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VERIFY-2: FFR remains gold standard for determining severity of stenosis
LAS VEGAS — Measurement of Pd/Pa or instantaneous wave-free ratio, whether used in binary algorithms or hybrid strategies that incorporate fractional flow reserve, are less accurate than fractional flow reserve alone for determining the severity of stenosis, according to new findings from the VERIFY-2 study.
“The measurement of [instantaneous wave-free ratio] has recently been introduced to aid interventional cardiologists in their assessment of coronary lesions without the need for adenosine,” Stuart Watkins, MD, consultant cardiologist at the Golden Jubilee National Hospital in Glasgow, Scotland, said in a press release. “VERIFY-2 was designed to evaluate the accuracy of this measurement compared to Pd/Pa using [fractional flow reserve] as the currently accepted gold standard.”
Stuart Watkins
Researchers assessed the accuracy of resting Pd/Pa and instantaneous wave-free ratio (iFR) in 97 patients with a total of 120 moderately severe coronary artery stenosis between September 2013 and March 2014. The results were presented at the Society for Cardiovascular Angiography and Interventions Scientific Sessions.
The cohort was 62% male. Hypertension (62%) and hypercholesterolemia (61%) were common at baseline. Two-thirds of patients had a family history of ischemic heart disease, 29% were smokers and 14% had diabetes. Accessed lesions were predominantly located in the left anterior descending branch (58%), with the remainder in the right coronary (19%), left circumflex (15%), left main stem (4%), and the obtuse marginal or diagonal branches (4%).
Pd/Pa and iFR measurements were obtained via the Volcano Prestige Wire (Volcano Corp). The mean resting Pd/Pa was 0.93 ± 0.06, mean iFR was 0.9 ± 0.08 and mean fractional flow reserve (FFR) was 0.82 ± 0.09.
The researchers compared the accuracy of FFR with a hybrid strategy involving both iFR and FFR, in which no adenosine or revascularization was administered if the iFR value was above 0.93, and revascularization with no adenosine was administered if iFR was below 0.86. A similar hybrid strategy involving Pd/Pa and FFR, with an adenosine zone of 0.87 to 0.94, was also assessed.
Use of an iFR/FFR hybrid strategy resulted in the misclassification of 10.1% of lesions outside of the zone, compared with a gold standard of FFR ≤0.8. The Pd/Pa and FFR hybrid strategy resulted in the misclassification of 6.3% of lesions outside the zone; the difference between the two hybrid approaches was not statistically significant (P=.42).
The researchers also conducted sensitivity analyses comparing iFR, Pd/Pa and FFR alone, using binary cut-offs of 0.9 for iFR and 0.92 for Pd/Pa. They observed a misclassification rate of 18.3% for iFR and 15% for Pd/Pa compared with FFR. (P=.49 for difference).
Additional analyses indicated an AUC of 0.873 (95% CI, 0.805-0.941) for iFR and 0.889 (95% CI, 0.82-0.958) for Pd/Pa compared with FFR ≤0.8. Lowering the FFR cutoff to 0.75 for comparison increased both values, which remained similar to one another (iFR: AUC=0.936, 95% CI, 0.886-0.986; Pd/Pa: AUC=0.946, 95% CI, 0.899-0.993).
“Hybrid decision-making strategies utilizing either Pd/Pa-FFR or iFR-FFR provide similar levels of misclassification,” Watkins said during a presentation.
Watkins concluded that neither index is sufficiently accurate to be used to guide the need to revascularization.
“FFR remains the gold standard,” he said in the press release. “Although these measures aren’t accurate enough to replace FFR, this study adds to our body of knowledge as we work to identify the most effective ways to measure lesion severity.” – by Adam Taliercio
For more information:
Watkins S. Late-Breaking Clinical Trials. Presented at: the Society for Cardiovascular Angiography and Interventions Scientific Sessions; May 28-31, 2014; Las Vegas.
Disclosure: Watkins reports no relevant financial disclosures.
Perspective
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I think that VERIFY-2 is a very important study. The value of iFR is being actively debated in the cardiology community. iFR or Pd/Pa measurement are appealing for several reasons: First, adenosine is very expensive, and secondly, it is time-consuming to administer. If you have a baseline number with iFR that you can be certain will be either positive or negative and you don't have to give adenosine, even if it only applies to some patients, it saves both time and cost. It would be ideal to just put a wire or catheter across a lesion and know immediately if you need to treat that lesion.
This study helps us in that it shows there is no benefit to iFR or Pd/Pa – that it's not accurate enough to completely exclude severe lesions – and so we still need to give adenosine. This will be looked at in ongoing clinical trials, but these results suggest that iFR is not be as accurate as we need it to be to correctly identify the physiologic significant of coronary obstructions.
