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. 2023 Jun 19;19(3):203-221.
doi: 10.4244/EIJ-D-22-00969.

Functional coronary angiography for the assessment of the epicardial vessels and the microcirculation

Daniel Faria  1   2 , Breda Hennessey  1 , Asad Shabbir  1 , Hernán Mejía-Rentería  1 , Lin Wang  1 , Joo Myung Lee  3 , Hitoshi Matsuo  4 , Simone Biscaglia  5 , Bon-Kwon Koo  6 , Bo Xu  7 , Sérgio Baptista  2   8 , Nievez Gonzalo  1 , Javier Escaned  1
Affiliations

Functional coronary angiography for the assessment of the epicardial vessels and the microcirculation

Daniel Faria et al. EuroIntervention. .

Abstract

Over the last decade, steady progress has been made in the ability to assess coronary stenosis relevance by merging computerised analyses of angiograms with fluid dynamic modelling. The new field of functional coronary angiography (FCA) has attracted the attention of both clinical and interventional cardiologists as it anticipates a new era of facilitated physiological assessment of coronary artery disease, without the need for intracoronary instrumentation or vasodilator drug administration, and an increased adoption of ischaemia-driven revascularisation. This state-of-the-art review performs a deep dive into the foundations and rationale behind FCA indices derived from either invasive or computed angiograms. We discuss the currently available FCA systems, the evidence supporting their use, and the specific clinical scenarios in which FCA might facilitate patient management. Finally, the rapidly growing application of FCA to the diagnosis of coronary microvascular dysfunction is discussed. Overall, we aim to provide a state-of-the-art review not only to digest the achievements made so far in FCA, but also to enable the reader to follow the many publications and developments in this field that will likely take place in years to come.

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Conflict of interest statement

H.Mejía-Rentería has received speaker fees from Abbott Vascular, Boston Scientific, and Philips Healthcare. J.M.Lee received aresearch grant from Abbott Vascular and Philips/Volcano. H.Matsuo has received speaker fees from Philips, Boston Scientific, Abbott Vascular, and Zeon Medical. S.Baptista has received personal fees from Abbott, Boston Scientific, and HeartFlow. N.Gonzalo has received consultancy and speaker fees from Abbott Vascular, Boston Scientific, Philips/Volcano, and Shockwave Medical. J.Escaned has received speaker and/or advisory board member fees from Abbott Vascular, Boston Scientific, Medis, and Philips. The other authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1. Timeline of the evolution of non-invasive coronary physiology and the respective landmark studies.
CAAS vFFR: vessel fractional flow reserve; caFFR: computational pressure-flow dynamics derived FFR; FFR: fractional flow reserve; FFRangio: angiography-derived FFR; FFRCT: computed tomography-derived FFR; QFR: quantitative flow ratio; vFFR: virtual fractional flow reserve
Figure 2
Figure 2. Steps for obtaining a functional coronary imaging index.
1) Standard invasive coronary angiography or computed tomography angiography data are obtained. A quantitative 3-dimensional anatomical model is generated. 2) A physiological model of the coronary microcirculation is obtained from patient-specific data following specific principles: the resting coronary flow is proportional to the subtended myocardial mass; the microvascular resistance is inversely correlated with vessel size; the microvascular resistance is reduced during maximal hyperaemia. 3) Physical laws of fluid dynamics are applied to compute coronary blood flow, solving the Navier-Stokes equations or simplified equations. 4) The chosen functional index is calculated throughout the coronary artery. FFRCT: computed tomography-derived fractional flow reserve; QFR: quantitative flow ratio; vFFR: virtual fractional flow reserve.
Figure 3
Figure 3. Contrast QFR for the left anterior descending artery.
Coronary angiography showed an intermediate lesion in mid-left anterior descending artery. Contrast QFR in the same vessel was positive for significant functional ischaemia (0.70). Virtual angioplasty in a small segment (between the green markers) showed an expected final QFR of 0.84 after stenting. MLD: minimum lumen diameter; PCI: percutaneous coronary intervention; QFR: quantitative flow ratio; %D: % diameter
Figure 4
Figure 4. Coronary computed tomography-derived fractional flow reserve.
A) CCTA of the LAD artery is shown. Arrowhead indicates a calcified plaque in the middle segment with 50% diameter stenosis. B) A quantitative 3D colour-coded anatomical model is generated. C) FFRCT is calculated throughout the coronary tree. The FFRCT value of 0.63 in the distal LAD artery suggests the presence of a functionally significant stenosis after the emergence of the first diagonal branch. Courtesy of Dr Joo Myung Lee. CCTA: coronary computed tomography angiography; FFR: fractional flow reserve; FFRCT: coronary computed tomography-derived FFR; LAD: left anterior descending
Figure 5
Figure 5. Utilisation of FCA in clinical practice.
Decision-making algorithm for the usage of FCA in pre- and post-PCI settings. CCTA: coronary computed tomography angiography; FCA: functional coronary angiography; FFRCT: computed tomography-derived fractional flow reserve; LM: left main; PCI: percutaneous coronary intervention; TIMI: Thrombolysis in Myocardial Infarction
Figure 6
Figure 6. Simulation of PCI results using FFRCT.
A) CT-based functional coronary angiography showing a flow-limiting stenosis in the mid-segment of the left anterior descending artery. B) Simulation of PCI results after choosing the target segment to treat and C) expected haemodynamic results after achieving revascularisation. FFRCT: coronary computed tomography derived fractional flow reserve; PCI: percutaneous coronary intervention
Figure 7
Figure 7. Establishing the cause of suboptimal functional PCI results with QFR.
The white brackets indicate the stented segment. The red arrows point to the major QFR drop during pullback. A) Focal intra-stent drop. B) Combined intra-stent focal drop and distal diffuse disease. C) Distal focal drop outside the stent. D) Diffuse disease. Courtesy of Dr Simone Biscaglia. PCI: percutaneous coronary intervention; QFR: quantitative flow ratio
Figure 8
Figure 8. Derivation of coronary microvascular resistance from FCA.
A) Steps and formulas for calculating the hyperaemic index of coronary microvascular resistance without the need for guidewires or hyperaemic drug administration. B) Invasive assessment of IMR by thermodilution-derived coronary flow curves. angio-IMR: wire- and adenosine- free IMR; DS: diameter stenosis; FCA: functional coronary angiography; IMR: index of microvascular resistance; IMRcorr: IMR adjusted by Young’s formula; QFR: quantitative flow ratio
Central illustration
Central illustration. Current commercially available functional indices based on invasive coronary angiography.
The columns from left to right show user interface display after index calculation; number of angiographic projections needed; need for mean aortic pressure input; capacity to provide microcirculatory resistance evaluation; simultaneous side branch physiological interrogation; and the quality and quantity of published evidence. Colour code: green=advantage; yellow: amenable; red=disadvantage. CAAS vFFR: vessel fractional flow reserve; caFFR: computational pressure-flow dynamics derived FFR; FFR: fractional flow reserve; FFRangio: angiography-derived FFR; QFR: quantitative flow ratio; μQFR: Murray law-based QFR;
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