July 24, 2012

July 24, 2012 (Baltimore, Maryland) — Fractional flow reserve (FFR) measured with noninvasive coronary computed tomography angiography (CCTA) appears to be a cost-effective approach to guiding subsequent invasive angiography, a simulation study shows [1].

The study shows with "some simple assumptions that are quite reasonable" that FFR measurement based on CCTA (FFRct) has the potential to be "a winner" by reducing costs through lowering the number of PCI procedures. With fewer PCIs, "we actually may have better outcomes, because once you put those stents in or do other [invasive interventions], you may have problems down the line," coauthor Dr Mark Hlatky (Stanford University, CA) explained at the Society of Cardiovascular Computed Tomography 2012 Annual Scientific Meeting.

As reported by heartwire , the Fractional Flow Reserve vs Angiography for Guiding PCI in Patients with Multivessel Coronary Artery Disease (FAME) trial showed that routine measurement of FFR during PCI reduced mortality and MI--while also reducing the number of stents needed--by identifying flow-limiting lesions more accurately than angiography alone. The Diagnosis of Ischemia-Causing Stenoses Obtained via Noninvasive Fractional Flow Reserve (DISCOVER FLOW) trial showed that FFRct can identify coronary stenoses that cause ischemia without the invasive intervention of traditional catheter-based FFR measurement.

"How can we balance the potential for high sensitivity [of CCTA] and improve the specificity for lesions that are clinically important and potentially flow-limiting? Fractional flow reserve can reveal if a coronary stenosis is flow-limiting or not," Hlatky said. He also recalled his group's 2011 study that showed that CCTA can reduce follow-up testing in some patients when it shows no coronary disease, but because CCTA isn't very specific, CCTA testing can lead to more unnecessary costs, because it often flags clinically insignificant stenoses that do not need to be stented.

To find out if FFRct has the potential to improve outcomes and/or reduce the costs associated with unnecessary interventions, HeartFlow, the developer of the FFRct technology, sponsored a model study comparing the probable costs and outcomes of an FFRct-based strategy with other approaches to deciding which coronary lesions to treat.

Hlatky and colleagues used the data from the DISCOVER FLOW trial plus US cost data from the scientific literature to determine the one-year expected death and MI rates as well as the costs of three diagnostic strategies:

  • Invasive coronary angiography with PCI based on visual assessment of the angiogram.

  • CCTA followed by invasive angiography for lesions >50% in diameter followed by PCI based on visual inspection of the angiogram.

  • FFRct followed by invasive angiography and PCI for any lesions that have an FFRct ratio <0.8.

Analysis found that FFRct prior to an invasive evaluation would reduce the need for invasive angiography and PCI while cutting initial costs compared with CCTA or invasive angiography alone.

Projected Procedure Use, Costs, and One-Year MI/Mortality Rate for Each Diagnostic Strategy

Outcome Invasive angiography CCTA CCTA+FFRct
Invasive angiography procedures/100 patients 100 84 51
Vessels treated with PCI/100 patients 98 88 60
One-year death/MI rate (%) 2.7 2.6 2.3
Estimated initial treatment costs per patient ($) 11 500 10 393 7940


FFRct Is at Least in the Right Ballpark

Hlatky cautioned that this study is just a statistical model and now must be followed up with prospective studies that confirm that FFRct improves outcomes and/or saves money. "This is not a definitive evaluation. This is 'Gosh, this has a real promising strategy politically and economically,' " he said. "This clearly is just a simulation [to answer] an order-of-magnitude-estimation question, and what we need to do is study this prospectively and get actual data on these things."

The first important pivotal trial of FFRct, the 285-patient DEFACTO trial, is comparing FFRct with invasive FFR. Results from DEFACTO will presented during a "hotline" session at the European Society of Cardiology 2012 Congress on August 26 by Dr James Min (Cedars-Sinai Medical Center, Los Angeles, CA), Min said at the SCCT conference.

This research was sponsored by HeartFlow.