Analysis of Monocusp Valve Design for Reconstruction of Right Ventricular Outflow Tract in Tetralogy of Fallot: An In Vitro Study

Abstract

Tetralogy of Fallot (TOF) is one of the most common cyanotic congenital heart diseases (CHD), which accounts for approximately 10 percent of all CHD1, requiring intervention in the first year of life. Cardiac surgeons deemed that outcome of TOF repair depends mainly on relief of pulmonary stenosis, whether infundibular, valvar, pulmonary arterial, or (as is usual) a combination of these in early stage. Complete repair is currently performed with good early and mid-term results. While long-term follow-up results revealed approximately one-third of patients require reoperation, mostly because of pulmonary valve (PV) regurgitation. Postoperative pulmonary valve regurgitation has a particularly adverse effect on late postoperative lung volume and right ventricular function2. More and more evidence proved that pulmonary artery without a valve would be useless. PV function preservation is always the first objective in TOF repair. Alternative approaches to right ventricular outflow tract (RVOT) obstruction relief and PV reconstruction fall into 2 broad categories: valve-sparing root enlargement with or without valvuloplasty, and transannular patch (TAP) with or without monocusp valve. The so-called “monocusp valve” was typically performed with autologous pericardium (AP) or polytetrafluoroethylene (PTFE). The polytetrafluoroethylene monocusp transannular patch (MOTP) has shown better function and durability than AP in both animal model4 and clinical practice. As stated by ISO 5840, the two basic points of a successful heart valve substitute function allowing forward flow with acceptably small pressure gradient and holding back retrograde flow with acceptably small regurgitation. The ideal monocusp reconstruction should be with enough free edge length and coaptation height which is appropriate without any stenosis or insufficiency. The traditional approach of 0.1 mm thick PTFE membrane and judicious monocusp leaflet oversizing to promote valve function has not been systematically studied in an anatomic model to understand the impact of leaflet size, position, and design on valve function. The specific aims of this study are, first to develop a physiologically accurate RVOT model that includes realistic infant’s anatomy for the first time that can undergo virtual surgery in a low-risk environment to compare outcomes for different techniques, and second to refine and assess the monocusp with different designs in this RVOT model over a range of physiologic testing conditions. We demonstrated the utility of this platform for quantitative analysis of artificial pulmonary valvular substitute. This model is valuable and pioneering for in vitro assessment of RVOT-based procedures ranging from pulmonary valve replacement to RVOT reconstruction. The evidence-based results can provide important data to guide our clinical practice.