Ventricle and a half

Ventricle-and-a-Half Repairs

Introduction

The ventricle-and-a-half repair is used when there is essentially a single functional ventricle, and the dysfunctional ventricle, although not considered of sufficient size to handle an entire cardiac output, is considered to be of sufficient size to handle about half the cardiac output. The operation consists of a superior cavopulmonary anastomosis combined with the connection of the dysfunctional ventricle to the pulmonary artery through either a native or homograft vessel. In the ventricle-and-a-half repair, the atrial septal defect is closed, in order to allow for desaturated inferior vena cava blood to enter the dysfunctional ventricle and flow to the pulmonary arteries. The ventricle-and-a-half repair can be considered the last stage of the functional single ventricle pathway, in that the systemic and pulmonary circulations are entirely separated, and there is no compelling reason to perform a more traditional Fontan operation. A fenestrated ventricle-and-a-half repair can be performed in patients with significant risk factors, and consists of a superior cavopulmonary anastomosis with connection of the dysfunctional ventricle to the pulmonary arteries, along with a 4 - 5 mm snared fenestration in the atrial septum, analogous to that performed for the lateral tunnel fenestrated Fontan operation.

Some decisions need to be made in deciding on performing the ventricle-and-a-half repair versus a two-ventricle repair versus a single-ventricle palliation. Often, candidates for the ventricle-and-a-half repair have both a modified Blalock-Taussig shunt and an atrial septal defect. There can also be pulmonary valve insufficiency if a transannular patch had been previously made. A step-wise investigation will lead to the best operation for the patient. In the operating room or in the catheterization laboratory the following can be done:

A two-ventricle repair can generally be performed if both the modified Blalock-Taussig shunt and atrial septal defect can be safely occluded either in the catheterization laboratory or in the operating room.
A single-ventricle repair should be done if occluding the modified Blalock-Taussig shunt while leaving the atrial septal defect open is not tolerated. This is because the patient would be considered to be almost entirely dependent on the shunt for pulmonary blood flow, and no significant forward flow is likely to be found via the right ventricle.
If occluding the modified Blalock-Taussig shunt is tolerated, but not occluding the atrial septal defect, then either a ventricle-and-a-half repair or take-down of the modified Blalock-Taussig shunt, leaving the atrial septal defect patent, should be considered. The latter option is taken when there is a good likelihood that the atrial septal defect can be closed at a later date.

In the situation where there is pulmonary artery hypertension, a valved conduit should be placed between the right ventricle and pulmonary artery before the above considerations can be made.

Stage I: preparation & cardiopulmonary Bypass

A monitoring line is placed in the groin, and one in the upper veins is avoided.
Standard procedures for re-do sternotomy are carried out (see page *).
Cardiopulmonary bypass is started using bicaval cannulation and single arterial cannulation, and the patient generally cooled to 28 - 32° C.
The superior vena cava cannulation site should be kept high in order to allow for sufficient room to performing the bi-directional Glenn anastomosis.

A straight THI arterial cannula works best for re-do aortas. It is of the proper stiffness, and can be more easily guided into the aorta in these circumstances.
The systemic ventricle is vented with a cannula placed in the right superior pulmonary vein.
Attention is given to cerebral protection and perfusion:
In the presence of significant aorto-pulmonary collaterals, hyperventilation can steal blood from the brain to the lungs, and should be avoided.

The superior vena cava should invariably be cannulated. This is of especial importance when coming of cardiopulmonary bypass when there be may hypotension in the presence of elevated central venous pressure.

Stage II: Dissection

The area between the aorta and the pulmonary artery is dissected at this point. This can be a difficult dissection.
The pulmonary artery is separated from the aorta. The under-surface of the aorta is generally dissected away from the pulmonary artery, as opposed to the converse situation. It is often helpful to start the pulmonary artery dissection on the right side of the superior vena cava, as adhesions in this area may not be as dense as on the medial side of the superior vena cava. The pulmonary artery should be dissected well underneath the aorta, if not on the left side of the aorta, depending on the need, if any, for pulmonary artery angioplasty.

The connection of the superior vena cava and right atrium should be clearly understood and dissected out.

The circumference of the aorta is dissected free, and an umbilical tape placed around it, for later use in retraction.

Great care is taken not to use the electrocautery around the phrenic nerves.
The inferior vena cava and superior vena cava are snared.
The aortic cross-clamp is applied, and the heart arrested with an infusion of cold blood-potassium cardioplegia, (30 cc/kg, repeated about every 30 minutes). A temperature probe is placed in the ventricular septum, and myocardial temperature monitored.

Stage III: atrial septal defect closure

The right atrium is opened, and the edges retracted with silk. Note is made of cardioplegia flowing from the coronary sinus. Myocardial temperature should drop appropriately. The atrial septal defect is closed in standard fashion.
The superior vena cava is divided above the area of the sino-atrial node. The cardiac end is either oversewn or anastomosed to the inferior edge of the pulmonary artery:
Advantages of performing an anastomosis from the cardiac end of the superior vena cava to the pulmonary artery is that inferior vena cava blood can enter the pulmonary arteries in the face of severe right ventricular failure. The disadvantage is that a potentially circular circulation is created, where blood ejected from the right ventricle returns to the right atrium via the pulmonary artery - superior vena cava connection.
The pulmonary artery is opened on its superior edge, facing the cephalic end of the divided superior vena cava. .
The cephalic end of the divided superior vena cava is sewn to the incision made into the pulmonary artery using 7-0 Maxon. The anastomosis may be augmented with a hood of pericardium if necessary. The cardiac end of the divided superior vena cava can be sewn to an incision made on the inferior edge of the pulmonary artery at this time.
The fenestration is placed. A 4 mm hole punch is made into the atrial septum. It is surrounded by a snare of 2-0 Prolene made in the usual fashion.
A 2-0 Prolene suture is place around the cut edge of the fenestration and brought out through the lateral wall of the right atrium. The suture is brought out through a large felt pledget. The Prolene is secured to the cut fenestration edge with three interrupted sutures of fine 4-0 Prolene or GoreTex.
The atriotomy is closed.

Stage IV: Completing the operation

With suction being applied both to the aortic root and the left ventricular vent, and while the coronary arteries are being temporarily occluded, the aortic cross-clamp is removed.
The superior and inferior caval snares are released.
Two pleural tubes and two mediastinal tubes are placed as prolonged pleural effusions not unexpected.
Ventilation is resumed
The superior vena cava line is clamped and the cannula removed. The superior vena cava cannula site is repaired with interrupted 6-0 Prolene if there is any distortion.
The left ventricular vent is removed while a Valsalva is being performed.
Left and right atrial lines are generally needed.
Atrial and ventricular wires are placed.
The fenestration snare is brought out underneath the fasciae in the midline.
The patient is weaned from cardiopulmonary bypass, often on dopamine, 5 - 10 m g/kg/min with or without Inocor at 5 - 10 m g/kg/min after a loading dose of 1 - 2 mg/kg.
The inferior vena cava cannula is removed
The heparin is reversed with protamine
Diagnostic pressures of the aortic root and the superior vena cava are performed. Pulse oximetry is followed. Transesophageal echocardiography is performed.
Most, if not all the pump blood is returned to the patient.
The aortic cannula is removed.
Hemostasis and sternal closure are routine.