Editorial Comment: Reconstruction of the right ventricular outflow tract: short-term solutions, long-term problems

Abstract

There is no reliable, durable valve conduit for reconstruction of the right ventricular outflow tract in conditions such as Fallot’s tetralogy, pulmonary atresia, truncus arteriosus and for pulmonary valve replacement after the Ross procedure for aortic valve replacement. All the reconstructions available provide short-term unobstructed flow with no pulmonary incompetence but in the mediumto long-term there is the development of either right ventricular outflow tract obstruction and/or severe pulmonary incompetence. Currently, the answer to these problems is reoperation with pulmonary valve replacement, usually at an open operation or in some cases with a transcatheter-mounted valve placed in the right ventricular outflow tract. Historically pulmonary or aortic homografts have been the mainstay of valve replacement in the right ventricular outflow tract, either as valves or as conduits. Various animal-derived valves, usually glutaraldehyde-preserved valves from cows or pigs, have also been utilized. All of these conduits are dead tissue and are subject to degeneration. There is a variable availability of homografts, in particular, which are usually available in North America and Europe but may not be available in countries like Japan. Ethnic and social considerations also govern the availability of donated tissues. There are also certainly cost implications when homograft tissues in North America may cost in excess of 4000 dollars. In addition to cryopreserved or off-the-shelf products, individual centres have also developed their own techniques for reconstructing conduits and valves in the right ventricular outflow tract, reflecting the availability and cost of complete valve conduits in a particular country. The common conditions whereby a reconstruction is necessary are Fallot’s tetralogy and pulmonary atresia, and in these conditions the alternatives are a non-valved patch in the outflow tract, a monocusp, bicuspid or valved conduit reconstruction. Our own experience in Birmingham, with conduit reconstruction, utilizing new conduits, direct anastomosis without conduits or the use of small animal valve conduits has not been entirely satisfactory [1, 2]. Early competency of the outflow tract and recovery following surgical repair has been satisfactory, but shortterm follow-up has been very disappointing with early failure. We have not had experience of handmade bicuspid or monocuspid valves in the right ventricular outflow tract and have usually used, when necessary, a monocusp from either an aortic or pulmonary valve conduit. Again the short-term results of these have been satisfactory, we have yet to follow up in detail patients in the longer term. Other centres have been more adventurous in their development of tailor made pathways from the right ventricular to the pulmonary artery, and in this journal Oda et al. [3] report a tailor-made PTFE monocusp construction to replace the pulmonary valve in the Ross procedure. The posterior wall of the reconstruction is native pericardium with a 0.1-mm PTFE tailormade monocusp anteriorly roofed over by a 0.6-mm PTFE patch. They report 38 patients divided into two groups, the group with the PTFE patch and a PTFE monocusp had a freedom from pulmonary incompetence of 74.3% at 5 years and demonstrated satisfactory monocusp function in 79.2%. The group with the PTFE patch placed anteriorly instead of the pericardial patch faired better, probably due to a more rigid base for the PTFE monocusp. The monocusp reconstruction of the right ventricular outflow tract is quite a favoured method of tailor-made valve. There are a range of tissues that can be used, from aortic valve and pulmonary valve monocusps through to native pericardial monocusps, bovine pericardial monocusps and Gore-Tex monocusps. Other surgeons have also designed variations on the PTFE monocusp, varying from centre to centre in their techniques. Iemura et al. [4] describe 19 patients having a PTFE monocusp placed for reconstruction of the right ventricular outflow tract. In eight patients at 3-year follow up, two had distal stenoses, two had moderate pulmonary incompetence, however, five patients still had good cusp mobility. Vricella et al. [5] describe their experience with different types of PTFE in lamb models and showed that, at the time of lamb death, 50% had mobile leaflets but two-thirds had moderate or severe pulmonary incompetence. They felt, in this experiment, that the closed PTFE microstructure was better, with less inflammatory response. A 12-year experience with the PTFE monocusp outflow tract reconstruction was described by Brown et al. [6] and, before that, they had described the method of construction and early results, by Turrentine et al. [7, 8]. In the 12-year follow-up, there were 192 patients operated on up to 2006, freedom from pulmonary incompetence of greater than moderate was 86% at 1 year 68% at