Procedural factors influencing successful coronary sinus reducer implantation for refractory angina: A single-centre experience.

Background: Coronary sinus reducer (CSR) implantation is emerging as a novel effective percutaneous therapy for patients with refractory angina. Limited data exists examining the factors influencing successful CSR implantation. As CSR implantation becomes more widely adopted, a greater understanding of the procedural challenges which operators encounter is required.

Aim: To evaluate the patient and procedural characteristics influencing successful CSR implantation.

Methods: This was a retrospective cohort study of consecutive patients with refractory angina undergoing clinically indicated CSR implantation (February 2016 to August 2024) at a high-volume implanting centre in the UK. Patient and procedural characteristics affecting procedural difficulty were systematically analysed. Procedural difficulty was determined by 1) increasing total procedural time or 2) features of challenging equipment handling such as bellying, swan-necking or complete equipment fallout from the coronary sinus (CS).

Results: 102 out of 105 (97 %) patients underwent a successful CSR implant at the first attempt. Patients had a high rate of previous revascularisation (PCI: 85 %; CABG 64 %) and diabetes (58 %). Significant improvements in Canadian Cardiovascular Society (CCS) class were observed with 36 % of patients improving by ≥2 CCS classes and 71 % improving by ≥1 CCS class. A C- or non-C-shape of the CS was not associated with differences in procedural time (P = 0.52). However, the presence of both a valve and ridge in the CS was associated with significantly longer procedural times (P = 0.03). A ridge, alone or together with a valve, predicted features of procedural difficulty, such as bellying (ridge - OR: 2.69, P = 0.02; valve and ridge - OR: 4.58, P = 0.0006) and swan-necking (ridge - OR: 5.43, P = 0.001; valve and ridge - OR: 4.74, P = 0.002). Bellying, swan-necking, and complete fallout of equipment from the CS were associated with longer procedural times, but also with each other, suggesting their utility as indicators of procedural complexity.

Conclusion: In our experience, CSR implantation is safe and associated with high rates of procedural success. However, patient and procedural factors can influence the difficulty of CSR implantation. The presence of a ridge may make implantation more challenging. Bellying, swan-necking and complete equipment fallout may indicate increased procedural complexity. Greater awareness of these features will encourage operators to remain vigilant and adapt their implantation strategy when encountering challenging cases.