Design and rationale for MICROFIT (Microvascular Coronary Rehabilitation For Improving Treatment)-a feasibility randomized trial of intensive lifestyle rehabilitation for symptomatic coronary microvascular dysfunction.

BACKGROUND: Coronary microvascular dysfunction (CMD), a common endotype of angina with non-obstructed coronary arteries (ANOCA), is linked to poor cardiovascular outcomes, and can significantly impact quality of life, mental health, and functional capacity. CMD management strategies focus on symptom control with antianginal therapies, with limited effect and prognostic benefit. While lifestyle changes and risk factor modification are advocated by international guidelines, evidence supporting cardiac rehabilitation for CMD is sparse. It is proposed that MICROFIT-a personalized lifestyle intervention programme, utilizing exercise training and dietary counselling, underpinned by behavioural change techniques, can improve symptoms of angina in patients with CMD. This study aims to examine the feasibility of undertaking a multicenter randomized controlled trial (RCT) of the MICROFIT programme vs. usual care in patients with CMD and explore its effects on symptoms of angina. DESIGN AND METHODS: Forty participants (aged >18) will be recruited from two centers and randomized 1:1 to receive either MICROFIT intervention plus usual care or usual care only. The primary outcome is feasibility, measured by recruitment and retention, and adherence to the intervention. Participants' and practitioners' experience of the programme will be explored qualitatively. The secondary outcome is change in angina symptoms, to inform the design and power calculations for a future RCT. Other exploratory outcomes include changes to functional capacity (VO2 peak), cardiovascular MRI-derived markers of myocardial perfusion and coronary vascular function, and biomarkers of metabolic syndrome. A sub-study will explore experiences of the ANOCA diagnostic pathway from patient and healthcare professionals' perspective. ETHICS AND DISSEMINATION: Ethics approval was granted by the NHS Health Research Authority Plymouth and Cornwall Research Ethics Committee (reference: 24/SW/0125, 30th October 2024). Study findings will be disseminated via presentations to relevant stakeholders, national and international conferences and open-access peer-reviewed research publications.Clinical Trial Registration: NCT06681896.