Abstract 4138477: Small Vessels, Big Challenges: Clinical and Demographic Correlates of Failure to Respond to Optimal Medical Therapy in Patients with Microvascular Angina

Background: Microvascular angina (MVA), resulting from coronary microvascular dysfunction, affects 40-50% of patients with exertional chest pain or dyspnea and a normal coronary angiogram. This condition significantly impairs quality of life and elevates the risk of major cardiac events, including myocardial infarction, stroke and death. MVA is classified as 'structural' (coronary flow reserve [CFR] <2.5&index of microcirculatory resistance [IMR] >25) or 'functional' (CFR <2.5&IMR <25). Current treatments are empirical, necessitating further investigation. Methods: This single-centre, retrospective study conducted in South Wales from 2019-24 examined MVA cases confirmed via national electronic health records. The Canadian Cardiovascular Society (CCS) angina grade was assessed at diagnosis and post optimal medical therapy (OMT) during clinic visits. Ordinal logistic regression was used to identify independent correlates of higher CCS grade, considering baseline LDL, age, diffuse epicardial disease, sex, hypertension, kidney function, smoking status and HbA1c levels as covariates. Results: Among 64 identified MVA cases (median age 69 yrs, IQR 61.3-77.8; 68.8% male), 81.3% had structural MVA, 6.3% functional MVA and 12.5% mixed disease. Coronary vessel testing was performed on 1, 2 or 3 vessels in 29.7% (n=19), 53.1% (n=34; 21 positive [+ve] in 2 vessels, 13 +ve in 1 vessel) and 17.2% (n=11; 5 +ve in 3 vessels, 5 +ve in 2 vessels, 1 +ve in 1 vessel) of cases, respectively. The LAD was most commonly affected vessel (82.8%). At diagnosis, 79.7% had CCS grade III or higher (Fig 1). Post OMT, 45.3% achieved CCS grade 0-I, 31.8% CCS grade II and 15.6% remained at CCS grade III (refractory angina). Medications included ranolazine (84.4%), beta-blockers (70.3%) and calcium channel blockers (28.1%). Ordinal logistic regression analysis (X 2 =0.27, p=0.033) identified baseline LDL (95% CI [0.16, 1.26]; p=0.011), age (95% CI [-0.12, -0.001]; p=0.045), diffuse epicardial disease (95% CI [0.016, 2.13]; p=0.047) and male sex (95% CI [0.066, 2.36]; p=0.038) as independent correlates of higher CCS grade, signifying poor response to OMT. Conclusion: MVA manifests regionally, underscoring the need for multi-territory testing. Although tailored OMT proved effective for many, 15.6% of patients continued to experience refractory symptoms (CCS grade III). This highlights the necessity for alternative therapeutic strategies to improve patient outcomes in this challenging condition.