Background Thrombocytopaenia in the post-operative period in the Perceval Sutureless valve is a well-documented phenomenon. Whilst no significant adverse short-term effects have been recorded, its effects on mid-term valve function are unknown. This study aimed to assess the long-term haemodynamic impacts of thrombocytopaenia on the Perceval Valve. Methods This was a case-control matched retrospective cohort study of all patients who had undergone Perceval Valve implantation in an Australian centre between 2014-2023. Primary endpoints were structural valve degeneration (SVD) at last recorded follow up, mean valve gradient (MVG) and peak valve gradient (PVG). Patients with thrombocytopaenia were compared with to those without thrombocytopaenia. Results 200 patients underwent Perceval Valve implantation in the recorded timeframe, with post-operative platelet data available in 193 patients. 148 (77%) patients experienced post-operative thrombocytopaenia (P<0.001). Mean follow up was 31 months. Pre-operative platelet counts were significantly lower in the thrombocytopaenia group (208.9 vs 278.3 P=<0.001). Other baseline demographics were non-statistically different. SVD was significantly higher in those with thrombocytopaenia compared to those without (6.2% vs 0 p=0.05), although this did not reach significance in the case control cohorts. 5-year freedom from SVD was 68% in those with thrombocytopaenia. MVG at 6 (13.2mmhg vs 11.94mmHg p=0.43), 24 (15.45mmHg versus 11.6mmHg p= 0.24) and 30 (17.2mmHg vs 8mmHg p=0.31) months were higher in the thrombocytopaenia group, although not statistically significant. Conclusion Perceval valve implantation and thrombocytopaenia may be associated with SVD and higher mean valve gradients at mid-term follow up. Larger studies are required to confirm these findings.