Surgical procedures for correction of congenital cardiac diseases are often accomplished with use of patch material. Autologous pericardium is not usually sufficient especially in reoperations or staged procedures. A diverse range of patches including synthetic or xenogeneic are available as tissue substitutes. Ideal patch should be readily available, easy to handle, has growth potential, can recellularize, remodel, resist infection and coapt well to suture lines for proper hemostasis and lower thrombogenicity [2, 3]. Unfortunately, none of the available patches meet all of these criteria. Synthetic patches e.g. Dacron and Gore-Tex cannot remodel, regenerate, nor grow. They are liable to infection stiffening and calcification over time after implantation [4]. Bioprosthetic patches show better surgical handling and more resistance to infection than synthetic patches. Processing of xenopericardium (decellularization) is important to remove cellular antigens and procalcific materials while maintaining integrity of extracellular matrix. In addition, cross linking (by agents e.g. glutaraldehyde) increases stability and strength of tissue and keeps it non-antigenic [5, 6]. However, late calcification is not uncommon and may be related to the type of processing and decellularization as well as the anticalcific treatment.
Tissue engineering is adopted to avoid some of these drawbacks. The bovine pericardial patch (CardioCel) is treated to remove antigens and calcium binding phospholipid sites, thus limiting calcification and reducing reoperation [7]. Dye-mediated photo oxidation is an alternative to glutaraldehyde for cross linking of collagen fibers in bovine pericardium (Photofix) [8].
Limitations related to availability and costs of these types are considered in our choice. We are still using autologous and bovine pericardia for repair. Equine pericardium has been introduced at our center for the last 3 years. EP is a decellularized patch not fixed with glutaraldehyde. Subjectively we found it softer, more pliable, and easier for handling especially in areas requiring a complex patch shape. It shows excellent adaptation to tissues notably in reconstruction of the aorta in neonates with HLHS or other complex arch pathology.
An interesting animal study by Dohmen et al. showed favorable characteristics of EP. Decellularized equine pericardia were implanted into the descending aorta of juvenile sheep. Explanation was done after 4 months. There was no evidence of thrombosis, infection, calcification, or degeneration. Extracellular matrix was preserved. A monolayer of endothelial cells was noticed on the inner side of the patch and neovascularization was found in the outer side. This study showed remodeling and regeneration of equine pericardium [9].
EP is successfully used in varying surgical sites. EP is also used as dural substitute. It is transparent, impermeable to CSF, does not adhere to cortex and facilitates regeneration of dura. It has the advantages of greater physical resistance and less liability to infection than bovine pericardium [10]. EP was also used in myringoplasty (to close tympanic membrane perforation). Long-term closure rate was better in EP group compared to BP (bovine pericardium). EP is thinner, easier to handle and remodel in proper shape than BP [11]. EP is used in treatment of chronic wounds and ulcers of diabetic foot. It provides temporary biological cover scaffold that promote healing [12]. Few data are found in literature regarding use of equine pericardium in cardiovascular surgery. EP was approved for pediatric cardiac reconstructive surgery and was successfully used as a substitute to arterial homograft to replace infected aortic aneurysm [13, 14]. Equine pericardial patch is used to close the pericardial sac to decrease risk of repeat sternotomy. Lesser adhesions were found in equine pericardial patched group when compared with pericardium left open group [15]. On the contrary others reported intense epicardial reactions, degeneration, and calcification. This discouraged most surgeons from using xenopericardium for closure of pericardial sac [16]. We do not routinely close the pericardium in pediatric patients. We think that glutaraldehyde added to fix pericardial patch might account for these undesirable changes. Accordingly, glutaraldehyde-free Matrix patch ay be a better alternative. An experimental study was conducted by Rassoli et al. compared equine, bovine, and porcine pericardia mechanically and histologically. Equine pericardium showed less stiffness under biaxial tension and hence it is more appropriate for manufacturing bioprosthetic valves as recommended by authors [17]. EP was used to construct a stentless bioprosthetic valve with good hemodynamic results comparable to Toronto SPV valve as shown in an animal study by Muller and Segsser [18]. We used EP for augmentation of valve repair in 9 cases with good results in terms of coaptation and competence. We prefer to do bicuspidization of pulmonary valves with EP. Early follow up results of our series showed favorable outcomes of EP comparable to BP with respect to survival and freedom from reoperations. A few clinical trials compared the use of EP and BP in surgery for congenital cardiac diseases. Vitanova et al. reported higher rate of recoarctation after Norwood stage 1 for HLHS when equine pericardium was used for reconstruction of aortic arch in comparison to homograft, autologous pericardium, and bovine pericardium. They concluded that equine pericardium was the only risk factor for recoarctation and cannot be recommended for repair of HLHS [19]. We operated 7 patients in our series with HLHS using EP. Transcatheter dilatation was needed for one patient and responded well to dilatation. The remaining patients had excellent arch reconstruction using EP and many have undergone second and final stage surgery without evidence of significant calcification or stenosis.
The cost of different materials varies in different countries. However, in Saudi Arabia the coast of the EP is comparable to BP (EP cost is 900 dollars and BP cost is 825 dollars). We agree with Veličković et al. [20] that the rate of revision or reoperation related to patch failure should be considered when economic aspect is evaluated.
This study is a retrospective single center study including a relatively small number of patients with different congenital cardiac diseases. Prospective studies with larger sample size and longer follow up period are needed to evaluate long term outcome.
