VERIFY-2 Compares FFR to New Coronary Lesion Assessment Measures

May 30, 2014—New measures of the severity of coronary artery blockages do not provide enough accuracy to guide treatment decisions, according to the results of the VERIFY-2 study presented as a late-breaking clinical trial at the Society for Cardiovascular Angiography and Interventions (SCAI) 2014 Scientific Sessions in Las Vegas, Nevada.

As noted in the SCAI announcement, fractional flow reserve (FFR) is a well-validated technique to measure pressure differences across coronary blockages. FFR-guided percutaneous coronary interventions (PCI) have shown improved outcomes compared to angiography alone. However, some interventional cardiologists have been hesitant to use FFR because it requires administration of the drug adenosine, which may not be well tolerated in some patients and adds time to the procedure. Interventional cardiologists can also use several other types of assessments to measure whether a blockage in the coronary artery is limiting blood flow to the heart to aid decisions before performing PCI.

According to SCAI, instantaneous wave-free ratio (iFR) is a new measure that assesses the pressure difference across a stenosis during a specific period of the cardiac cycle. It is measured at rest and does not require the administration of adenosine. Another index of stenosis severity is measuring resting distal coronary artery pressure/aortic pressure (Pd/Pa). Pd/Pa is measured at rest and without adenosine, but unlike iFR, it does not require any specific measurement software. 

The previous VERIFY and RESOLVE studies indicated that both iFR and Pd/Pa have similar levels of diagnostic accuracy (approximately 80%) when compared to FFR. The recent ADVISE II study demonstrated that a hybrid strategy using a combination of iFR and FFR correctly classified 94% of lesions compared to a strategy of using FFR in all patients, while avoiding the use of adenosine in two-thirds of the patients in the study.

Stuart Watkins, MD, commented in the SCAI press release, “The measurement of iFR has recently been introduced to aid interventional cardiologists in their assessment of coronary lesions without the need for adenosine. VERIFY-2 was designed to evaluate the accuracy of this measurement compared to Pd/Pa using FFR as the currently accepted gold standard.” Dr. Watkins is consultant cardiologist at the Golden Jubilee National Hospital in Glasgow, Scotland.

In the study presented at SCAI 2014, the investigators examined two hybrid assessment strategies: iFR-FFR with an adenosine zone of 0.86 to 0.93 and Pd/Pa-FFR with an adenosine zone of 0.87 to 0.94. A total of 97 patients with 120 coronary artery blockages were assessed. They found that 10.1% of lesions were misclassified using iFR-FFR, compared to 6.3% using Pd/Pa-FFR.

Next, the investigators assessed the accuracy of iFR and Pd/Pa compared to FFR using binary cut-off values of 0.9 for iFR and 0.92 for Pd/Pa. In this analysis, the use of iFR alone would result in inappropriate PCI in 8.3% of lesions and incomplete revascularization in another 10%. Using Pd/Pa alone would result in inappropriate PCI in 4.2% of lesions and incomplete revascularization in another 10.8%.

Both hybrid decision-making strategies and the use of binary cut-off values resulted in similar levels of lesion misclassification compared to FFR, concluded the investigators.

Dr. Watkins stated, “FFR remains the gold standard—we have concluded neither iFR nor Pd/Pa is sufficiently accurate to guide decisions on the need for revascularization. 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.”