69 Invasive guidewire-based assessment of coronary microvascular function and vasoreactivity: a retrospective case series in a non-tertiary cardiology centre

Introduction Microvascular angina is a category of ischaemia with non-obstructive coronary arteries (INOCA) which typically occurs as exertional angina but may feature angina at rest if there is coexistent microvascular vasospasm. Coronary vasospasm typically produces anginal symptoms at rest with preserved exercise tolerance, often with a circadian pattern. The CorMicA trial demonstrated that stratified medical therapy guided by invasive guidewire-based measurements of microvascular resistance (IMR), coronary flow reserve (CFR), and fractional flow reserve (FFR), with acetylcholine vasoreactivity testing, improves angina and quality of life. This is a non-comparative summarised retrospective case series of patients undergoing invasive measurement of IMR, CFR, and FFR at a district general hospital in the United Kingdom over a seven-month period. Methods Using the electronic records of 16 patients who had undergone invasive assessment of microvascular resistance (with or without vasoreactivity testing), we assessed primary endpoints of whether the procedure changed management and whether there was a subsequent improvement in symptoms. Secondary endpoints included rates of positive tests for microvascular dysfunction (MVD) or vasospasm and significant adverse events. Results 5/16 (31%) patients who underwent invasive assessment of microvascular function were found to have clear-cut MVD with an IMR ≥ 25. A further 3 (20%) were felt to have mild, or borderline MVD. 9 of these 16 patients underwent acetylcholine testing, inducing vasospasm in 5/9 (56%). Two patients were found intra-procedurally to have obstructive coronary artery disease and underwent angioplasty. Excluding these, where available notes were sufficient to draw conclusions, 10/11 patients (91%) had a change in either diagnostic approach to or treatment of their symptoms following the procedure. 3/11 (27%; 2 with MVD, 1 with vasospasm) had a documented improvement in symptoms, although not all of these 11 had follow-up documentation. In terms of adverse events 1 patient with known chronic obstructive pulmonary disease developed significant bronchospasm during adenosine infusion. Two patients developed atrial fibrillation after acetylcholine infusion (with no known history of atrial fibrillation). Conclusion This retrospective observational case series suggests that invasive assessment of microvascular resistance and vasoreactivity in selected patients is feasible even in non-tertiary cardiology services equipped with cardiac catheterisation facilities, and that it is a high-yield investigation that frequently influences future investigative and therapeutic decisions. Conflict of Interest None