The Ross Konno procedure is a technically demanding operation in neonates and infants, particularly in small babies and those with significant aortic annular and left ventricular outflow tract hypoplasia. There are several key technical considerations for harvesting the pulmonary autograft with care to preserve the left main coronary artery and the septal perforating arteries in addition to ensuring an optimal muscle cuff on the base of the autograft. Accommodation of the autograft deep within the native aortic valve annulus by performing an appropriate Konno incision and ensuring correct suture placement is essential. Adequate epicardial mobilisation and subsequent reimplantation of the coronary arteries into the autograft neo-aortic root is also a key consideration given the significant radial displacement of the coronary arteries required to accommodate the often much larger autograft into the space of a previously very small aortic root. Although the overall technical details of the Ross Konno procedure have previously been described by others the specific granular technical detail and meticulous approach required for a successful procedural outcome in neonates and infants remains to be fully elucidated. Key technical considerations such as suture spacing, positioning of the autograft with in the Konno incision and management of the coronary arteries require detailed description. We describe our institutional approach to the Ross Konno procedure in neonates and infants to clarify these important technical considerations.
Technical considerations are essential to optimize outcome in neonatal and infant Ross Konno procedures with meticulous harvesting and implant techniques to accommodate the autograft in the LV outflow.
Introduction
Critical aortic stenosis in the neonatal and infant age groups continues to be a difficult problem to manage procedurally. Catheter-based balloon dilatation of the aortic valve produces variable results, often with ongoing residual stenosis, particularly in patients with a very small aortic valve annulus and/or a non-tricommisural valve. , Important aortic valve regurgitation may limit the long-term outcome of many patients post-balloon valvuloplasty. Similarly, isolated neonatal or infant surgical aortic valve repair has variable results and addresses only leaflet pathology but not important aortic valve annular hypoplasia resulting in the frequent need for later re-intervention. Ross and Ross-Konno procedures tend to be avoided in neonates and infants as early mortality and morbidity is often high. especially in association with impaired left ventricular function and concomitant mitral valve disease. However, there are important technical considerations unique to this group of patients that may be critical to achieving an optimal, successful outcome with the Ross-Konno procedure in this small size and young age range. Use of a Konno incision is frequently required and there are particular technical considerations for harvesting and implanting the pulmonary autograft with requisite meticulous attention to surgical technique. Some of this detail has been previously described however subtle additional granular surgical detail is very important in these fragile and often small patients. We present the detailed surgical technique and principles used for many of the cohort of neonatal and infant Ross-Konno procedures undertaken at our institution with outcomes recently published by Luxford et al.
Surgical Technique
All cases were approached through a median sternotomy with subtotal removal of the thymus. Myocardial preservation strategies evolved over the 23 years of our published experience from a combination of antegrade and retrograde St Thomas-based blood cardioplegia to antegrade (aortic root and direct coronary ostial) Del Nido cardioplegia more recently. Moderate systemic hypothermia was employed other than for cases that required concomitant aortic arch repair when deep hypothermia was utilised. Prior to establishing cardiopulmonary bypass, the position of the sinotubular junction of the pulmonary valve is noted and the level of the pulmonary artery bifurcation for transection is marked by sharp dissection of the adventitia above the valve commissures and a few millimeters above sinotubular junction ( Figure 1 ). Dissection to delineate the right pulmonary artery origin anteriorly is performed with a view to transecting the pulmonary artery at the level of the bifurcation, leaving a margin of distal pulmonary artery attached to the bifurcation to ensure good growth potential. The actual main pulmonary artery in the neonatal and infant age group is very short but it is important to keep the sinotubular junction of the pulmonary valve intact with a short cuff of main pulmonary artery wall superiorly to accommodate the distal suture line of the autograft with the expected size disparity to the smaller ascending aorta ( Figure 2 ). This is quite different to the approach in older children and adults whereby essentially no pulmonary artery above the sinotubular junction is preserved on the autograft. This ensures that the outflow suture line to the ascending aorta is immediately at the sinotubular junction thereby stabilising this region against dilatation in these older and bigger patients who will inevitably experience higher neo-aortic root pressure than babies.
Arterial cannulation for cardiopulmonary bypass (CPB) is performed high on the ascending aorta near to the origin of the innominate artery. Venous cannulation is bicaval with provision to snare for total CPB. The ductus is encircled and ligated as necessary for neonates. The patient is cooled to moderate hypothermia (28-30°C). The aorta is fully separated from the main and right pulmonary arteries and the sinotubular junction of the aorta is identified. Coronary arterial anatomy is inspected and abnormal coronary positions should be defined as these can occasionally occur in patients with a bicuspid aortic valve.
The ascending aorta is cross clamped just proximal to the arterial cannula. Depending on the degree of native aortic valve regurgitation, antegrade cold blood cardioplegia is delivered via the aortic root or directly into the coronary ostia (with a 16F or 18F intravenous cannula or 2mm olive tip cannula) to induce cardioplegic diastolic arrest and produce electromechanical silence. After the induction dose, myocardial preservation is maintained with retrograde cardioplegia as described below or repeat interval doses of direct coronary ostial cardioplegia can be administered. Coronary ostial Del Nido cardioplegia has a re-dosing interval of 45-60 minutes. When using retrograde cardioplegia the venae cavae are snared and an oblique right atriotomy is performed. A 10 Fr dual lumen retrograde cardioplegia cannula with a manually-inflated balloon is primed and secured within the coronary sinus with a 6/0 Prolene purse string. Direct vision enables placement of the retrograde catheter at the entrance to the coronary sinus, resulting in delivery to both the left and the right coronary systems. St Thomas-based cardioplegia is repeated every 20 to 30 minutes through the cross-clamp period with every second cardioplegia dose given antegrade. This minimises instrumentation of the coronary orifices and provides excellent myocardial protection. A left atrial vent is placed across the interatrial septum (usually through a patent foramen ovale) to scavenge the pulmonary venous return.
After establishment of myocardial preservation, the ascending aorta is transected. It is important to transect the aorta almost at the sinotubular junction (STJ) to preserve the aortic wall thickening around this area on the distal end of the ascending aorta ( Figure 1 ). This will contribute to stabilisation of the neo-aortic STJ during growth and avoid dilatation in this region of the outflow suture line. Note that an aortic valvotomy or valvoplasty may be contemplated as a temporising measure at this point based on the appearance of the aortic valve. In our experience, this group of patients presenting in the neonatal and infant period often do not get reliable long term relief of obstruction with an isolated aortic valve repair. For this reason we consider a comprehensive Ross-Konno operation to be a more robust and predictable solution.
Autograft harvest then is performed under cross-clamp with an arrested heart under optimal conditions to enable excellent visualization. The pulmonary artery is transected just below the bifurcation ( Figure 2 ). Avoid cutting into the branch pulmonary artery origins when performing this distal component of the autograft harvest. The pulmonary root is then mobilised by low voltage electrocautery dissection leaving a thin layer of epicardial fat on it and dissecting down to the infundibular muscle ( Figure 3 ). The separation of the fusion of the cono-truncus is performed with sharp dissection, using fine (tenotomy) scissors; we are not concerned about preservation of the aortic wall which will be discarded anyway, but ensuring that the full thickness of the pulmonary sinus wall is preserved ( Figure 4 c-c).
Once the fusion of the cono-truncus has been crossed the infundibular muscle below becomes evident. This enables the plane between the infundibular sleeve of muscle anteriorly and the interventricular septum posteriorly to become evident. This is an avascular plane ideal for harvesting the autograft and ensuring identification and preservation of the septal perforating branches of the left anterior descending coronary artery. Inspection through the transected pulmonary artery will show that the level of dissection has been carried approximately 2 mm below the nadir of the pulmonary cusps so that the pulmonary valve can be excised as a true cylinder thereby preserving the muscle as thick as possible to support the valve and allow a secure inflow suture line.
The initial horizontal incision anteriorly in the pulmonary infundibulum is made approximately 8mm (in a 3kg neonate or proportional to patient/pulmonary valve size) below the nadir of the anterior leftward (non-facing) pulmonary cusp ( Figure 5 ) and is carried vertically through the thickness of the wall of the right ventricle so that the integrity of the right ventricular muscle is maintained without any thinning. This enables the autograft to be sutured in place with full-thickness sutures that go through the endocardial and epicardial walls of the donor muscle at the same level. When harvesting the autograft, the extra muscle skirt under the left anterior cusp of the pulmonary valve should be left to accommodate closure of the Konno incision ( Figure 4 b-b).
A 2-3 mm clearance from the nadirs of the valve cusps in the free wall is maintained for the remainder of the circumference of the proximal valve harvest all the way around the infundibular free wall to the septum ( Figure 4 a-a). In the region of the septum an incision into the septum for 1mm to 2mm depth is made using a No.15 blade approximately 2-3 mm below the pulmonary valve annulus. Next, starting where the autograft is attached to the septum, scissors are used as in the description of Donald Ross at 45 0 to the infundibular wall ( Figure 6 ) to separate the muscle fibres sharply off the septum and thereby enucleate the autograft with a shallow piece of infundibular muscle. This sharp dissection should be in the avascular plane described above between the anteriorly placed infundibulum and posterior interventricular septum. Damage to the septal perforator of the left anterior descending artery which can be positioned superficially in the septum is avoided by staying in this plane. There must be plenty of conal muscle retained on the autograft to support the valve cusps, but not too much bulk. This allows the autograft to hold its shape and facilitates a secure inflow suture line ( Figure 4 ). Preserving all the endocardium is essential for both preserving the valve leaflets and for suturing autograft myocardium; it makes the autograft as robust as possible.
