Medical therapy efficiency on microvascular function in patients with non-obstructive coronary artery disease

Abstract Introduction Approximately one-third of all patients presenting with typical chest pain do not have obstructive (40%) epicardial coronary artery stenoses. Nevertheless, there is no unified treatment for those patients. Recently, the idea of optimal medical treatment only for patients with proven microvascular dysfunction was raised. Aim This study aims to evaluate the effect of optimal medical therapy on patients with typical angina chest pain without significant epicardial coronary artery narrowing (40% of lumen diameter) and with proven or unproven microvascular dysfunction. Methods In total, 34 patients with typical angina chest pain, diagnosed and treated at our hospital between 1 September 2024 and 1 December 2024, were prospectively included in the study. For all included patients, an invasive coronary artery angiography denying severe than mild coronary artery lesions (lumen stenosis 40%), accompanied by invasive microvascular testing (performing IMR and CFR), was performed. Regardless of the invasive test result for all patients, optimal medical treatment, including maximal tolerated doses of statin (low density lipoprotein cholesterol (LDL Ch) aiming 1,4 mmol/l), beta-blocker, calcium channel blocker, and metabolism-enhancing medication, was prescribed for at least 6 months. Then, symptoms were assessed using the Seattle Angina Questionnaire score. Patients who remained symptomatic (daily (0-30 points) or weekly (31-60 points)) were repeatedly referred for invasive angiography and invasive microvascular function assessment. Differences between the two groups were assessed using a paired-samples t-test in SPSS 28.0, with a significance level of p 0.05. Results Of all, 16 patients were diagnosed with microvascular dysfunction by invasive measurements. After 6 months of optimal medical therapy, 28 patients remained symptomatic; therefore, invasive measurements were repeated. Optimal medical therapy increased CFR values and decreased IMR in both groups (M = 0.11 (SD = 0.17); M = -1.00 (SD = 1.91); t(27) = 3.38, p = 0.002; and t(27) = -2.78, p = 0.01, accordingly). Deeper analysis revealed, that statistically significant positive effect of medical therapy was observed only in patients with diagnosed microvascular dysfunction: CFR (M=0.13(SD 0.19); t(15)=2.84, p = 0.013); IMR (M=-1.63 (SD 2.19); t(15)= -2,97, p = 0.09) over CFR (M=0.08(SD 0.14); t(11)=1.83, p = 0.095); IMR (M=-0.17 (SD 1.03); t(11)= -0.56, p = 0.586). Conclusions This study revealed the importance of instrumental microvascular dysfunction diagnostics and accurate indications for optimal medical therapy in settings of typical chest discomfort in the absence of epicardial coronary artery stenoses, as optimal medical therapy does not improve microvascular function in patients without pre-existing microvascular impairment.