Deep Dive Into Aortic Surgery: Mini-Bentall Procedure—Mechanical Valve Conduit

The Bentall procedure is a cardiac surgical operation involving composite graft replacement of the aortic valve, aortic root, and ascending aorta, with reimplantation of the coronary arteries into the graft. This technique was first described by Hugh Bentall and Antony De Bono in 1968, using a median sternotomy approach (1). To minimize surgical trauma and enhance patient recovery, cardiac surgeons are increasingly performing aortic valve replacement via upper hemi-sternotomy or right mini thoracotomy incisions. The mini-Bentall procedure consists of an aortic root and ascending aortic replacement with reimplantation of coronary buttons performed via an upper hemi-sternotomy. The skin incision extends from the angle of Louis to the third intercostal space, usually measuring 4-6 cm in length depending on the body size of the patient. Through this incision, it is possible to perform isolated aortic root surgery or in conjunction with hemi-arch replacement. This  video article describes the technical details on how the author performs a mini Bentall procedure using a mechanical valve conduit, recorded with a high resolution 4K camera system. 

Computed Tomography 

A careful review of CT images of the thoracic aorta in relation to the sternum and the rib cage is necessary. This greatly facilitates the planning for the upper hemi-sternotomy. The upper hemi-sternotomy should be terminated at either the third or the fourth (for bicuspid and aortic-mitral calcifications) intercostal space. The degree of aortic wall calcification and evidence of atheromatous disease are evaluated in both contrast and non-contrast phases. A decision regarding the most appropriate cannulation strategy is sought with the aim to minimize potential embolic risks. 

Preparation 

Following induction of anaesthesia, a radial arterial pressure monitor line, central venous line, pulmonary arterial sheath/catheter and urinary catheter are inserted. The patient is placed in the supine position. The body surface anatomy is clearly marked with a permanent marking pen depicting the positions of suprasternal notch, sterno-manubrial junction, second to fourth intercostal spaces, the inferior extent of xiphoid cartilage, and bilateral femoral arteries. The body is painted with an antiseptic solution. Sterile drapes are placed, exposing the precordium laterally to the mid-clavicular lines and bilateral groin regions. 

Skin Incision 

A midline skin incision is performed from the manubrio- sternal junction to the level of the third intercostal space. The incision is usually 4-6 cm in length depending on the body size of the patient. It is developed through the subcutaneous fat onto the body of the sternum using a diathermy. A cutaneous flap is developed with a diathermy hand-piece along the prepectoral fascia. This flap is extended superiorly above the supra-sternal notch and laterally to the limits of the sternum. A Kocker retractor is used to elevate the skin flap superiorly to expose the bridging vein over the manubrium and inferiorly to the fourth intercostal space. The bridging vein is clipped and cut. A 14 Fr drain is inserted through the skin below the xiphoid and positioned in the subcutaneous space. This is used for CO2 inflow during the case to prevent air embolism and as a subcutaneous drain at the completion of the operation. 

Mini Sternotomy 

A mini sternotomy is performed using a handheld electrical saw from the superior extent of the manubrium. The division is terminated to the left para-sternal space in a reverse “J” fashion. Hemostasis is achieved by applying a small amount of wax to the bone marrow. The thymic fat pad is completely mobilized to the innominate vein superiorly. The pericardium is opened longitudinally to the pericardial reflection superiorly and the level of the right atrial appendage inferiorly. Three pericardial traction sutures are placed on each side, hitched up, and tied securely to the edges of the skin incision. A minimally invasive sternal retractor is placed over the pericardial edges and opened up gradually. In doing so, the sternum is spread open, together with the pericardium, which anteriorizes the ascending aorta. 

Cannulation Strategy 

A vacuum-assist device is built in the cardiopulmonary bypass (CBP) circuit to maximize venous drainage. Full systemic heparinization is achieved with activated clotting time (ACT) greater than 450 seconds. Peripheral venous cannulation is established first using a Seldinger technique. After puncture of a femoral vein, a guide wire is passed up to the superior vena cava. The position of the wire is confirmed with transesophageal echocardiography (TEE) through a bicaval view. The femoral vein puncture site is then progressively dilated. A 25 Fr multi-stage venous cannula is introduced. The pointy-tipped insert is not advanced further once it enters the right atrium. Only the venous cannula itself is now advanced forward over the insert, strictly under the TEE guidance. It is essential that the cannula tip be placed in the superior vena cava to ensure satisfactory bicaval venous return. The venous cannula is subsequently connected to the CPB circuit. 
Arterial cannulation can be established either via distal ascending aorta or femoral artery. In this video article, a distal ascending aortic cannulation is depicted. Two 2-O Ti-Cron purse strings for the aortic cannula are placed in the distal ascending aorta at the level of pericardial reflection. The aorta is carefully cannulated with an elongated one-piece arterial (EOPA) cannula (Medtronic Inc, Minneapolis, MN, USA), which is secured in position and connected to the CPB circuit. 
Systemic temperature is maintained at 32 degrees centigrade for aortic root replacement or 25 degrees if hemi-arch replacement is anticipated. In the latter, splitting the arterial line is necessary beforehand to provide additional cerebral perfusion.

Aneurysm Resection 

Under a low-flow condition, an atraumatic aortic cross-clamp is applied across the distal ascending aorta. Diastolic arrest is achieved with antegrade cardioplegia delivered via a DLP aortic root cannula (Medtronic Inc, Minneapolis, MN, USA) or direct coronary ostial balloon tip cannula (Maquet Getinge Group, Rastatt, Germany) in the presence of aortic regurgitation. Either cold blood cardioplegia solution or custodial cardioplegia solution is suitable. 
After aortotomy, the blood in the aortic root is salvaged. The aneurysmal segment of the ascending aorta is resected, leaving 1 cm cuff of aortic tissue proximal to the cross clamp and 1 cm above the sinotubular junction. The inside of the aortic root is assessed, and the positions of the coronary arteries are visualized. The aortic root is carefully mobilized circumferentially. First, the non-coronary sinus is resected, leaving a 1 cm rim of aortic wall just above the non-coronary annulus. Then, the right coronary button flap is prepared. Two vertical incisions are made from the sinotubular junction down along both sides of the right coronary ostium and connected inferiorly. Often, only limited mobilization of the coronary buttons from the surrounding connective tissue is required. 

Aortic Root Exposition 

In order to provide an excellent exposure, the aortic root is brought in a cephalad direction. This is achieved by putting the pledgeted 2-0 Ti-Cron horizontal mattress sutures above the commissures. These three commissural traction sutures are hitched up and snared in position. This simple manoeuvre provides an excellent exposure of the aortic valve for the minimal access surgical approach (the “Crane” manoeuvre). 

Aortic Root Implantation 

The aortic leaflets are resected, and the aortic annulus is decalcified. 2-0 Ti-cron annular sutures with or without pledgets are used. Horizontal mattress sutures are placed neatly below the aortic annulus. Pledgets are used to reduce the tension created by the sutures when the valve conduit is tied down, especially at the nadirs. The placement of these sub-annular sutures needs to be precise, both in terms of the spacing and whether the needle is passed through the annulus at a perpendicular angle. The sutures are evenly distributed. 
The annulus is sized for its intra-annular and supra-annular dimensions. An appropriate valve conduit is selected. It is advisable not to oversize the valve. The annular sutures are passed through the sewing cuff of the prosthesis. Once all the sutures are passed through the sewing cuff, they are clipped and cut. The valve conduit is parachuted down by gently pulling the sutures vertically upwards with one hand and firmly pushing the valve conduit down onto the annulus with the other hand. Before tying each suture, it is important to check that there are no redundant loops of the sutures below the sewing cuff. The sutures are tied and cut one by one, starting from the three sutures at the nadirs of the annulus to ensure that the prosthesis is seated properly to the lowest points of the annulus. Then, the remaining sutures are tied and cut around the sewing cuff. 
An additional hemostatic layer around the aortic annulus can be achieved with using a 4-0 running prolene suture that incorporates the remnant of the aortic wall and the sewing cuff of the valve conduit. This will improve the hemostasis and reduces blood produce transfusion post bypass.

Coronary Button Re-implantation 

The left coronary artery button is rested in its anatomical position. The appropriate site on the Valsalva graft (Vascutek Ltd, Renfrewshire, Scotland) for left coronary button re-implantation is determined. A Bovie electrocautery (Bovie Medical Corporation, Clearwater, FL, USA) is used to create a circular hole for receiving the left coronary button. The coronary button is trimmed, left with a 3 mm circumferential cuff and re-implanted using a 5-0 running polypropylene suture. The cuff of the coronary button needs to be attached snuggly to the outside of Valsalva graft. 
In a similar fashion, the right coronary button is prepared and re-implanted. The appropriate site on the Valsalva graft for right coronary button re-implantation is determined with the heart fully loaded, so that there is no tension or rotation of the right coronary button anastomosis. Once the position of the anastomosis is marked, the heart is offloaded.  It is imperative to ensure that a full thickness bite with each stitch is achieved. Systemic rewarming is subsequently initiated. 

Distal Anastomosis 

The distal aortic anastomosis is reconstructed with the aortic cross-clamp on. The length of the graft is determined by filling the heart up and pulling the graft upwards on a stretch to meet distal ascending aorta. The graft is trimmed and anastomosed to the distal ascending aortic cuff by using a 3-0 running polypropylene suture. The anastomosis is started from the point furthest away from the operating surgeon. The posterior wall is completed first from 4 o’clock to 11 o’clock position on the aorta. A nerve hook is used to tighten the posterior wall suture progressively towards the operating surgeon. The anterior half of the anastomosis is completed by picking up the other end of the suture and sewing towards the operator. An aortic root vent is inserted before the two ends of the suture are tied. The table is put in a Trendelenburg position, the heart is filled and lungs are inflated, the arterial flow is turned down, aortic cross-clamp is released, and the graft is de-aired from the aortic root vent.

Completion 

A bipolar temporary pacing wire is inserted in the epicardium over the right ventricular outflow tract. Two 28 Fr soft drains are inserted and brought out below the xiphoid cartilage. Hemostasis is carefully checked and the patient is weaned from CPB. Protamine is given to reverse the Heparin effect. Topical Floseal Hemostatatic Matrix (Baxter Healthcare, Zurich, Switzerland) is applied around the anastomotic sites. The surgical site is packed with small gauze sponges for a period of ten minute hemostatic pause. Once the hemostasis is deemed satisfactory, three stainless steel wires are used to approximate the sternum. No. 1 Vicryl suture is used to close the fascia and the subcutaneous fat. The skin is closed with a 5-0 Monocryl subcuticular suture. This completes the mini-Bentall procedure. 

References

1. [Bentall H, De Bono A. A technique for complete 12. replacement of the ascending aorta. Thorax 1968;23:338-9. ]

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