J Cardiovasc Interv.  2023 Jul;2(3):152-160. 10.54912/jci.2022.0031.

Clinical Implications of Non-Hyperemic Pressure Ratios

• Jang HJ

• KMID: 2560942
• DOI: http://doi.org/10.54912/jci.2022.0031

Abstract

Fractional flow reserve (FFR) is a representative physiological index that evaluates whether specific coronary artery stenosis causes myocardial ischemia under maximal hyperemic induction. Although recent guidelines recommend using FFR supported by a large body of physiological evidence, the adoption rate is still low in the clinical field. This facilitates the development of non-hyperemic pressure ratios (NHPRs) that can perform a hemodynamic evaluation of coronary stenosis with reduced discomfort, lower cost, and shorter procedural time by avoiding maximal hyperemic induction. Instantaneous wave-free ratio (iFR), introduced as a substitute for FFR, proved non-inferior to FFR and is eventually recommended by the newest guidelines along with FFR in the physiologic evaluation of intermediate coronary lesions. Currently, iFR is striking its own path such as iFR coregistration in tandem lesion revascularization. However, experimental data to support wave-free period (WFP) theory, the key concept of iFR, are lacking, providing a reason for developing various new NHPRs against the absoluteness of WFP. Diastolic pressure ratio, diastolic hyperemia-free ratio, and resting full-cycle ratio showed no difference with iFR and cutoff values of 0.89 for predicting FFR of 0.8 are identical to that of iFR, resulting in widening of the NHPR options in the clinical field. On the other hand, iFR/FFR discordance is consistently observed in 15–20% of cases and the optimal treatment strategy has yet to be determined. Discordance is intrinsic among each NHPRs and is believed to occur because the definition of the resting state is not settled. As non-invasive physiological assessments such as computed tomography-derived FFR and quantitative flow ratio improve, further evidence is required to tailor certain NHPRs to specific patient and clinical scenarios in order to maximize their benefits.

Keyword

Coronary stenosis; Myocardial ischemia; Fractional flow reserve, Myocardial; Arterial pressure