Basal Stenosis Resistance
Another Adenosine-Free Contender for the Lesion Assessment Crown?
The notion that a hyperemia-free index can accurately determine the ischemic potential of coronary stenosis is conceptually appealing but fundamentally challenging and is literally at the heart of a current and heated controversy in coronary physiology.
Article see p 508
In this issue of Circulation: Cardiovascular Interventions, van de Hoef et al1 propose another adenosine-free contender to fractional flow reserve (FFR), the basal stenosis resistance (BSR). Translesional pressure and flow velocity were measured across 299 intermediate stenoses (55%±11% diameter narrowing) in 232 patients with one- or 2-vessel coronary artery disease studied from 1997 to 2006, expanding on their prior publication.2 Using 2 sensor guidewires and intracoronary boluses (20, 40 µg) of adenosine, they computed not only BSR (translesional gradient/basal average peak flow velocity), but also coronary flow velocity reserve (CFVR), FFR, and hyperemic stenosis resistance (HSR). The diagnostic performance of each index was determined by the area under the curve (AUC) from receiver operating characteristics against myocardial perfusion scintigraphy (MPS) and showed that BSR (AUC 0.77) was as good as FFR (AUC 0.77) and CFVR (AUC 0.75) but underperformed when compared with HSR (AUC 0.81). The authors thus propose that BSR is a potential replacement for FFR. This study raises several critical and confusing questions about how resting translesional pressure and flow can predict ischemia and what is a valid human ischemic standard.
Hyperemic and Basal Stenosis Resistance Versus FFR
Before looking at basal markers of lesion significance, we know that the hyperemic pressure gradient/flow ratio (HSR) and the hyperemic absolute pressure ratio (FFR) both measure translesional flow responses indicative of inducible ischemia. HSR normalizes the pressure gradient for flow (velocity) and is purportedly less impacted by the variability of the hyperemic flow response.3 In the authors’ 2002 report,2 the HSR also had a higher AUC (0.90) than FFR (AUC …