A systematic review of enrolment criteria and treatment efficacy for microvascular angina.

Background: Microvascular angina (MVA) is an important contributor to morbidity and mortality in patients with non-obstructive coronary artery disease. Despite improvements in its recognition and diagnosis, uncertainty remains around the most effective treatment strategy, and more data are needed.

Aims: We aimed to evaluate the quality of patient selection in treatment studies of MVA and provide a contemporary overview of the evidence base for the treatment of MVA.

Methods: PubMed, the Cochrane Library and Google Scholar were searched from inception to 4 November 2023 for all treatment studies in patients with angina and non-obstructive coronary artery disease or coronary microvascular dysfunction. Populations with acute coronary syndrome were excluded (PROSPERO: CRD42023383075).

Results: Forty-three studies were included. By contemporary definitions of MVA according to the Coronary Vasomotor Disorders International Study Group criteria, 11 (26%) studies enrolled patients with "definitive" MVA, 24 (56%) with "suspected" MVA, and 8 (19%) did not enrol patients who met the diagnostic criteria. A total of 24 unique treatment interventions were investigated. Most studies were observational and single armed (12/24, 50%) or had a single randomised study (9/24, 38%). Ranolazine is the most well-studied intervention drug. Double-blind randomised controlled trials of ranolazine (n=6) have shown inconsistent improvements in Seattle Angina Questionnaire scores and coronary flow reserve with short-term follow-up.

Conclusions: Treatment studies of MVA enrolled a heterogeneous population, with only a quarter meeting contemporary diagnostic criteria for definitive MVA. There is a paucity of high quality, randomised data to support any specific treatment intervention. Larger studies with robust selection criteria, blinded patient-reported outcomes, and long-term follow-up are needed.