The Role of Coronary Physiology in Contemporary Percutaneous CoronaryInterventions

Fig. (1). Tools for the assessment of epicardial and microvascular resistance in the Catheterization laboratory. Abbreviations: CFR, Coronary Flow Reserve; cFFR, contrast FFR; DFR, diastolic hyperaemia-free ratio; dPR, diastolic pressure ratio; FFR, Fractional Flow Reserve; FFRangio angiography-derived FFR; HMR hyperaemic microvascular resistance index; iFR, instantaneous wave-free ratio; IMR, Index of Microcirculatory Resistance; IMRangio, angiography-derived index of microcirculatory resistance; A-IMR, Angio-based Index of Microcirculatory Resistance, IVUS-FFR, Intravascular Ultrasound derived FFR; OCT-FFR, Optical Coherence Tomography derived FFR; Pa, aortic pressure; Pd, distal pressure; QFR, Quantitative Flow Ratio; RFR, Resting Full-cycle Ratio; RRR, Resistive Reserve Ratio; vFFR, virtual FFR. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (3). Case example of disagreement between iFR and FFR. Coronary angiogram of a 55-year old gentleman presenting with stable angina, showing a moderate lesion on the distal segment of the right coronary artery (asterisk). Invasive pressure-wire assessment was performed both in resting condition using iFR and hyperaemia using FFR. Discordant values were obtained: iFR was 0,93, above the ischemic threshold; FFR was 0,74, suggesting myocardial ischemia. Based on clinical presentation, angioplasty was performed. During follow-up, no further recurrence of symptoms was reported. Abbreviations: iFR, instantaneous wave Free Ratio; FFR, Fractional Flow Reserve. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (2). Explanatory case of comprehensive physiological assessment of both the epicardial and microvascular resistance obtained by different complementary tools in the catheterization laboratory. In Panel A from left to right is represented the physiological assessment of an angiographic intermediate stenosis on the mid segment of the LAD with different approaches; 3D quantitative coronary analysis and subsequent QFR computation was 0,78); Resting full cycle ratio (RFR), a non-hyperaemic full cycle pressure-wire based index, was 0,79; hyperemic FFR pull-back confirmed a significant step up located in the mid segment of LAD. In Panel B the previous measurements were repeated after PCI: QFR was 0.99, RFR was 0.96 and FFR was 0.96 suggesting non-significant residual ischemia. Optical coherence tomography of the LAD was performed in order to assess the post stenting result and the computed optical flow ratio (OFR) derived from 3-dimensional reconstructed artery was 0.96. Microvascular assessment was also performed after PCI measured by thermodilution and derived from angiography: Coronary Flow Reserve (CFRthermo) was 1,4; Index of microcirculatory resistance (IMR) was 16 and RRR was 2. Based…

Fig. (4). Case example of Quantitative Flow Ratio (QFR). Coronary angiography shows a diffuse disease on the right coronary artery. FFR measured by pressure wire at asterisk was 0,75. Three-dimensional reconstruction of coronary artery and computation of QFR was 0,79. Abbreviations: FFR, fractional flow reserve; FS indicates foreshortening; QFR, quantitative flow ratio. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (5). Case example of vessel fractional flow reserve (vFFR). Coronary angiography shows a left anterior descending lesion. FFR measured by pressure wire at asterisk was 0.72. Three-dimensional reconstruction of coronary artery and computation of vFFR, using 2 angiographic projection with at least 30 degrees apart and invasively measured aortic root pressure showed a value of 0.73. Abbreviations: FFR, fractional flow reserve; vFFR, vessel fractional flow reserve; CRA indicates cranial, CAU indicates caudal, RAO, right anterior oblique; and RAO, right anterior oblique. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (6). Case example of optical flow ratio (OFR). Coronary angiography shows a left anterior descending lesion with a minimal lumen area (MLA) by OCT of 2.36 mm2. FFR measured by pressure wire at asterisk was 0,64. The computed optical flow ratio (OFR) value was 0,64, which was color-coded and superimposed on the 3-dimensional reconstructed artery (OctPlus v. 2.0, Pulse medical imaging technology. Abbreviations: FFR, Fractional Flow Reserve; MLA, Minimal Lumen Area; OCT, Optical Coherence Tomography; OFR, Optical Flow Ratio. (A higher resolution / colour version of this figure is available in the electronic copy of the article).

Fig. (7). Physiological assessment of microvascular resistance. Explanatory case showing a comprehensive assessment of coronary physiology in a 55-year old lady complaining of chest pain. Coronary angiogram revealed the presence of mild disease on the left anterior descending artery. Functional assessment of epicardial resistance assessed by FFR was inside normal range (FFR: 0.95). The assessment of microvascular compartment, performed using a pressure wire coupled with thermodilution, demonstrated the presence of increase microvascular resistance (IMR: 26, RRR 2.1) and a reduction of CFR (CFR 1.3). Microvascular angina was diagnosed, and appropriate therapy was started. Abbreviations: CFR, Coronary Flow Reserve; FFR, Fractional Flow Reserve; IMR, Index of Microcirculatory Resistance; RRR, Resistive Reserve Ratio. (A higher resolution / colour version of this figure is available in the electronic copy of the article).