Improvement of invasive microvascular indices following guideline-directed treatment of structural coronary microvascular dysfunction: a case report.

Background: Structural coronary microvascular dysfunction (CMD) is a major pathophysiological mechanism underlying ischaemia with non-obstructive coronary arteries and is associated with persistent angina and impaired functional capacity. Although contemporary European guidelines recommend a structured, stepwise pharmacological approach, invasive confirmation of physiological improvement following this specific treatment protocol remains limited. Case summary: An 82-year-old woman presented with typical angina and stress-induced ischaemia on myocardial scintigraphy. Coronary angiography demonstrated a proximal left anterior descending artery stenosis <50% with a fractional flow reserve (FFR) of 0.90. Continuous thermodilution performed in the left anterior descending artery revealed reduced coronary flow reserve (CFR 2.2) and elevated minimal microvascular resistance (798 WU), consistent with structural CMD.A structured, symptom-guided pharmacological optimization strategy was initiated, including statin therapy, angiotensin-converting enzyme inhibition, beta-blockade, calcium-channel blockade, and ranolazine.At 4-month follow-up, angina was markedly improved. Repeat invasive assessment in the same coronary territory demonstrated improvement of microvascular indices (CFR 3.8; minimal microvascular resistance 461 WU). Discussion: This case illustrates that guideline-directed medical therapy for coronary microvascular dysfunction may be associated with both symptomatic improvement and objective changes in microvascular function.