Rationale and design of European microcirculatory resistance and absolute flow team: The Euro-CRAFT registry.

INTRODUCTION: Coronary microvascular dysfunction (CMD) is increasingly recognized as an important cause of anginal symptoms and poor outcomes. Angina with nonobstructive coronary arteries (ANOCA) is often related to CMD. While physiological assessment of microcirculatory function by coronary bolus thermodilution is widely practiced, more precise and reproducible methodology as well as systematic assessment are necessary. Recently, absolute flow measurements by coronary continuous thermodilution and the concept of Microvascular Resistance Reserve (MRR) have been introduced.

AIM: The European microCirculatory Resistance and Absolute Flow Team (EuroCRAFT) registry aims to compare major adverse cardiac and cerebrovascular events (MACCE)-rates in patients with and without CMD based on MRR at 1-year follow-up.

METHODS: This prospective international, investigator-initiated, multicenter study is enrolling patients with stable chest pain suggestive of angina and nonobstructive epicardial coronary arteries on invasive coronary angiography, defined as fractional flow reserve >0.80. Patients will undergo coronary angiography and microvascular assessment using bolus and continuous thermodilution methods. The primary endpoint is to compare the rate of MACCE in patients with and without CMD assessed with MRR at 1 year. Based on the sample size estimation, 671 patients are initially planned for enrollment. We hypothesize that coronary continuous thermodilution-derived MRR has superior prognostic value for MACCE at 1 year compared to bolus thermodilution-derived microvascular metrics.

RESULTS: Study recruitment started in September 2022 and has been completed in May 2025, resulting in a total of 678 patients enrolled.