The impact of coronary sinus reducer on the extent of ischaemia in functional stress tests

Background The coronary sinus Reducer (CSR) is a treatment option for patients with refractory angina due to obstructive coronary artery disease who are not candidates for further revascularization. Although symptomatic improvement is well established, its effect on objective measures of ischaemia is less well defined. Purpose To evaluate the effect of CSR implantation on objective measures of inducible ischaemia in patients with refractory angina, and to identify baseline predictors of clinical non-response. Methods We conducted a prospective cohort study of consecutive patients undergoing CSR implantation between 2011 and 2024. Patients underwent baseline assessment—including CCS angina class, six-minute walk test (6MWT), stress echocardiography (stress-Echo) and/or SPECT—and repeated evaluation six months post-procedure. The co-primary outcomes were the change in wall motion score index (WMSI) on stress-Echo and the change in the proportion of patients with moderate or severe ischaemia on SPECT. Clinical non-responders were defined as those without a ≥1-class improvement in CCS angina class at 12 months. Results Of 153 treated patients, 136 had complete stress-Echo or SPECT data. Median WMSI during stress improved from 1.38 to 1.23 (p < 0.001), and median LVEF at stress increased from 55% to 60% (p = 0.019). SPECT imaging showed a significant reduction in the proportion of patients with moderate or severe ischaemia from 55% to 25% (p < 0.001). Clinically, 88% of patients experienced an improvement of ≥1 CCS angina class at six months. Responders had higher baseline LVEF and lower WMSI than non-responders. Conclusions CSR implantation significantly reduced inducible ischaemia on functional stress testing in patients with refractory angina. Baseline myocardial function may help identify patients most likely to benefit from therapy.