There are two primary approaches to placement of a pulmonary valve. The “gold standard” is a surgical replacement of the valve. The main benefits of a surgical approach are that the valve can be placed with very little morbidity and mortality but requires open-heart surgery, and placement on cardiopulmonary bypass. Additionally, surgically placed pulmonary valves may require subsequent reintervention in certain patients [8]. Surgical intervention allows other anatomic issues to be addressed, such as pulmonary artery stenosis and closure of residual shunts. Batlivala and colleagues have illustrated that surgical PVR is associated with low mortality rates, demonstrating a 5-year mortality rate of 1.3% among 254 patients [9]. Alternatively, surgical PVR requires longer hospitalization periods and increased rates of blood transfusion in comparison with other PVR techniques [10].

Recently, there has been the development of percutaneous pulmonary valve replacement (PPVR), with the benefit of not requiring open-heart surgery [11]. Patients are able to be discharged the next day and do not typically have to undergo surgical reintervention. Additionally, this approach to valve placement maintains the valvular competency and is associated with very low rates of mortality [12]. However, this approach is only for patients with previous conduit placement during their repair, approximately 15% of all tetralogy of Fallot patients. In PPVR, the device currently in use cannot be used in patients with an outflow tract that has a diameter greater than 22 mm [12]. This approach can be limited by patient size, complex anatomy, and vascular access. It is reserved for simpler cases as other anatomic issues cannot be simultaneously addressed. Overall PPVR is minimally invasive and reduces the risk of postsurgical complications, decreases hospital stay, and improves outflow hemodynamics in patients [13].

To address the limitations of both surgical valve placement and PPVR, adapting a “perventricular” approach (placing a large sheath via the apex of the right ventricle) has been developed. In the last few years, perventricular access has been widely accepted and used for muscular ventricular septal defect (VSD) closures [14–16]. As the largest study to date, Xing and colleagues reported on VSD closures in 408 pts with a success rate of 96.3% and a complication rate of less than 4%. Complications included trivial pulmonary regurgitation and incomplete right bundle branch block [16]. Though this approach is not currently being widely used for pulmonary valve implantation, much success has been reported in the literature [17–19]. The mainstay of this less invasive approach is the avoidance of cardiopulmonary bypass with minimal or no complications, providing direct access to the RVOT without compromising the tricuspid valve, sustaining injury to a femoral vessel, or risking damage to the valve [20].

3D printing using additive manufacturing to produce anatomically correct models of the RVOT helps to plan both the surgical approach and catheter-based approach. Dr. Charles Hull in the mid-1980s invented stereolithography (STL) [21] to produce solid objects from digital files using a process involving curing of liquid photopolymer using ultraviolet laser [22]. From this initial work, the field of 3D printing or rapid prototyping began.

Rapid prototyping in medicine has had great success and is a rapidly growing field. It has been very valuable for the planning of procedures. Armillotta et al [23] reported using rapid prototyping models in the planning of percutaneous pulmonary valves. They reported that the three specific applications were (1) diagnostic visualization, (2) surgical planning, and (3) implant fabrication [23]. The use of 3D printing to aid complex surgical planning has been gaining popularity in particular for congenital heart disease [24, 25]. The biggest limitations in early reports of cardiac modeling are the lack of detail related to thin mobile structures such as the atrial septum and valve tissue [24], and the challenge of demonstrating improved clinical outcomes using rapid prototyping [26]. With the improvement in 3D printing techniques and the materials used, surgical and interventional planning can be greatly improved [27].

The 3D printed RVOT and proximal branch pulmonary arteries allow for interventional staging. We reported our experience using a 4-step approach for planning of replacement of the pulmonary valve [28]. The algorithm we use involves the 3D printed outflow tract and aids in interventional planning, giving us the ability to decide between a percutaneous or perventricular approach.

The perventricular approach combines the skills of both the interventional cardiologist and the surgeon in what is referred to as the “hybrid” approach. This technique has been proven to be safe, effective, and beneficial [15].

We reviewed all patients referred to us for PVR, for suitability, for trancatheter, for surgical, or for perventricular valve placement. The evaluation included echocardiography and magnetic resonance imaging (MRI). In all patients, the MRI data were used to produce a 3D model of the RVOT using postprocessing software (Materialise^®). One representative model is shown in Fig. 10.2.

All patients were treated in the “hybrid” catheterization laboratory with cardiopulmonary bypass on standby. Patients underwent right and left heart catheterization with balloon sizing of the outflow tract, 3D rotational angiography, and coronary evaluation during balloon sizing.

Patients underwent routine surgical preparation that included preparing for a full sternotomy. In all patients, a perventricular approach was used, via a subxiphoid incision and accessing the RV diaphragmatic surface. For the perventricular approach, a micropuncture needle [Cook Medical Micropuncture Introducer Set: 21 g/7 cm:  5.0 fr/10 cm: 0.018/40 cm wire (Ref #: G43870)] was then placed and a wire placed into the RVOT under transesophageal guidance. After confirming the location, two 4-0 polypropylene sutures with felt pledgets purse strings were placed around the wire with approximately a 1 cm diameter. A six-French sheath [Terumo Pinnacle introducer sheath 6 fr/10 cm 0.038 guidewire (Ref #: RSS602)] was placed over the wire, and the wire was exchanged. A delivery sheath was placed over the wire into the RV, and RV outflow stent(s) were placed to produce an appropriate landing zone for stented valve placement. Heparin was administered to an ACT >200.

Postdeployment angiography and pull back were performed to determine angiographic regurgitation and valve stenosis. Intracardiac echocardiography was performed to determine degree of pulmonary regurgitation and stented valve instability. In the first 2 patients, no chest tubes were used. The remaining 6 patients had 24 Blake drains placed.

Demographic information for our patients is summarized in Table 10.1. Eight patients were treated with perventricular pulmonary valve placement. Table 10.2 reviews the catheterization information for the patients. There were two complications that occurred. One patient developed a preperitoneal collection that needed to be drained by interventional radiology, and another patient developed a pericardial effusion that required drainage. Three patients had disruption of secondary chordae that lead to mild tricuspid regurgitation. There was dramatic improvement in pulmonary artery diastolic blood pressure postimplant, 10.2 ± 2.0 mm Hg compared to RV diastolic pressure preimplant, 3.8 ± 1.8 mm Hg (p = 0.003). All patients had severe regurgitation, preimplant. There was no significant gradient from RV to pulmonary artery with a mean gradient of 2.3 ± 1.0 mm Hg post-implant.