*3.3.6 Mechanical prostheses*

While bioprostheses are the most commonly used prostheses for PVR, the need for repeat operation is inevitable in children and young adults with congenital heart disease and mechanical prostheses may be considered in selected clinical scenarios to minimize the risks involved with repeat operations. The operative risk of mortality increases from 2% at the first repeat sternotomy compared with 4.7% at a fourth sternotomy [10]. Furthermore, Morishita and colleagues demonstrated a fourth time sternotomy to be a predictor of resternotomy-related injury (hazard ratio, 4.31) [11].

Most of those who are considered for mechanical PVR had a congenital diagnosis and underwent multiple previous sternotomies in the past (**Figure 5**).

### **Figure 5.**

*Computed tomography scan in a patient who underwent multiple previous sternotomies for an initial Rastelli procedure with subsequent multiple pulmonary conduits changes and has a bileaflet mechanical prosthesis in the pulmonary position (white circle).*

Although mechanical prostheses are durable, the need for higher-level anticoagulation carries its own risks, but recent reports suggest that with proper anticoagulation and careful monitoring, the risk of prosthetic thrombosis or dysfunction is low.

The issue of the performance of a mechanical prosthesis in the pulmonary position remains a matter of debate as there are no precise criteria for the selection of patients in whom this prosthesis would be well suited. We believe the ideal patient for mechanical PVR is the patient who underwent multiple previous sternotomies and/or requires anticoagulation for another reason such as a leftsided mechanical prosthesis. This patient population includes those with repaired truncus arteriosus, prior Ross procedure, and occasionally repaired tetralogy of Fallot. Other indications may include those who demonstrated poor durability of bioprostheses.

In every case where a mechanical prosthesis is considered, the ultimate treatment decision is individualized after weighing the risks of reoperation if a bioprosthesis is chosen, with the potential bleeding/thrombotic risks if a mechanical prosthesis is chosen.

## **4. Preoperative evaluation**

Associated defects that commonly need to be addressed at the time of PVR include tricuspid valve repair, patch pulmonary arterioplasties, closure of residual shunts, and arrhythmia surgery.

Preoperative transthoracic echocardiography (TTE), computed tomography (CT) scan, or magnetic resonance imaging (MRI) are routinely performed. Cross-sectional imaging is helpful to determine the relationship of mediastinal structures especially the aorta and/or extracardiac conduits to the sternum and in assessing the pulmonary arterial anatomy. Coronary artery evaluation may be needed in certain circumstances to rule out obstructive coronary artery disease or coronary anomalies especially ones that may change the surgical plan regarding the PVR technique. Hemodynamic data from cardiac catheterization may be needed to complement other studies when there is uncertainty about the anatomy or ventricular function.

Intraoperative transesophageal echocardiography (TEE) is routinely performed before and after cardiopulmonary bypass with or without intraoperative direct pressure measurement across the right ventricular outflow tract.
