Measuring Absolute Coronary Flow and Microvascular Resistance by Thermodilution: JACC Review Topic of the Week.

Diagnosing coronary microvascular dysfunction remains challenging, primarily due to the lack of direct measurements of absolute coronary blood flow (Q) and microvascular resistance (R _μ ). However, there has been recent progress with the development and validation of continuous intracoronary thermodilution, which offers a simplified and validated approach for clinical use. This technique enables direct quantification of Q and R _μ , leading to precise and accurate evaluation of the coronary microcirculation. To ensure consistent and reliable results, it is crucial to follow a standardized protocol when performing continuous intracoronary thermodilution measurements. This document aims to summarize the principles of thermodilution-derived absolute coronary flow measurements and propose a standardized method for conducting these assessments. The proposed standardization serves as a guide to ensure the best practice of the method, enhancing the clinical assessment of the coronary microcirculation.
Competing Interests: Funding Support and Author Disclosures Drs Belmonte, Bertolone, and Viscusi are supported by a research grant from the CardioPaTh PhD Program. Dr Pijls has received institutional research grants from Abbott; has consulting relationships with and receives fees from Abbott and Coroventis; has equity in ASML, General Electric, HeartFlow, and Philips; is a member of the Scientific Advisory Board of Heartflow; and has patents pending in the field of the coronary microcirculation and aortic valve stenosis. Dr Mizukami has received consulting fees from Zeon Medical and HeartFlow; and has received speaker fees from Abbott Vascular. Dr Barbato has received speaker fees from Abbott Vascular, Boston Scientific, and GE. Dr Dannab has received grants from Philips, Abbott, and AstraZeneca; and has received consulting fees from Philips. Dr Keeble has received honoraria and institutional research funding from Abbott Vascular, Medtronic, Terumo, Zoll, and Shockwave; has received consulting fees from BD; has received speaker fees from Cardionovum, Abbott Vascular, and AstraZeneca; is on the steering group for the ORBITA-2 trial; and is on the committee for the National Institute for Health and Care Research Invention for Innovation (i4i), British Cardiovascular Intervention Society and Resuscitation Council. Dr Kern is a speaker for Abbott Vascular, Boston Scientific, Acist, Opsens, and Zoll. Dr Fearon has received institutional research support from Abbott, Boston Scientific, and Medtronic; has a consulting relationship with CathWorks and Siemens; and has stock options with HeartFlow. Dr Collet has received research grants from Biosensors, HeartFlow, and Abbott Vascular; and has received consultancy fees from HeartFlow, Abbott Vascular, Boston Scientific, Opsens, and Philips Volcano. Dr De Bruyne has consulting relationships with Boston Scientific, Abbott Vascular, CathWorks, Siemens, and Coroventis Research; has received research grants from Abbott Vascular, Coroventis Research, Cathworks, and Boston Scientific; and holds minor equities in Philips Volcano, Siemens, GE Healthcare, Edwards Lifesciences, HeartFlow, Opsens, Sanofi, and Celiad. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
(Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)