Pulmonary valve replacement is traditionally performed using cardioplegia in order to induce cardiac arrest during the operation. However, the induction of cardiac arrest is known to be associated with several postoperative complications. Therefore, over the years new cardioprotective techniques have been introduced: one of which is the on-pump beating heart technique. The technique of pulmonary valve replacement on a beating heart could be efficacious in reducing the incidence of cardiac dysfunction or injury which can be associated with the use of cardioplegia. Such as the avoidance of aortic cross-clamping observed in the beating heart technique may be linked with lower risks of stroke and other aortic complications. Therefore, the technique that we present combines the advantages of operating on a beating heart and being on-pump in the context of complex re-do operations of the pulmonary valve.
The on-pump beating heart technique of pulmonary valve replacement is safe, easily reproducible, and may confer superior postoperative outcomes in comparison to the cardioplegic surgical technique.
Introduction
Surgical pulmonary valve replacement (PVR) is deemed the most common cardiac operation in adults with congenital heart disease (CHD). , The pulmonary valve is the least likely of the four cardiac valves to be affected by acquired diseases, and therefore, most pulmonary valve disorders are congenital. More specifically, pulmonary valve stenosis accounts for 7% of all children born with CHD and contributes to 80%-90% of all lesions causing right ventricular outflow tract (RVOT) obstruction. , The majority of patients with congenital diseases undergo surgical interventions during childhood to correct congenital heart defects and outflow tract obstructions. However, postoperative valvular dysfunction (POVD) in adulthood is a common complication in this patient population, which has been operated on in childhood for tetralogy of Fallot (TOF), transposition of the great vessels, balloon valvotomy, and repaired truncus arteriosus. With time, the progression of the pulmonary valve dysfunction can lead to right ventricular (RV) dysfunction. For this reason, PVR is considered the most common cardiac operation in adults with CHD. , Despite the lack of specific criteria to indicate the need for PVR surgery, PVR is advised as it is known to improve both patients’ symptoms and RV function.
Traditionally, pulmonary valve replacement is performed by first establishing cardiopulmonary bypass (CPB), followed by the induction of cardiac arrest using a cardioplegia solution. However, inducing cardiac arrest has been related to severe postoperative complications, including impairment of normal myocardial contraction, and subsequently, impaired myocardial fluid homeostasis and end-organ blood perfusion. Additionally, the utilization of cardioplegia during CPB has been shown to demonstrate potential adverse outcomes, including reperfusion injury. Consequently, this led to the development of the beating heart technique which has been associated with a reduction in postoperative complications in comparison to cardiac arrest induced by cardioplegia.
This article presents our technique of on-pump beating heart pulmonary valve replacement, which was developed as a natural evolution of our extensive experience in minimally invasive pediatric and congenital cardiac surgery. This surgical technique combines the benefit of the CPB in providing a bloodless surgical field with the benefits of avoiding the induction of cardiac arrest in addition to minimizing in-patient care time, , reducing cardiac injury, , , and lowering the risks of stroke.
Operative Technique
When designing the operative plan for a PVR, the surgeon must consider the preceding surgical techniques utilized on the patient in order to maximize the surgical outcomes. Moreover, extensive preoperative assessment should be performed to determine the most suitable surgical technique for each patient. These preoperative investigations include a baseline electrocardiogram (ECG), chest X-ray (anterior-posterior and lateral view), transthoracic echocardiogram (TTE), a coronary angiogram, and a computed tomography or magnetic resonance imaging (MRI) of the chest in the case of redo-sternotomy. A perioperative transoesophageal echocardiogram (TEE) is used to establish the baseline parameters including, the size of the pulmonary valve, the size and function of the RV, and the pressure within the RV and pulmonary artery.
Establishment of Cardiopulmonary Bypass in Case of Redo-Sternotomy
In the case of a redo-sternotomy, CPB is established through femoral access using a multi-stage and multiperforated venous cannula, providing optimal venous drainage. Establishing the CPB before the resternotomy allows for a safer reopening of the sternum, and prevents the need for extensive preparation of the surgical field, which augments the risk of intraoperative complications as well as procedural duration. Limited preparation of the heart from adhesions is suggested, however, removal of adhesions on the RV and the pulmonary artery must be performed in order to have a clearer surgical field. The opening of both pleural spaces improves the intraoperative visualisation and reduces the tension amongst structures.
Localisation of the femoral artery and vein under ultrasound guidance is recommended. Incision above the demarcation of the femoral vessels is performed, followed by the preparation of the femoral artery and vein for cannulation. The placement of a pursue string suture around the femoral artery and vein using a 5-0 Prolene is carried out. Under the guidance of the TEE, a multistage-venous cannula is inserted in the femoral vein using the Seldinger technique. The correct positioning of the tip of the venous cannula in the superior vena cava is assessed using the TEE. The arterial cannula is inserted in the femoral artery using a guide wire, Figure 1 . Correct positioning of the arterial cannula in the aorta is confirmed with the use of the TEE.
In the case of redo-operations following TOF and other congenital heart defects, the TEE is used to assess the presence of atrial and ventricular septal defects. This is of clinical importance, as the presence of intracardiac shunts either at the atrial or ventricular level presents a contraindication for the beating heart technique approach. In the presence of a shunt, cardioplegic cardiac arrest is suggested.
Establishment of Cardiopulmonary Bypass in Primary Operations
The patient is prepared as per standard protocol for sternotomy cases. Partial upper sternotomy can also be used in primary operations. The pericardium is incised longitudinally, allowing the exposure of the aorta and pulmonary artery. Following system heparinization with target activated clotting time of greater than 400s, arterial cannulation of the distal ascending aorta using a flexible arterial cannula is performed to maximize the unobstructed exposure of the pulmonary artery. In addition, cannulation of the superior and inferior vena cava (bi-caval) using 1-stage venous cannulas is conducted with appropriately sized cannulas according to the patient’s body surface area, ensuring optimal venous drainage. Following cannulation, the patient is placed on CPB.
Exposure of the Pulmonary Valve
The pulmonary trunk is then opened longitudinally beginning 1 to 2 centimeters from the sinotubular junction towards the pulmonary annulus, extending the incision into the proximal 1/3rd of the RVOT whilst controlling the presence of air in the left heart, Figure 2 . In the presence of minimal or no RVOT obstruction, the incision in the RVOT is kept minimal. The placement of 2 stay sutures on either side of the longitudinal incision at the level of the pulmonary valve allows for maximal exposure of the pulmonary valve for excision, Figure 3 .
