FFRCT Investigated as Screening Tool for Chest Pain in Proof-of-Concept Trial

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The primary study end point was the difference between clinical management guided by CTA alone and with the addition of FFRCT.
The primary study end point was the difference between clinical management guided by CTA alone and with the addition of FFRCT.

Computer tomography-derived fractional flow reserve (FFRCT) has the ability to significantly change the labeling of coronary artery disease (CAD) in patients with chest pain, according to research published in JACC: Cardiovascular Imaging.

Nicholas P. Curzen, BM, PhD, of University Hospital Southampton in the United Kingdom, and colleagues sought to determine if the routine availability of noninvasive FFRCT data would alter management strategy based solely on CT coronary angiography (CTA) data assessment.

Invasive CTA with FFR is currently the sole diagnostic test able to simultaneously evaluate anatomic and functional cardiac parameters. If noninvasive FFR in combination with CTA can define both ischemia and CAD, it may serve as an ideal screening test for at-risk patients presenting with angina.

Dr Curzen and colleagues chose 200 patients from the NXT (Analysis of Coronary Blood Flow Using CT Angiography: Next Steps) trial with stable chest pain who underwent CTA and had FFRCT data calculated. Patients were assigned to one of the following management plans depending on CTA results: optimal medical therapy, PCI, coronary artery bypass surgery, or more information required.

The primary study end point was the difference in management using CTA alone vs with the addition of FFRCT data. Secondary end points included what constituted “vessel significance” between CTA alone and the addition of FFRCT data. Researchers also wanted to compare the individual vessels deemed appropriate targets for coronary artery revascularization between the 2 diagnostic groups.

For the purposes of this study, a stenosis was considered “significant” if the diameter was narrowed by ≥50%, or by a FFR cut off of ≤0.80. Eight cases that were read as not having significant obstructive disease with CTA ended up having obstructive disease reported on the quantitative coronary angiography (QCA). Of those, 7 had a negative FFRCT.

On CTA, however, 94 cases were read as having significant obstructive disease that were then found to have no obstructive disease on QCA. Of those 94 patients, 57 had a negative FFRCT and 37 had a positive FFRCT.

Out of 577 vessels, FFRCT was ≤0.80 in 118. In 366 vessels found as having ≤50% diameter stenosis by CTA, FFRCT was ≤0.80 in 17. FFRCT was negative for ischemia in 13 of 44 vessels with diameter stenosis of >90% and in 38 of 83 vessels with diameter stenosis of 71% to 90%.

Furthermore, of the 87 patients originally assigned to PCI based on CTA alone, 26 (30%) were reallocated to optimal medical therapy on the basis that no ischemic lesion was detected by FFRCT. Target vessels for revascularization were changed in 16 of these patients, based on FFRCT. Of the 67 patients who were first assigned to optimal medical therapy based on CTA alone, 8 (12%) were reassigned to revascularization.

A change in treatment—defined as change in management category and change in target vessel—was made in nearly half the patient population (44%) as a result of the addition of FFR data.

“FFRCT is a novel diagnostic technique that allows derivation of FFR from CTA images without the need for further radiation or exposure to medication,” the authors concluded. “Previous studies in patients with stable chest pain have demonstrated promising diagnostic accuracy for the technique, which is significantly superior to that of CTA alone, presumably because CTA cannot accurately predict whether a lesion is associated with ischemia.”

Several important study limitations should be noted, including the use of data from an already completed clinical trial to test this proof of concept and the inability of the trial to account for patients who present with chest pain who were not candidates for CTA and/or FFRCT.

Disclosures: Dr Curzen has received unrestricted research grants from HeartFlow, Boston Scientific, St. Jude Medical, Haemonetics, and Medtronic; honoraria/speaker fees from HeartFlow, St. Jude Medical, and Haemonetics; and travel sponsorship from Biosensors, Lilly/D-S, and Abbott Vascular. Dr Nolan declares no disclosures. Dr Zaman has received unrestricted research grants from St. Jude Medical. Dr Norgaard has received unrestricted research grants from Edwards Lifesciences and Siemens. Dr Rajani has received consultancy fees from Edwards Lifesciences.

Reference

Curzen NP, Nolan J, Zaman AG, Norgaard BL, Rajani R. Does the routine availability of computer tomography-derived fractional flow reserve (FFRCT) influence management strategy of patients with stable chest pain compared to CT angiography alone? The FFRCT RIPCORD Study. JACC Cardiovasc Imag. 2016. doi: 10.1016/jcmg.2015.12.016.

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