PARIS, FRANCE — The stress test, in all its iterations, could find competition for the evaluation of patients with chest pain who may or may not be good candidates for invasive coronary angiography, say proponents of CT angiography (CTA) that incorporates fractional flow reserve (FFA) assessment. In a virtual test run of using such FFR-CT at that stage of the screening process, such imaging of both coronary anatomy and ischemic potential led to reallocation of treatment assignment based on CTA alone in 36% of cases[1].

In other words, in the comparison of two entirely noninvasive screening strategies, there was substantial mismatch in the take-home message on treatment decision based solely on visually apparent lesion severity vs visual severity plus estimated lesion functional impact.

In some ways, the study, based on three interventionalists' reading of scans from 200 consecutive stable patients with chest pain of unknown origin, called FFRCT RIPCORD, was a noninvasive reflection of the similarly sized prior RIPCORD study of treatment allocation based on two catheter-based tests, FFR and standard angiography. That study's conclusions in the invasive arena—that adding FFR sharpens treatment decisions—were similar to those of the current study of solely noninvasive imaging.

The functional impact of angiographically tight coronary lesions may be small, while it can be severe for moderate stenoses—long a challenge in invasive cardiology: which lesions will PCI serve best? Treadmill stress testing can help identify functionally significant stenoses, but the correlation is limited and the tests are entirely separate. FFR-CT combines both into one noninvasive scan.

 
This could represent a complete change in the way we assess patients and eliminate some of the tests that we do now.
 

The potential effect of FFR-CT on patients in the current study was substantial: 12% of patients who would have been assigned to just optimal medical therapy (OMT) based on standard CTA would been sent to revascularization instead based on FFR-CT results, reported Dr Nick Curzen (University Hospital Southampton, UK) here at EuroPCR 2015. And 30% of those who would have gone to PCI based on CTA alone were reassigned, based on FFR-CT, to only OMT. Even 18% allocated to PCI based on CTA had their target vessel switched to another based on FFR-CT.

Curzen, who is cautious about overinterpreting the study's findings pending prospective randomized trials, nonetheless seems passionate about the potential of FFR-CT. "This could represent a complete change in the way we assess patients and eliminate some of the tests that we do now," he told heartwire from Medscape.

The outpatient imaging procedure "could be used as a one-stop method of refining the diagnosis and triage of patients," he said, and obviate many exercise-ECG tests and other stress tests. It could also keep many people who might now be sent to invasive angiography or intervention "from needing to ever have the risk of going to the cath lab." But, he emphasized, "it's for stable patients at the moment."

In FFRCT RIPCORD, the three interpreters reviewed conventional CTA scans for the 200 patients and then, by consensus, decided on a management plan based on the anatomic appearance of lesions, according to Curzen. They allocated each patient to receive OMT alone, PCI plus OMT, or CABG plus OMT or designated them as "more information required." Then the FFR data component of the scans was added to imaging in each case, and the process was repeated based on FFR-CT, with reallocation to a management plan consisting of OMT alone or with PCI or CABG.

Change in Management Recommendations Based on CT Angiography Alone and After Disclosure of FFR-CT Data in 200 Patients

End points CT angiography alone (% of cohort) CT angiography plus FFR-CT (% of cohort)* Change
More data needed 19.0 0  
OMT 33.5 56.5 +23
PCI+OMT 43.5 39.0 -5
CABG+OMT 4.0 4.5 +0.5
OMT=optimal medical therapy
FFR-CT=fractional flow reserve at computed tomography
*reallocation P<0.001

Curzen observed for heartwire that direct functional assessment of coronary lesions has been available for years, but uptake in practice has been limited. The data favoring invasive FFR as a complement to diagnostic angiography "is absolutely overwhelming, but still it is used in only 18% of interventional cases around the world. One of the reasons for the reluctance in take-up is that it's complex and costs money. If we could replace that to some extent with noninvasive FFR, it would take away some people's objections that it's complex to do and time-consuming."

FFRCT RIPCORD was funded by HeartFlow. Curzen discloses receiving honoraria from HeartFlow, St Jude Medical, and Volcano; and institutional grants or research support from Boston Scientific, Haemonetics, HeartFlow, and Medtronic.

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