Pediatric cardiac surgery: how to equip a program with implantable medical devices in the current era

Pediatric cardiac surgery (PCS) is one of the most specialized domains in the cardiovascular field and has benefited from numerous biotechnological innovations since its emergence in the 1950’s. Most PCS programs were founded decades ago, but our experience shows there is still a need for the creation of new programs in selected areas, even in Western countries. A PCS program was not present at our institution until October 2020, despite being the leading university hospital in a region of 6 million inhabitants.

Founding the PCS program was an exciting and incredibly challenging task, the priority being to build a dedicated multidisciplinary team of specialists working towards the same goal. The technical aspect, ensuring availability of the right precision equipment such as cardiopulmonary bypass machines, surgical instruments and implantable medical devices, was also crucial to the success of the program.

Specificities of the discipline include the need for multiple reoperations in some children born with congenital heart diseases (e.g. single ventricles and tetralogy of Fallot). Furthermore, reoperations are almost systematic after the implantation of prosthetic valves as a result of patient growth. PCS is also characterized by a broad variety of practice and the persistent lack of strong evidence in favor of one device versus another in a determined category. Therefore, the choice of implantable medical device remains at the discretion of the surgeon.

Alongside the usual set of sutures, clips, cannulas and drains, a PCS unit needs to be equipped with specific implantable devices:

Patches:

These devices are widely used given the frequency of conditions such as ventricular septal defect and tetralogy of Fallot, and the subsequent need for intracardiac defect closure. Bovine pericardium, treated with glutaraldehyde (e.g. Edwards bovine pericardial patch, Edwards Lifesciences) or not (e.g. PhotoFix®, CryoLife), represents a popular material. Alternatives consist of synthetic devices which include expanded polytetrafluoroethylene (e.g. Gore® Acuseal, W.L. Gore & Associates) and knitted polyester (e.g. Hemapatch, Getinge). Polytetrafluoroethylene felts (e.g. Bard® PTFE, Becton Dickinson) are used as pledgets to reinforce suture lines when necessary. Last but not least, the use of autologous pericardium is one way to reduce the consumption of heterologous patches. Of note, the above mentioned patches are also employed to enlarge pulmonary arteries and/or reconstruct the pericardium.

Vascular Prostheses:

Given the variety of indications and the wide size range of children, being supplied with an extended range of vascular conduits is mandatory. Polytetrafluoroethylene conduits (e.g. by W.L. Gore & Associates) range from 3 to 5 mm for systemic-to-pulmonary artery shunts, from 5 to 14 mm for pulmonary artery branch replacement and from 16 to 20 mm for the extracardiac Fontan procedure. In addition, polyester prostheses ranging from 24 to 30 mm (e.g. Cardioroot, Getinge or Gelweave™ Valsalva, Terumo Aortic) can be used for Ross procedures in adolescents to prevent dilatation of the pulmonary autograft.

Bioprosthetic Valved Conduits:

Very few models of pediatric bioprosthetic valves are commercialized. Reconstruction of the right ventricular outflow tract (e.g. in truncus arteriosus repair) represents their essential use. The most implanted conduits are the Contegra® conduit (bovine jugular vein, 12 to 22 mm) and the Hancock® conduit (porcine aortic valve, 12 to 25 mm). Both models (manufactured by Medtronic) have limited durability and surgical or transcatheter replacement is required in the midterm following implantation. The Hancock® conduit, however, is reinforced with a non-stretchable external ring, preventing future insertion of an oversized transcatheter prosthetic valve. The Freestyle® bioprosthesis (Medtronic) (porcine aortic root, 19 to 29 mm) is used in larger patients in times of pulmonary or aortic homograft shortage.

Mechanical Valves:

Mechanical prostheses are implanted considerably less frequently in children compared to bioprosthetic valves. Nevertheless, such prostheses are necessary because of rare but inevitable indications. Mitral valve replacement with a mechanical prosthesis represents the very last solution following failed attempts to repair the valve. The aortic valve is affected to a lesser extent (when the Ross procedure cannot be performed). Given the rarity of implantation, supply of mechanical valves should be shared with an adjacent adult cardiac surgery program. The smallest available valve is labelled with a diameter of 15 mm (SJM™ Masters HP, Abbott), which allows for use in young toddlers.

Annuloplasty Rings:

Likewise, this type of devices is very rarely implanted in children, which explains why mitral and tricuspid annuloplasty rings of pediatric diameters are not commercialized. Consequently, common storage with an adjacent adult cardiac surgery program is again suggested, in the eventuality of implantation in teenagers.

The range of cardiovascular implantable devices in the pediatric cardiac surgeon’s cupboard is wide. Knowledge on properties, advantages and drawbacks of each type of implantable device is seen as good practice and should be part of surgical training. Selection of devices should be made according to evidence, ease of use and cost. In our program, we 1/ use autologous pericardium whenever possible and appropriate, 2/ favor the implantation of polytetrafluoroethylene patches over animal-derived patches where necessary, 3/ have shortlisted and share the stock of aortic polyester prostheses, mechanical valves and annuloplasty rings with the adult cardiac surgery unit.