Surgical reconstruction of the right ventricular outflow tract—The clock is still ticking

The optimal device for heart valve replacement is yet to be developed. If this is certainly true for adult patients with acquired pathologies, the need for better materials is even more pressing in the setting of congenital heart disease, where any valve replacement activates a ticking clock towards the next procedure. In this issue of the Journal of Cardiac Surgery , Selcuk et al. 1 report their single ‐ center experience with the BioIntegral Biopulmonic Conduit ™ , implanted as a right ventricle ‐ to ‐ pulmonary artery conduit in 48 pediatric patients over a period of 13 months. 1 This is a stentless porcine heart valve covered with a 10 ‐ cm long porcine pericardial sleeve

The optimal device for heart valve replacement is yet to be developed. If this is certainly true for adult patients with acquired pathologies, the need for better materials is even more pressing in the setting of congenital heart disease, where any valve replacement activates a ticking clock towards the next procedure. The study by Selcuk et al. is the first to focus on the use of the BioIntegral Biopulmonic Conduit™ on pediatric patients. The authors' main finding is a high incidence of fever in the early postoperative period (>30%), not previously described in the literature.
The pathophysiology of the fever in these patients was not clarified.
No clinical or echocardiographic evidence of prosthetic endocarditis was found in those who experienced fever; however, the authors point out that this triggered potentially inappropriate antibiotic use and caused prolonged hospital stay. Furthermore, there seems to be a correlation between fever and early conduit stenosis.
To put these findings into the correct perspective, a few aspects must be mentioned. This is a retrospective, single-center study with no control group and a relatively small number of patients; the indirect evidence that no patient had fever after switching to bovine jugular vein conduit does not come from a statistical analysis and it must be considered at best as speculative. in the present study, all conduits were implanted in an extraanatomic position (i.e., in a non-Ross setting), which is a recognized risk factor for early structural deterioration. 10,11 Finally, even if the fever does not always correlate with infection, it always correlates with inflammation, which has been strongly linked to structural deterioration of bioprostheses. 12 Where do we go from here? Better quality research (both preclinical and clinical) in congenital cardiac surgery is needed: a significant proportion of our clinical practice still derives from singlecenter experiences and suboptimal observational studies. Outcomes for the available biological conduits for RVOT reconstruction are rather unsatisfactory. [13][14][15] This, combined with the limited availability of small-size homografts, is the main reason that pushes our interest towards new devices when they become available. However, valve replacement in the pediatric age is the ultimate task for any biomaterial: size, anatomy, and metabolism all plot together against durability. If there are concerns regarding the performance of a biomaterial in the adult population, it is very likely that results in children will be worse.
One may argue that continuing with the current approaches will only provide small improvements. The future is more likely to come from development on the use of biomaterials that act as scaffolds, and which we can repopulate with the patient's own cells. Theoretically, this would be expected to improve durability, but also be the biological substrate for growth, and ultimately reduce morbidity, reoperations, and mortality. Tissue engineering technologies and regenerative medicine have expanded considerably over the last decade, and it may not be long before the translation of this knowledge into clinical practice.
Regretfully till then, after every pediatric RVOT operation, the clock will start ticking.

ACKNOWLEDGMENT
This study was supported by the British Heart Foundation and the NIHR Biomedical Research Centre at University Hospitals Bristol and Weston NHS Foundation Trust and the University of Bristol.