Operative Steps for Bidirectional Glenn Procedure: A Guide for Beginners (With a Small Modification)

Single ventricle

Single ventricle consists of a group of disease conditions wherein one of the two ventricles of the heart is not functional. These can be grouped as either morphologic single ventricle (for example, hypoplastic left heart syndrome, tricuspid atresia, and unbalanced atrioventricular septal defect) or physiological single ventricle (such as double outlet right ventricle with non-committed ventricular septal defect). In morphologic single ventricle, one ventricle is hypoplastic, while in physiological single ventricle, even though have two well-formed ventricles and two well-formed atrioventricular valves, it is impossible to correct the underlying defect surgically without rendering one of the two ventricles non-functional.^[1]

A fully developed, functional ventricle consists of an inlet part, along with its accompanying subvalvular apparatus, a trabecular zone, and an outlet portion to a great artery.^[2] Patients with a single ventricle have unbalanced pulmonary and systemic blood flow. However, the overall prognosis of infants with univentricular physiology has improved dramatically over the past two decades, though only as a mode of palliative surgery in a staged manner.^[3]

Surgery

Following neonatal palliation in the form of Blalock–Thomas–Taussig shunt,^[4] most univentricular physiology patients undergo the Glenn procedure. In the classic Glenn procedure, the right pulmonary artery (RPA) was permanently interrupted,^[5] while in Azzolina’s modification,^[6] the earliest account of bidirectional cavopulmonary anastomosis, side-to-side anastomosis of RPA, and superior vena cava (SVC) was done. Later modifications resulted in the currently accepted technique of end-to-side anastomosis of SVC with RPA. The bidirectional Glenn procedure is preferably done through a standard median sternotomy using cardiopulmonary bypass (CPB).^[7] Some surgeons prefer to avoid direct cannulation of the SVC, particularly if the vessel is small, and to perform the cavopulmonary anastomosis during deep hypothermic circulatory arrest. Another technique for the construction of a superior cavopulmonary anastomosis is the use of a temporary shunt between the SVC and the right atrium (RA), which is followed by the proponents of off-pump Glenn procedure.^[8] The ultimate aim of this cavopulmonary anastomosis is to unload the systemic ventricle and hence delay its failing as further as possible.^[9,10] The next and final stage of palliation is completed later on with the Fontan procedure.^[11-15]

Objective

The objective of the study is to provide detailed, yet simplified technical aspects of operative steps of bidirectional Glenn procedure, which is lacking in the published international literature, especially with respect to budding cardiac surgeons.

Sternotomy

After written informed consent, the patient is taken to the operation theater. The patient lies in supine position with his arms secured by his side. The patient is painted and draped and antibiotic prophylaxis is administered intravenously. After midline skin incision and division of subcutaneous tissue, median sternotomy is done. The right lobe of thymus is excised taking care not to injure the innominate vein.

Commencement of CPB

Pericardiotomy is done in the upper half and pericardial stays are taken [Figure 1]. Extrapericardial dissection of SVC is done till the innominate vein. It is deemed best to use scissors for this dissection rather than electrocautery to avoid thermal injury to the phrenic nerve and subsequent diaphragmatic palsy, which is considered an unacceptable complication of the surgery. Heparin is administered. Double aortic purse-strings are taken. After 3 min of heparin, aortic cannulation is done [Figure 2]. RA purse-string and cannulation are done at the atrial appendage and CPB is instituted. This is followed by SVC purse-string and cannulation just below its junction with the innominate vein using the smallest cannula for the body surface area of the patient [Figure 3]. At this stage, the patient is on full CPB and ventilation is turned off. SVC is looped with an umbilical tape and the azygous vein is clipped/ligated and divided. Aorta-pulmonary artery (PA) dissection is done to look for patent ductus arteriosus and it is clipped/ligated.

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Figure 1:

Pericardium opened in the upper half.

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Figure 2:

Aortic cannulation. RA: Right atrium.

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Figure 3:

Venous cannulation. SVC: Superior vena cava, RA cannula: Right atrial cannula.

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Transection of SVC

SVC should be completely free of any kind of soft tissue from the innominate insertion to the SVC-RA junction. A vascular clamp is placed at the distal SVC at the level of lower border of RPA, leaving a stump of SVC with RA making sure not to injure SA node and SA nodal artery (check patient’s rhythm after clamping) [Figure 4]. The SVC loop is snugged. A stay is taken at the anterior aspect of SVC for orientation later on. SVC is divided between the stay and clamp in a beveled manner posteriorly [Figure 5]. The SVC stump over RA is sutured in two layers using 5-0 propene [Figure 6]. Clamp is slowly released and hemostasis is ensured.

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Figure 4:

Clamping the RA end of SVC. SVC: Superior vena cava, RA cannula: Right atrial cannula.

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Figure 5:

Division of SVC. SVC: Superior vena cava.

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Figure 6:

Closure of cut RA end of SVC. SVC: Superior vena cava, RA cannula: Right atrial cannula.

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Preparation of RPA for anastomosis

RPA is dissected free of the surrounding tissues from the main PA to the hilar branches. Lymphatics have to be cauterized to prevent chylothorax in the post-operative period. Two stay sutures are put at the superior aspect of RPA, making sure that after anastomosis SVC should lie perpendicularly to RPA. A C-clamp is placed over RPA and a small horizontal incision is made between the two stay sutures. Incision is extended using a Pott’s scissors to about 25% more than the diameter of SVC. The 2 prolene stays are repositioned across the edges of this incision for better exposure.

Bidirectional Glenn anastomosis

Anastomosis of SVC with RPA is started using a 6-0 double arm prolene suture, with the first bite taken in RPA inside-to-out at its left corner, and a rubber shod is placed at the other end. Then, the needle is passed from outside to inside the SVC at 3 o’clock position [Figure 7]. With subsequent forehand bites, the posterior layer of the anastomosis is completed [Figure 8]. Care is taken near the 9 o’clock corner not to take deep bites, to preserve hilar branches from getting closed in the suture line. Furthermore, the corner is under tension and suture is prone to get cut through at this part. Hence, a few bites have to be kept loose and have to be tightened only after crossing the corner. After reaching the anterior aspect, this arm of the suture is fixed at the drape. Anterior layer of the anastomosis is completed from the other arm of the suture [Figure 9]. C-clamp is released, followed by desnugging of SVC loop and after deairing, the suture is tied. It is imperative that there is no excessive application of force while tying the suture, lest, there should be purse-stringing effect. Lie and hemostasis of the Glenn anastomosis are checked. This method ensures that the knot lies at the anterior aspect of the suture line and not laterally.

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Figure 7:

Orientation of the SVC for better understanding of taking bites of sutures for anastomosis with RPA. SVC: Superior vena cava, RPA: Right pulmonary artery.

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Figure 8:

SVC being anastomosed to opened right pulmonary artery. SVC: Superior vena cava, MPA: Main pulmonary artery.

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Figure 9:

Completed Glenn anastomosis.

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We propose a small modification during the anastomosis to prevent the purse-stringing effect. This is done by interlocking the running suture once under the previous bite after crossing the lateral corner (9 o’clock) of the anastomosis and then continuing with the running suture till the anterior aspect. Similarly, with the other arm of the suture, the running suture is interlocked under the previous bite after crossing the medial corner (3 o’clock).

Coming off CPB and chest closure

The patient has come off CPB and after SVC decannulation, Glenn pressure is checked and the need for antegrade flow interruption is assessed. RA and aortic decannulation is done and mediastinal drain is placed. Protamine is infused and after ensuring hemostasis, the pericardium is closed followed by sternal closure, subcutaneous, and skin closure. Aseptic dressing is applied and the patient is shifted to the intensive care unit.

Limitations of the modification

There is no technical limitation regarding this technique, since there is no additional learning curve or expertise required for it and there is essentially no prolongation of the CPB time. There is no change in decision-making for this technique as far as anatomical variables are concerned, for example, SVC size or branch PA anatomy. There are no separate anatomical or surgical exclusion criteria for this modification.