of St. Joseph’s Hospital in Atlanta told MedPage Today.

“The excitement about this CT approach is that it moves things closer to being able to assess physiology and anatomy in a single non-invasive test,” added King, who is also a past president of the American College of Cardiology.

However, the process of calculating the FFR values from CT data currently takes about 6 hours, Min told MedPage Today. The CT data are sent offsite to HeartFlow, the company that makes the software. Whether such processing would be done onsite in the future is not yet determined, Min said. He also expects the processing time to drop to about 2 hours by the year’s end.

HeartFlow has already received EU mark to use the software in Europe and is in the process of applying for FDA approval, Min said.

Conventional FFR uses a pressure wire inserted through the groin to the coronary arteries to determine the hemodynamic significance of lesions. The same data can be gleaned during a typical CTA exam with software that calculates computational fluid dynamics,without additional radiation exposure. The median radiation exposure among the study centers was 6.4 mSv (range 4.4 to 15 mSv).

The original FAME study found the use of FFR to guide stenting was better than relying on angiography alone in patients with multivessel disease. A second study, FAME II, was stopped early because of the overwhelming benefit seen in patients with stable CAD when FFR guided stenting versus patients randomized to optimal medical therapy.

Because FFRCT is a novel technique, it has not been adequately evaluated in its ability to identify patients with ischemia, Min said.

The researchers therefore designed the DeFACTO (Determination of Fractional Flow Reserve by Anatomic Computed Tomographic Angiography) study, which sought to evaluate the accuracy of FFRCT while using invasive FFR as the reference standard.

The study was also simultaneously published online in the Journal of the American Medical Association.

The 252 patients with suspected or known CAD were recruited from 17 centers in five countries between October 2010 and October 2011. They were scheduled to undergo diagnostic catheter angiography.

The mean age of patients was 63, 70% were men, and a majority were white. Nearly half of the patients had obstructive CAD (>50% stenosis).

Among 615 study vessels, 271 had less than 30% stenosis and 101 had at least 90% stenosis. Invasive coronary angiography and FFR identified 46.5% of 408 vessels with obstructive CAD, while CT and FFRCT identified 52.3% of 406 vessels.

A total of 172 patients had an FFR value <0.80, which indicates an ischemic lesion.

The diagnostic accuracy of FFRCT plus CT was 73% (95% CI 67% to 78%), but this did not meet the prespecified primary endpoint of greater than 70% of the lower bound of the 95% confidence interval, Min said.

However, Min emphasized that FFRCT was superior to CTA alone in all categories.

The researchers concluded that the results show the potential of FFRCT as a “promising” non-invasive tool to identify ischemia.

King added that despite not meeting the prespecified primary endpoint, “it’s an encouraging early study.”

This study was funded by HeartFlow

Min reported relationships with GE Healthcare and Philips Medical. Some of his co-authors reported relationships with GE Healthcare, Siemens Medical Systems, Lantheus Medical Imaging, Boston Scientific, Merck, Abbott Vascular, Medtronic, Cordis, Eli Lilly, Daiichi Sankyo, Bristol-Myers Squibb, and sanofi-aventis.

King reporeted relationships with Merck & Company, Wyeth Pharmaceuticals, Celonova Biosciences, and Northpoint Domain.

 

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