Use of homograft was first reported by Ross and Somerville [3] in the RVOT reconstruction of tetralogy of Fallot and pulmonary atresia in 1965 and is gold standard in the western countries [4]. In Japan, the use of homograft is not popular because of the shortage of donors.

Mechanism of conduit failure includes conduit stenosis, conduit regurgitation, aneurysm formation, and infectious endocarditis. The majority of the conduit replacements were due to conduit stenosis, valvular stenosis mainly due to leaflet calcification, distal anastomosis stenosis, sternal compression, and somatic outgrowth [5–9]. Conduit stenosis was responsible for failure in 53% of patients, technical issues accounted for 30%, and only 8% failed as a result of somatic outgrowth [10]. Durability of homograft conduit is related to patient age and homograft size. Infants showed a disappointing rate of freedom from conduit failure (42%) in comparison with older children (87%) at 5 years [4]. Smaller conduits are generally related to earlier reoperation, but extremely oversized conduit may fail more rapidly due to external compression of the conduit by the closed sternum, valve distortion, and insufficiency with sternal compression or distortion of distal PAs from the oversized conduit [11].

Clinical use of stented xenograft started in the 1970s; porcine valve within a woven Dacron graft as represented by Carpentier-Edwards porcine-valved conduit^® (Edwards Lifesciences, Irving, CA, USA) (Fig. 9.6a) and Hancock porcine-valved conduit^® (Medtronic, Minneapolis, MN) (Fig. 9.6b).

Schiralli et al. [12] reported excellent longevity of Carpentier-Edwards porcine-valved conduit used in the RVOT reconstruction; freedom from reoperation was 70.3% at 8.2 years. The increase in transconduit gradient over time was inversely proportional to conduit size, but the patients receiving large sized conduits (25 and 30 mm) demonstrated no gradient development over this follow-up period. They concluded that Carpentier-Edwards porcine-valved conduit showed excellent longevity at intermediate-term follow-up. Belli et al. [13] reported that freedom from reoperation in Hancock porcine-valved conduit was 98% at 1 year, 81% at 5 years, and 32% at 10 years. They concluded that the Hancock valved conduit is a safe and reliable conduit.

Medtronic Freestyle^® stentless porcine bioprosthesis (Medtronic, Inc., Fridley, Minnesota, USA) (Fig. 9.7), a representative stentless xenograft valved conduit, is derived from a porcine aortic root. It is extensively used in the aortic position, and the report of its use as a RVOT conduit has first published in 2001 [14]. Dunne et al. [15] reported satisfactory short-term outcomes, including functional status and freedom from reintervention based on the meta-analysis of 13 observational studies, including 334 patients with a mean follow-up of 34 months (range 10–98 months); structural valve deterioration occurred in 4.8%, and reintervention was required in 1.1%.

Contegra^® (Medtronic, Minneapolis, MN) is a bovine jugular vein graft comprised of a trileaflet venous valve with three natural sinuses (Fig. 9.8). This conduit is stored in buffered glutaraldehyde and is available in sizes from 12 to 22 mm and has been widely used recently [16]. The main advantages of this conduit are use of natural tissue as raw material, unlimited availability, sufficient length at both inflow and outflow, and a favorable in vitro hemodynamic performance due to an effective orifice area [17]. Mery et al. [18] reported that Contegra was associated with a significantly lower incidence of reintervention and replacement compared with homograft and porcine heterograft; overall freedom from reintervention in Contegra at 5, 10, and 15 years was 73%, 45%, and 26%, respectively. Morales et al. [19] reported excellent midterm results of Contegra; 3-year freedom from severe conduit regurgitation was 81%, and freedom from severe conduit stenosis was 100%. Excellent morphology and hemodynamics, and better durability in a medium-term follow-up, were reported with Contegra conduit [20, 21]. In contrast, Göber et al. [17] do not recommend routine use of this material, because of the unpredictable incidence of supravalvar stenosis. Other problems in Contegra have also been reported: high risk of infectious endocarditis, pseudoaneurysm formation at the distal anastomosis, aneurysmal dilatation, extensive intimal proliferation at the level of distal anastomosis, diffuse stenosis by tissue ingrowth, conduit kinking, and compression [18, 19, 22–25]. Freedom from conduit dysfunction and failure were significantly related with younger age, conduit size, and original diagnosis (truncus arteriosus) [18].

Handmade autologous pericardial conduit is also used as an RV-PA conduit. Schlichter et al. [26] reported excellent durability of fresh autologous pericardial conduit with bileaflet valve (Fig. 9.9) in the 54 survivors of RVOT reconstruction who were followed up from 5 to 15 years; freedom from reintervention at 5 and 10 years was 92% and 76%, resulting in 100% at 10 years for conduits larger than 16 mm at the time of implantation. Isomatsu et al. [27] reported that freedom from late events (conduit replacement or late death) was 88.5% at 5 years and 85.4% at 10 years in autologous pericardial valved conduit. Younger age at operation and postoperative pressure ratio from right to left ventricle were predictors of conduit longevity. They recommended autologous valved conduit in RVOT reconstruction when direct anastomosis is not suitable.

Expanded polytetrafluoroethylene (ePTFE) valved conduit is very popular as RV-PA conduit in Japan. One of the reasons for this is that the domestic supply of homograft conduits is extremely rare. There are several types of handmade ePTFE valved conduit: ePTFE trileaflets composed in autologous pericardial roll, in Dacron tube, or in ePTFE tube with bulging sinuses [29, 30]. Ando and Takahashi [31] reported their follow-up results of ePTFE valved conduit composed in Dacron tube; freedom from conduit explantation was 88%, freedom from PR (≤ mild) was 75%, and the pressure gradient across the conduit was 18.1 mmHg at 7 years. Koh et al. [32] compared late results of conduits containing ePTFE trileaflets and whole heterologous pericardial trileaflet conduits; all trileaflet conduits have been free from calcification or important obstruction over a follow-up period up to 7 years. In general, glutaraldehyde-fixed heterologous pericardium was found to have a prominent inflammatory reaction, with calcification and shrinkage. In contrast, ePTFE trileaflet conduit is expected to provide flexible valve behavior along with favorable durability, and when ePTFE leaflets became nonfunctional, they adhered to the conduit wall and became fixed in the open position without resulting in significant obstructive deterioration. Whole ePTFE trileaflet valved conduit with bulging sinuses showed excellent midterm results (Fig. 9.10). Freedom from reoperation at 10 years was 95.4%, and pulmonary insufficiency was mild or nonexistent in 95.0% of the patients. The pressure gradient between the right ventricle and the pulmonary artery was 14.0 ± 13.2 mm Hg [26, 29]. In addition to the good compatibility of the material [33], they believe that the combination of bulging sinuses and fan-shaped valve leaflets contributes to the excellent long-term results of this conduit; bulging sinus generates vortex flow which improves closing property of the valve, and a fan-shaped leaflet makes ideal coaptation. In the comparison with various types of RV-PA conduits (homografts, ePTFE valved conduits, Medtronic Hancock bioprosthetic valved conduits, non-valved ePTFE tubes, and others) for biventricular repair, Shinkawa et al. [34] reported that the significant factors for the freedom from conduit reoperation were age, preoperative diagnosis, conduit size, and conduit material. The freedom from conduit reoperation at 5 years was best in ePTFE valved conduits (92.1%).

Conduit reoperation is indicated for conduit obstruction (calcification or thickening of the leaflets, pseudointimal peel formation), valve regurgitation (laceration, perforation, or shrinkage of the leaflets), infectious endocarditis, formation of aneurysm or pseudoaneurysm, somatic outgrowth, and so on. Among all, conduit obstruction is the most frequent cause of conduit explantation [28, 35–37].

Operative indication for conduit obstruction is usually based on the pressure gradient across the conduit or RV systolic pressure. According to Mohammadi et al. [38], their indication is either (1) conduit pressure gradient (65–70 mmHg) or (2) RV/LV pressure ratio (≥0.8). Dearani et al. [39] reported less value criteria of pressure gradient, 40–50 mmHg. Homann et al. [40] adopted the conduit exchange before the clinical signs of right ventricular failure, when the conduit pressure gradient exceeds 40–50 mmHg. Sano et al. [36] also emphasized the importance of timing of conduit replacement before the appearance of right ventricular failure.