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Background: Angina without angiographic evidence of obstructive coronary artery disease (ANOCA) is a highly prevalent condition with insufficient pathophysiological knowledge and lack of evidence-based medical therapies. This affects ANOCA patients prognosis, their healthcare utilization and quality of life. In current guidelines, performing a coronary function test (CFT) is recommended to identify a specific vasomotor dysfunction endotype. The NetherLands registry of invasive Coronary vasomotor Function testing (NL-CFT) has been designed to collect data on ANOCA patients undergoing CFT in the Netherlands., Methods: The NL-CFT is a web-based, prospective, observational registry including all consecutive ANOCA patients undergoing clinically indicated CFT in participating centers throughout the Netherlands. Data on medical history, procedural data and (patient reported) outcomes are gathered. The implementation of a common CFT protocol in all participating hospitals promotes an equal diagnostic strategy and ensures representation of the entire ANOCA population. A CFT is performed after ruling out obstructive coronary artery disease. It comprises of both acetylcholine vasoreactivity testing as well as bolus thermodilution assessment of microvascular function. Optionally, continuous thermodilution or Doppler flow measurements can be performed. Participating centers can perform research using own data, or pooled data will be made available upon specific request via a secure digital research environment, after approval of a steering committee., Conclusion: NL-CFT will be an important registry by enabling both observational and registry based (randomized) clinical trials in ANOCA patients undergoing CFT., Competing Interests: Declaration of Competing Interest NL-CFT is supported by research grants from Dutch Cardiovascular Alliance consortium IMPRESS (2020B004), Philips and Abbott. Damman P received research grants, lecture and consultancy fees from Phillips, and research grants and lecture fees from Abbott Vascular. Van Royen N has received research grants from Philips, Biotronik, Medtronic and Abbott and speaker fees from Microport, Rainmed and Abbott. Van ‘t Hof A received research grants and lecture fees from Abbott Vascular, Medtronic, Boehringer Ingelheim, Astra Zeneca and AMGEN not related to this work. Van de Hoef T received institutional research grants and consultancy fees from Philips and Abbott Vascular. Appelman Y received research grant from Dutch Heart Foundation IMPRESS, lecture and consultancy fees from Abbott Vascular and Phillips. Woudstra P received lecture fees from Philips. All other authors have no disclosures., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Coronary microvascular dysfunction is a highly prevalent condition of both structural and functional coronary disorders in patients with angina and nonobstructive coronary artery disease (ANOCA). Current diagnostic modalities to assess microvascular function are related to prognosis, but these modalities have several technical shortcomings and lack the opportunity to determine true coronary blood flow and microvascular resistance. Intracoronary continuous thermodilution assessment of absolute coronary flow (Q) and microvascular resistance (R) was recently shown to be safe and feasible in ANOCA. Further exploration and implementation could lead to a better understanding and treatment of patients with ANOCA. This review discuss the coronary pathophysiology of microvascular dysfunction, provides an overview of noninvasive and invasive diagnostics, and focuses on the novel continuous thermodilution method. Finally, how these measurements of absolute Q and R could be integrated and how this would affect future clinical care are discussed., Competing Interests: Funding Support and Author Disclosures Drs Jansen, Konst, Elias-Smale, van Royen, and Damman, have received a research grant from Abbott. Dr Damman has received consultancy fees and research grants from Philips. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Results: In 100 patients (mean age 67.1, 65% male), no significant differences were observed in ACT values obtained from the guiding catheter and arterial sheath (mean difference (MD) -18.3 s; standard deviation (SD) 96 s; P =0.067). Contrarily, ACT values obtained from the intravenous line were significantly lower as compared to values obtained from the guiding catheter (MD 25.7 s; SD 75.5; P =0.003) and arterial sheath (MD 39 s; SD 102.8; P < 0.001). Furthermore, ACT measurements from the arterial sheath showed a statistically significant proportional bias when compared to the other sampling sites (sheath vs. catheter, r  = 0.761, P =0.001; sheath vs. IVL, r  = 1.013, P < 0.001)., Conclusions: The present study shows statistical significance and possibly clinically relevant variations between ACT measurements from different sample sites. Bias in ACT measurements may be minimized by using uniform protocols for ACT measurement during cardiac catheterization., Competing Interests: The authors have no conflicts of interest to declare., (Copyright © 2021 J. C Heemelaar et al.)

Background: It is already known that high coronary microvascular resistance (Rμ) is linked to altered left ventricular stiffness and might be an early indicator of heart failure with preserved ejection fraction (HFpEF). Left atrial dysfunction, on the other hand, varies according to the grade of left ventricular diastolic dysfunction. This is the first study to use the latest development for invasive assessment of Rμ and to combine it with echocardiographic assessment of left atrial strain during reservoir phase (LAS r ) by speckle tracking in relation to left ventricular (LV) diastolic function., Methods and Results: An invasive angiogram was performed in 97 patients because of suspected ANOCA. All patients underwent comprehensive echocardiography, yet image quality was poor in 15 patients leaving 82 patients to include in the final analysis. In order to compare Rμ with LAS r values, patients were divided into 4 groups based upon normal values of Rμ as defined by Fournier et al. The mean LAS r was plotted against the four resistance groups. The LAS r was 48.6% in the lowest resistance group, and 40.1%, 36.3% and 30.1% in the low intermediate, high intermediate and high resistance group respectively. These differences were significant compared to the lowest resistance group (p < 0.05). Although higher Rμ groups showed more diastolic dysfunction, LAS r was already decreased irrespective of the severity of diastolic dysfunction., Conclusion: This study shows a relationship between increased Rμ and reduced LAS r , that seems to precede conventional measures of left ventricular diastolic dysfunction. This suggests that microvascular dysfunction might be an early indicator for the development of impaired LA function., Competing Interests: Declaration of Competing Interest Nico Pijls has Institutional grant; Abbott, Hexacath. Consultant; Abbott, Opsens, General Electric. Minor equities Philips, GE, ASML, Heartflow. All others have nothing to declare., (Copyright © 2021 Elsevier B.V. All rights reserved.)