Cardiovascular Intervention and Therapeutics | 2019
Discordance of intracoronary pressure-based indices in severe angiographic stenosis: are we missing the flow?
Abstract
Resting and hyperemia pressure-based indices are guideline recommended for the assessment of intermediate coronary artery stenoses. Discordance between resting and hyperemia-dependent indices has been observed in around 20% of cases which may create uncertainty in interpretation [1]. We report a case of an 80-year-old diabetic male with class III angina, normal left ventricular function and regional motion who underwent percutaneous coronary intervention (PCI) to a severe mid-right coronary artery (RCA) stenosis (Fig. 1a). Stenting was physiology-guided as mandated by research study protocol. Quantitative coronary angiography demonstrated an 82% diameter stenosis. Pre-PCI fractional flow reserve (FFR; with intravenous adenosine, 140 μg/kg per min) was 0.67 (Fig. 1c), resting full-cycle ratio (RFR) was 0.91 and whole-cycle Pd/Pa and instantaneous wave-free ratio (iFR) were 0.96 (Fig. 1d), as derived retrospectively using previously described methods [2]. Revascularisation was performed using a 3.5 × 18 mm everolimus-eluting stent (Fig. 1b) as guided by the abnormal FFR value. Post-PCI FFR, RFR, whole-cycle Pd/Pa and iFR were all 1.0. During both preand post-PCI pressure wire pullbacks, there was no significant signal drift. The patient was symptom-free at discharge and at 1-month follow-up. This case highlights that the presence of discordance between hyperemic and resting indices may occur even in severe angiographic stenoses. Notably such lesions were not included in the DEFINE-FLAIR and iFR-SWEDEHEART trials which evaluated the prognostic significance of resting indices in intermediate lesions [3]. As such the diagnostic utility of resting indices to defer PCI in severe stenoses is not well established. Recent evidence suggests that iFR better relates to coronary flow reserve than FFR, with further data suggesting lower event rates for intermediate lesions deferred in the left anterior descending artery using iFR compared to FFR [4]. There is currently paucity of outcome data on whether this may hold true in discordant angiographically severe stenoses with normal resting indices. While such lesions are not usually subject to functional assessment in clinical practice, this case highlights the difficulty in interpretation in discordant cases and may caution the deferral of PCI based on normal resting indices in angiographically severe stenoses.