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Background: Coronary flow reserve (CFR) and microvascular resistance reserve (MRR) can, in principle, be derived by any method assessing coronary flow., Objectives: The aim of this study was to compare CFR and MRR as derived by continuous (CFR cont and MRR cont ) and bolus thermodilution (CFR bolus and MRR bolus )., Methods: A total of 175 patients with chest pain and nonobstructive coronary artery disease were studied. Bolus and continuous thermodilution measurements were performed in the left anterior descending coronary artery. MRR was calculated as the ratio of CFR to fractional flow reserve and corrected for changes in systemic pressure. In 102 patients, bolus and continuous thermodilution measurements were performed in duplicate to assess test-retest reliability., Results: Mean CFR bolus was higher than CFR cont (3.47 ± 1.42 and 2.67 ± 0.81 [P < 0.001], mean difference 0.80, upper limit of agreement 3.92, lower limit of agreement -2.32). Mean MRR bolus was also higher than MRR cont (4.40 ± 1.99 and 3.22 ± 1.02 [P < 0.001], mean difference 1.2, upper limit of agreement 5.08, lower limit of agreement -2.71). The correlation between CFR and MRR values obtained using both methods was significant but weak (CFR, r = 0.28 [95% CI: 0.14-0.41]; MRR, r = 0.26 [95% CI: 0.16-0.39]; P < 0.001 for both). The precision of both CFR and MRR was higher when assessed using continuous thermodilution compared with bolus thermodilution (repeatability coefficients of 0.89 and 2.79 for CFR cont and CFR bolus , respectively, and 1.01 and 3.05 for MRR cont and MRR bolus , respectively)., Conclusions: Compared with bolus thermodilution, continuous thermodilution yields lower values of CFR and MRR accompanied by an almost 3-fold reduction of the variability in the measured results., Competing Interests: Funding Support and Author Disclosures Drs Paolisso and Esposito are supported by a research grant from the CardioPaTh PhD Program. Dr Barbato has received speaker fees from Abbott Vascular, Boston Scientific, and GE Healthcare. Dr Collet has received research grants from Biosensors, GE Healthcare, Medis Medical Imaging, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow, and Abbott Vascular; and has received consultancy fees from HeartFlow, Opsens, Pie Medical Imaging, Abbott Vascular, and Philips. Dr De Bruyne has institutional consulting relationships with Boston Scientific, Abbott Vascular, CathWorks, Siemens, GE Healthcare, and Coroventis Research; has received institutional research grants from Abbott Vascular, Coroventis Research, CathWorks, and Boston Scientific; and has minor equity holdings in Philips, Siemens, GE Healthcare, Edwards Lifesciences, HeartFlow, Opsens, Celiad, Bayer, and Sanofi. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Low fractional flow reserve (FFR) after percutaneous coronary intervention (PCI) has been associated with adverse clinical outcomes. Hitherto, this assessment has been independent of the epicardial vessel interrogated., Objectives: This study sought to assess the predictive capacity of post-PCI FFR for target vessel failure (TVF) stratified by coronary artery., Methods: We performed a systematic review and individual patient-level data meta-analysis of randomized clinical trials and observational studies with protocol-recommended post-PCI FFR assessment. The difference in post-PCI FFR between left anterior descending (LAD) and non-LAD arteries was assessed using a random-effect models meta-analysis of mean differences. TVF was defined as a composite of cardiac death, target vessel myocardial infarction, and clinically driven target vessel revascularization., Results: Overall, 3,336 vessels (n = 2,760 patients) with post-PCI FFR measurements were included in 9 studies. The weighted mean post-PCI FFR was 0.89 (95% CI: 0.87-0.90) and differed significantly between coronary vessels (LAD = 0.86; 95% CI: 0.85 to 0.88 vs non-LAD = 0.93; 95% CI: 0.91-0.94; P < 0.001). Post-PCI FFR was an independent predictor of TVF, with its risk increasing by 52% for every reduction of 0.10 FFR units, and this was mainly driven by TVR. The predictive capacity for TVF was poor for LAD arteries (AUC: 0.52; 95% CI: 0.47-0.58) and moderate for non-LAD arteries (AUC: 0.66; 95% CI: 0.59-0.73; LAD vs non-LAD arteries, P = 0.005)., Conclusions: The LAD is associated with a lower post-PCI FFR than non-LAD arteries, emphasizing the importance of interpreting post-PCI FFR on a vessel-specific basis. Although a higher post-PCI FFR was associated with improved prognosis, its predictive capacity for events differs between the LAD and non-LAD arteries, being poor in the LAD and moderate in the non-LAD vessels., Competing Interests: Funding Support and Author Disclosures Dr Collet received research grants from Biosensors, HeartFlow Inc, Abbott Vascular, Insight Lifetech, GE Healthcare, Siemens and Shockwave Medical. Dr Johnson has received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; has received significant institutional research support from St. Jude Medical (CONTRAST, NCT02184117) and Philips Volcano (DEFINE-FLOW, NCT02328820) for studies using intracoronary pressure and flow sensors; has an institutional licensing agreement with Boston Scientific for the smart-minimum FFR algorithm commercialized under 510(k) K191008; and has pending patents on diagnostic methods for quantifying aortic stenosis and TAVI physiology and also algorithms to correct pressure tracings from fluid-filled catheters. Dr Mizukami has received consultancy fees from Zeon Medical. Dr Fearon receives institutional research support from Abbott Vascular, Boston Scientific, Medtronic, and Edwards Lifesciences; he has a consulting relationship with CathWorks and Siemens; and he owns minor stock options in HeartFlow. Dr Berry receives research funding from the British Heart Foundation grant (RE/18/6134217); and is employed by the University of Glasgow, which holds consultancy and research agreements for his work with Abbott Vascular, AstraZeneca, Boehringer Ingelheim, Causeway Therapeutics, Coroventis, Genentech, GlaxoSmithKline, HeartFlow, Menarini, Neovasc, Siemens Healthcare, and Valo Health. Dr Sonck is supported by a grant provided by the CardioPath PhD program. Dr Collison has received honoraria/speaker fees from Abbott. Dr Koo has received an institutional research grant from St. Jude Medical (Abbott Vascular) and Philips Volcano. Dr Meneveau has received consultancy and speaker fees from Abbott Vascular, Edwards Lifesciences, Terumo, Boston Scientific, Bayer Healthcare, BMS-Pfizer, Boehringer, and AstraZeneca. Dr Oldroyd is an employee of Biosensors International. Dr Leipsic is a consultant for and holds stock options in Circle CVI and HeartFlow; and has a research grant from GE Healthcare. Dr Taylor is an employee of HeartFlow Inc. Dr Ko has received consultancy fees from Abbott Vascular and Medtronic; and has received research support from Canon Medical. Dr Perera has received research grant support from Abbott Vascular, HeartFlow, and Philips. Dr Leone received consultant fees and honoraria for lectures in sponsored symposia with Abbott Vascular and Bracco Imaging/ACIST Medical. Dr Matsuo has received consultancy fees from Zeon Medical; and has received speaker fees from Abbott Vascular Japan, Philips, and Boston Scientific. Dr Amabile reports consulting/proctoring fees from Abbott Vascular, Boston Scientific, and Shockwave Medical; and has received an institutional research grant from Abbott Vascular and Boston Scientific. Dr Piróth has received consultancy and speaker fees from Abbott Vascular, Opsens, and Boston Scientific. Dr Toth has received consultancy fees and research support from Abbott, Biotronik, Medtronic, and Terumo. Dr Ihdayhid reports receiving consulting honorarium from Abbott Medical, Edwards Lifesciences, Boston Scientific, Artrya Pty Ltd (including equity interest). Dr West is an employee of Abbott Vascular. Dr Munhoz is supported with a PhD grant from CardioPath. Dr Barbato has received speaker fees from Abbott and Boston Scientific. Dr Engstrøm has received consultancy and speaker fees from Abbott Vascular, Novo Nordisk, and Bayer AS. Dr Escaned is supported by the Intensification of Research Activity project INT22/00088 from Spanish Instituto de Salud Carlos III, and served as speaker and advisory board member for Abbott and Philips. Dr Ali has received institutional grant support Abbott, Abiomed, ACIST Medical, Amgen, Boston Scientific, Cathworks, Canon, Conavi, Heartflow, Inari, Medtronic Inc, National Institute of Health, Nipro, Opsens Medical, Medis, Philips, Shockwave, Siemens, Spectrawave, Teleflex; and consulting fees from Abiomed, AstraZeneca, Boston Scientific, Cathworks, Opsens, Philips, Shockwave and equity in Elucid, Lifelink, Spectrawave, Shockwave, VitalConnect. Dr Kern has received speaker fees from Abbott, ACIST Medical, Boston Scientific, Opsens, and Philips. Dr Pijls has received research grants from Abbott and Hexacath and consultancy fees from Abbott, GE, Philips, and HeartFlow and have equity in GE, Philips, and Heartflow. Dr De Bruyne has received institutional consulting fees from Abbott Vascular, Boston Scientific, Siemens, and GE; has received institutional grant support from Abbott Vascular, Boston Scientific, Biotronic, CathWorks, Pie Medical, and HeartFlow; and holds minor equities in Philips, Siemens, GE, Bayer, HeartFlow, Edwards Lifesciences, and Ceyliad. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: An increase in fractional flow reserve (FFR) after percutaneous coronary intervention (PCI) is associated with improvement in angina. Coronary artery disease (CAD) patterns (focal vs diffuse) influence the FFR change after stenting and may predict angina relief., Objectives: The aim of this study was to investigate the differential improvement in patient-reported outcomes after PCI in focal and diffuse CAD as defined by the pullback pressure gradient (PPG)., Methods: This is a subanalysis of the TARGET-FFR (Trial of Angiography vs. pressure-Ratio-Guided Enhancement Techniques-Fractional Flow Reserve) randomized clinical trial. The 7-item Seattle Angina Questionnaire (SAQ-7) was administered at baseline and 3 months after PCI. The PPG index was calculated from manual pre-PCI FFR pullbacks. The median PPG value was used to define focal and diffuse CAD. Residual angina was defined as an SAQ-7 score <100., Results: A total of 103 patients were analyzed. There were no differences in the baseline characteristics between patients with focal and diffuse CAD. Focal disease had larger increases in FFR after PCI than patients with diffuse disease (0.30 ± 0.14 vs 0.19 ± 0.12; P < 0.001). Patients with focal disease who underwent PCI for focal CAD had significantly higher SAQ-7 summary scores at follow-up than those with diffuse CAD (87.1 ± 20.3 vs 75.6 ± 24.4; mean difference = 11.5 [95% CI: 2.8-20.3]; P = 0.01). After PCI, residual angina was present in 39.8% but was significantly less in those with treated focal CAD (27.5% vs 51.9%; P = 0.020)., Conclusions: Residual angina after PCI was almost twice as common in patients with a low PPG (diffuse disease), whereas patients with a high PPG (focal disease) reported greater improvement in angina and quality of life. The baseline pattern of CAD can predict the likelihood of angina relief. (Trial of Angiography vs. pressure-Ratio-Guided Enhancement Techniques-Fractional Flow Reserve [TARGET-FFR]; NCT03259815)., Competing Interests: Funding Support and Author Disclosures Dr Collet has received research grants from Biosensor, Coroventis Research, Medis Medical Imaging, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow, and Abbott Vascular; and has received consultancy fees from HeartFlow, OpSens, Abbott Vascular, and Philips Volcano. Dr Collison has received consultancy and speaker fees from Abbott. Dr Munhoz has received research grants provided by the Cardiopath PhD program. Dr Berry is employed by the University of Glasgow, which holds consultancy and research agreements for his work with Abbott Vascular, AstraZeneca, Auxilius Pharma, Boehringer Ingelheim, Causeway Therapeutics, Coroventis, Genentech, GlaxoSmithKline, HeartFlow, Menarini, Neovasc, Siemens Healthcare, and Valo Health; and has received research funding from the British Heart Foundation grant (RE/18/6134217) and EPSRC (EP/R511705/1, EP/S030875/1). Dr De Bruyne has received consultancy fees from Boston Scientific and Abbott Vascular; has received research grants from Coroventis Research, Pie Medical Imaging, CathWorks, Boston Scientific, Siemens, HeartFlow, and Abbott Vascular; and owns equity in Siemens, GE, Philips, HeartFlow, Edwards Life Sciences, Bayer, Sanofi, and Celyad. Dr Oldroyd is an employee of Biosensors International. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Coronary microvascular dysfunction is a highly prevalent condition in both obstructive and nonobstructive coronary artery disease. Intracoronary thermodilution is a promising technique to investigate coronary microvascular (dys)function in vivo and to assess its most important metric: microvascular resistance. Here, the authors provide a practical review of bolus and continuous thermodilution for the measurement of coronary flow and microvascular resistance. The authors describe the basic principles of indicator-dilution theory and of coronary thermodilution and detail the practicalities of their application in the catheterization laboratory. Finally, the authors discuss contemporary clinical applications of coronary thermodilution-based microvascular assessment in humans and future perspectives., Competing Interests: Funding Support and Author Disclosures Drs. Kodeboina, Fournier, Di Gioia, and Sonk are supported by a research grant from CardioPaTh. Dr. Di Gioia is supported by the STAR program of Compagnia di San Paolo. Dr. Collet has received institutional consultancy fees from HeartFlow and Philips Volcano. Dr. van ’t Veer has received speaker fees from Abbott. Dr. Pijls has received institutional research grants from Abbott and Hexacath; has received consultancy fees from Abbott, Opsens, and GE; and holds minor equity positions in Philips, ASML, and HeartFlow. Dr. De Bruyne has received institutional consulting fees from Abbott Vascular, Boston Scientific, Opsens, and Siemens; has received institutional grant support from Abbott Vascular, Boston Scientific, Biotronik, and Medtronic; and holds equity positions in Philips, Siemens, GE, Bayer, HeartFlow, Edwards Lifesciences, and Ceyliad. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021. Published by Elsevier Inc.)

Objectives: The aim of this study was to investigate the accuracy of pre-percutaneous coronary intervention (PCI) predicted nonhyperemic pressure ratios (NHPRs) with actual post-PCI NHPRs and to assess the efficacy of PCI strategy using pre-PCI NHPR pullback., Background: Predicting the functional results of PCI is feasible using pre-PCI longitudinal vessel interrogation with the instantaneous wave-free ratio (iFR), a pressure-based, adenosine-free NHPR. However, the reliability of novel NHPRs (resting full-cycle ratio [RFR] and diastolic pressure ratio [dPR]) for this purpose remains uncertain., Methods: In this prospective, multicenter, randomized controlled trial, vessels were randomly assigned to receive pre-PCI iFR, RFR, or dPR pullback (50 vessels each). The pre-PCI predicted NHPRs were compared with actual NHPRs after contemporary PCI using intravascular imaging. The number and the total length of treated lesions were compared between NHPR pullback-guided and angiography-guided strategies., Results: The predicted NHPRs were strongly correlated with actual NHPRs: iFR, r = 0.83 (95% confidence interval: 0.72 to 0.90; p < 0.001); RFR, r = 0.84 (95% confidence interval: 0.73 to 0.91; p < 0.001), and dPR, r = 0.84 (95% confidence interval: 0.73 to 0.91; p < 0.001). The number and the total length of treated lesions were lower with the NHPR pullback strategy than with the angiography-guided strategy, leading to physiological improvement., Conclusions: Predicting functional PCI results on the basis of pre-procedural RFR and dPR pullbacks yields similar results to iFR. Compared with an angiography-guided strategy, a pullback-guided PCI strategy with any of the 3 NHPRs reduced the number and the total length of treated lesions. (Study to Examine Correlation Between Predictive Value and Post PCI Value of iFR, RFR and dPR; UMIN000033534)., Competing Interests: Author Relationship With Industry Dr. Escaned has provided consulting and speaking services at educational events for Abbott, Boston Scientific, and Philips Healthcare. Dr. Mizukami has received consulting fees from HeartFlow. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2020. Published by Elsevier Inc.)

Objectives: The aim of this study was to compare clinical outcomes of different bifurcation percutaneous coronary intervention (PCI) techniques., Background: Despite several randomized trials, the optimal PCI technique for bifurcation lesions remains a matter of debate. Provisional stenting has been recommended as the default technique for most bifurcation lesions. Emerging data support double-kissing crush (DK-crush) as a 2-stent technique., Methods: PubMed and Scopus were searched for randomized controlled trials comparing PCI bifurcation techniques for coronary bifurcation lesions. Outcomes of interest were major adverse cardiovascular events (MACE). Secondary outcomes of interest were cardiac death, myocardial infarction, target vessel or lesion revascularization, and stent thrombosis. Summary odds ratios (ORs) were estimated using Bayesian network meta-analysis., Results: Twenty-one randomized controlled trials including 5,711 patients treated using 5 bifurcation PCI techniques were included. Investigated techniques were provisional stenting, T stenting/T and protrusion, crush, culotte, and DK-crush. Median follow-up duration was 12 months (interquartile range: 9 to 36 months). When all techniques were considered, patients treated using the DK-crush technique had less occurrence of MACE (OR: 0.39; 95% credible interval: 0.26 to 0.55) compared with those treated using provisional stenting, driven by a reduction in target lesion revascularization (OR: 0.36; 95% credible interval: 0.22 to 0.57). No differences were found in cardiac death, myocardial infarction, or stent thrombosis among analyzed PCI techniques. No differences in MACE were observed among provisional stenting, culotte, T stenting/T and protrusion, and crush. In non-left main bifurcations, DK-crush reduced MACE (OR: 0.42; 95% credible interval: 0.24 to 0.66)., Conclusions: In this network meta-analysis, DK-crush was associated with fewer MACE, driven by lower rates of repeat revascularization, whereas no significant differences among techniques were observed for cardiac death, myocardial infarction, and stent thrombosis. A clinical benefit of 2-stent techniques was observed over provisional stenting in bifurcation with side branch lesion length ≥10 mm., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)