Perceval Sutureless Pericardial Bioprosthesis valve: Clinico-pathological and Experimental Observations Bioprotesi pericardiche sutureless perceval: aspetti clinico-patologici ed osservazioni sperimentali

Background Excellent performances have been demonstrated in haemodynamic outcomes, safety, and versatility of use in the sutureless Perceval aortic valve (LivaNova, London, UK). However, several questions remain unanswered, especially regarding the effects of the “collapsing” during the reduction of the dimensions of the bioprostheses before implantation, and long-term durability: the design of this prosthesis closely resembles that of the Freedom Solo stentless prosthesis that was associated with a significant incidence of Structural Valve Deterioration (SVD) in different studies. Our research focused on understanding the impact of the “collapsing” in the pericardial structure and the modality of failure of this bioprosthesis when implanted in humans. Materials and methods To analyse the collapsing impact, 12 collapsed at 15 min (surgical procedure collapsing time), 60 and 180 min duration, and 4 uncollapsed (controls) LivaNova Perceval S prostheses were morphologically studied. Gross, histology and scanning electron microscopy (SEM) analysis were performed. Multiple sections of pericardial cusps have been stained with Hematoxylin-Eosin (HE), Azan Mallory, Elastic Van Gieson and Picrosirius Red, where a morphometrical analyses was performed by measuring the length of the collagen period. SVD was investigated in 33 Perceval bioprosthesis explanted in different European centres, from July 2007 to January 2017, participating to PIVOT TRIAL V10601, PIVOTAL TRAIL V10801, and CAVALIER TRIAL TPS001. In all the explants gross, histology (HE, Azan Mallory, Elastic van Gieson, Von Kossa, Gram stains), were performed. To assess a potential reduction of the effective orifice area (EOA) due to fibrous tissue overgrowth, the ratio expressed in percentage between the EOA area and the total area of the bioprosthesis on ventricular side was measured. Results Gross examination after collapsing and deployment revealed optimal cusp cooptation and absence of tears, perforation or folding. Moreover, prosthetic frame showed a preserved shape without distortion. Histology and SEM exhibited neither breaks nor differences in waviness periodicity of the fibrosa collagen fibers when compared to controls. Collagen wavelength periodicity measurement data did not reveal any statistically significant differences among the study groups (15 min collapse: 16.55±2.89 µm; 60 min collapse: 17.01±3.11 µm; 180 min collapse: 16.45±2.13 µm) and the un-collapsed controls (16.51±2.65 µm) and with unmounted pericardium (17.47±2.50 µm) (P=NS). Thirtythree bioprosthesis implanted in humans were examined. Endocarditis was diagnosed in 36% of all, which was similar to that reported for bioprosthesis valves, SVD by dystrophic calcification in 12% (only 4 cases), fibrous pannus overgrowth in 12% and paravalvular leak in 12%. Fibrous tissue overgrowth (on the valve and on the stent) was 61%, with and incidence of almost 83% in the bioprostheses with time in place more than one month. This alteration involved the valve as main pathology, causing mainly orifice stenosis, or was associated to other failure modalities, as endocarditis, calcific dystrophy, or paravalvular leak. Its distribution was in the valve, in valve and nitinol stent or climbing the sole stent, occluding sometimes the spaces of nitinol network. Conclusions Pre-implantation collapse and ballooning procedures do not affect the structural integrity of the collagen fibers of the pericardial cusp tissue of Perceval S sutureless valve bioprosthesis. In 4 cases early SVD by dystrophic calcification occurred at time in place of 5-6 years, questioning the efficacy of the anticalcification treatment of the pericardium. Progressive fibrous tissue overgrowth, invading the valve orifice, was the cause of the bioprosthesis stenosis even in absence of calcific dystrophy and did not spare the stent and nitinol network. Despite the evolution on new technologies, design and pericardial treatment, the fibrous tissue overgrowth remains a major concern of this new generation bioprostheses.