Pericardium in Reconstructive Urologic Surgeries: A Systematic Review and Meta-Analysis

INTRODUCTION

The use of pericardium has been expanded into different surgical modalities; however, there are scarce data regarding the feasibility of the pericardium in reconstructive urologic surgeries. We systematically reviewed the literature on the effectiveness of the pericardial tissue for reconstructive urologic surgeries.

MATERIALS AND METHODS

PubMed and Scopus were searched online for evidence on the use of the pericardium in urologic surgeries. Through the methodology recommended by the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines, 38 of 4,071 studies were identified.

RESULTS

A total of 715 patients and 139 animals underwent reconstructive urologic surgeries using the pericardium. Bladder, urethral, and renal reconstructions were successful in 100% of the human cases. The rates of dissatisfaction, glans hypoesthesia, and penile shortening were comparable between the pericardial graft surgeries and the other operations during penile straightening, but there was a trend among the patients with pericardial grafts toward having a more penile curvature at follow-up (risk ratio [RR] 2.03, 95% CI 0.90-4.61, p = 0.09; I2 = 0%). Among the animal studies, there were 4 reports of penile reconstruction, 7 studies of bladder reconstruction, and 1 study of urethroplasty. Bladder reconstruction and urethroplasty were successful in 83 and 20% of the animals, respectively. The pooled result of the stimulated intracorporeal pressure 5 V significantly favored pericardial grafts during penile reconstruction (RR 2.61, 95% CI 1.26-3.97, p = 0.0002; I2 = 0%).

CONCLUSIONS

Our systematic review demonstrates the feasibility of the pericardium, regardless of its type, in urologic surgeries. It, however, seems that urethral substitution needs further investigation. Given the lower cost, easier handling, and less immunogenicity of the pericardium, further studies are required to examine its pros and cons.

Impact of Clinically Relevant Elliptical Deformations on the Damage Patterns of Sagging and Stretched Leaflets in a Bioprosthetic Heart Valve

After implantation of a transcatheter bioprosthetic heart valve its original circular circumference may become distorted, which can lead to changes in leaflet coaptation and leaflets that are stretched or sagging. This may lead to early structural deterioration of the valve as seen in some explanted transcatheter heart valves. Our in vitro study evaluates the effect of leaflet deformations seen in elliptical configurations on the damage patterns of the leaflets, with circular valve deformation as the control. Bovine pericardial tissue heart valves were subjected to accelerated wear testing under both circular (N = 2) and elliptical (N = 4) configurations. The elliptical configurations were created by placing the valve inside custom-made elliptical holders, which caused the leaflets to sag or stretch. The hydrodynamic performance of the valves was monitored and high resolution images were acquired to evaluate leaflet damage patterns over time. In the elliptically deformed valves, sagging leaflets experienced more damage from wear compared to stretched leaflets; the undistorted leaflets of the circular valves experienced the least leaflet damage. Free-edge thinning and tearing were the primary modes of damage in the sagging leaflets. Belly region thinning was seen in the undistorted and stretched leaflets. Leaflet and fabric tears at the commissures were seen in all valve configurations. Free-edge tearing and commissure tears were the leading cause of valve hydrodynamic incompetence. Our study shows that mechanical wear affects heart valve pericardial leaflets differently based on whether they are undistorted, stretched, or sagging in a valve configuration. Sagging leaflets are more likely to be subjected to free-edge tear than stretched or undistorted leaflets. Reducing leaflet stress at the free edge of non-circular valve configurations should be an important factor to consider in the design and/or deployment of transcatheter bioprosthetic heart valves to improve their long-term performance.

Tissue processing techniques for fabrication of covered stents for small-diameter vascular intervention

Animal-derived pericardial tissue is a widely used biomaterial typically treated with glutaraldehyde (GA) to achieve immunological acceptance and long-term durability. However, GA fixation of biological tissue is associated with long-term failure due to degeneration and calcification. In this study, we evaluated two alternative tissue processing methods for the fabrication of pericardial tissue covered stents: detergent-based decellularization (decell) and limited exposure to GA (gentle-glut). Processed pericardial tissues were extensively characterized both in-vitro and in-vivo. Small-diameter covered stents were fabricated and the ability to seal perforation was evaluated in a flow circuit under physiological blood flow conditions. Results indicate that decell-treated tissue appeared with preserved architecture, tissue strength and stability. Gentle-glut tissue appeared with preserved architecture and increased tissue stability, compared to fresh, unprocessed tissue. Reduction of bioburden was demonstrated for both types of alternative treatments, as for GA fixation. Tensile testing demonstrated that both decell- and gentle-glut treated tissues respond better to low strain, as may occur during balloon inflation and stent deployment. Upon subcutaneous implantation in mice, gentle-glut and to a greater degree decell-treated tissue, elicit better host response, with evidence of active tissue remodeling and no detectable calcification, as compared with GA-treated tissue. Small-diameter stents covered with tissues from all groups successfully sealed perforation under physiological blood flow conditions in-vitro, without compromising flow. In summary, covered stents may perform better with pericardial tissue processed according to the methods described in this study. Adopting this methodology to other types of cardiovascular implants and tissues is also suggested.

STATEMENT OF SIGNIFICANCE

Pericardial tissue is a widely used biomaterial for cardiovascular implants, such as covered stents. The use of glutaraldehyde (GA) has become the method of choice for pericardial tissue fixation, making it immunologically acceptable in humans. However, GA-treated tissue is prone to several problems, such as degeneration and calcification that may lead to long-term failure. Here, we studied two alternative tissue processing techniques: fixative-free decellularization and limited exposure to GA. We've shown that both methods achieve better mechanical properties and promote better host acceptance, tissue remodeling and long-term durability. Since the availability of autologous tissue for transplantation is limited, these methods should be adopted for other types of cardiovascular devices, such as bioprosthetic valves, ultimately achieving better long-term results for patients.