Ventriculoatrial Shunt Placement Technique

Before preparing the field, perform a trial fluoroscopy to be certain that the appropriate anatomic landmarks are easily visualized.

In order to prevent backflow of blood and subsequent thrombosis and catheter occlusion, flush the distal catheter with heparinized saline immediately before connecting it to the proximal aspect of the system, and occlude the catheter until it is connected. Place the distal tip of the atrial catheter in the middle to lower atrium, approximately at the level of T6.

Administer antibiotics preoperatively, and adhere to sterile technique to minimize the risk of infection. ^[7]

Placement of the ventricular catheter does not differ significantly from that in other cerebrospinal fluid (CSF) shunt operations. In other shunt cases, the authors choose to place the ventricular catheter as one of the final steps in the procedure in order to minimize the risk of dislodgment. However, in the case of a ventriculoatrial shunt (VAS), the authors place the ventricular catheter and valve before accessing the distal vessel in order to minimize the risk of distal catheter malposition or backflow.

If the ventricular catheter is placed frontally, a length of distal shunt tubing is secured to the outflow port of the unidirectional shunt valve. A 1-cm vertical retroauricular incision is made, and the tubing is pulled subcutaneously out through this incision. A hemostat or temporary suture is placed to prevent CSF egress. If the ventricular catheter is placed through an occipital burr hole, the distal shunt tubing is tunneled directly to the proposed site of entry for vascular access.

A percutaneous (Seldinger) or open vascular cutdown technique may be used to access the appropriate vessel for atrial catheter positioning. The authors prefer a percutaneous technique, which is similar to that used for the placement of central venous catheters. Ultrasonographic (US) guidance may be used to facilitate access. ^[8]

The internal jugular vein (IJV) is the most commonly selected access vessel. An appropriately sized (often 20- or 22-gauge) needle is used to puncture the skin one to three fingerbreadths (depending on the size of the patient) above the clavicle, between the heads of the sternocleidomastoid muscle. If subclavian vein access is chosen, the entry site is inferior to the clavicle, at the junction of the middle and lateral third of the bone.

After successful cannulation of the vessel, a flexible guide wire is passed through the needle, and the tip is positioned in the superior vena cava (SVC) or the cardiac atrium under fluoroscopic guidance. Instability on electrocardiography (ECG) may indicate that the guide wire is positioned within the heart.

The needle is then removed, and a nick incision is made to facilitate dilator entry. The authors prefer to load the peelaway sheath on the dilator and pass them together into the vessel. Occasional advancing and retracting of the guide wire ensures that the dilator is following the wire’s subcutaneous course.

The dilator and guide wire are then removed, and the shunt tubing is passed down the peelaway sheath. Brisk back-bleeding is often encountered upon removal of the dilator. The authors find it most effective to pass the distal shunt well beyond the lower atrium before splitting and removing the peelaway sheath; it is not always possible to advance the shunt tubing once the sheath is removed. The catheter is then pulled back to an appropriate final position (as described in more detail below), flushed with heparinized saline, and connected to the proximal shunt system.

An open approach can also be used to gain access to the vascular system. A cutdown is made to the IJV, where a purse-string suture is placed on the anterior wall of the vein. A stab incision is made inside the purse-string, and the catheter is placed directly into the vein. The suture is then tied down around the catheter to stop any back-bleeding.

A third technique is to isolate the transverse facial vein as it enters the IJV. This vein can then be divided and the shunt passed down into the IJV. A tie is used to secure the catheter to the transverse facial vein and to prevent back-bleeding.

The position of the distal catheter tip is verified by means of fluoroscopy. The tip of the distal catheter is optimally positioned in the middle to lower atrium, at approximately the T6 vertebral body level. If the tip is not clearly visualized, injection of a small volume of radiopaque contrast material may facilitate fluoroscopic visualization. Other techniques, including recording pressure waves through the catheter ^[9] or using the catheter as an ECG lead, ^[10] may also be used.

Once satisfactory positioning of the atrial catheter has been achieved, the proximal and distal catheters are trimmed in such a way as to allow a small amount of redundancy. Excellent flow of CSF through the proximal catheter system is verified, and the distal catheter is flushed with heparinized saline and connected to the proximal catheter via a straight connector. The incisions are thoroughly irrigated with antibiotic-impregnated saline and closed in layers.

Complications of VAS placement may include the following:

• Shunt-induced immune-complex glomerulonephritis - Chronic shunt infection with Staphylococcus epidermidis may result in immune complex deposition at the renal glomerulus, causing severe glomerulonephritis; this injury generally responds immediately to externalization of the shunt and appropriate antibiotic therapy
• Pulmonary hypertension due to microemboli - A catheter within the cardiac atrium may casue chronic microembolization and thus result in pulmonary hypertension
• Endocarditis
• Wound/CSF shunt infection ^[7] - CSF shunt infection rates vary but are commonly reported to be in the approximate range of 5-8%; a CSF shunt infection warrants removal of the shunt and placement of an external ventricular drain during antibiotic treatment of the infection
• Outgrowing the shunt - As a child with a VAS grows, the shunt will slowly back out of the atrium, a process that potentially leads to shunt malfunction
• ECG instability
• Shunt malfunction - All shunts are prone to malfunction, at a rate of 40% in the first 2 years after insertion or revision; patients and their families should be aware of this and take appropriate action should it occur
• Delayed intracranial hemorrhage ^[11]

SVC thrombosis is a rare complication of VAS placement. ^[12]  Intramuscular migration of the venous catheter is also quite rare but has been reported. ^[13]  Migration of the distal catheter into the pulmonary arteries has been observed. ^[14]  A migrated catheter may be managed via an open or an endovascular approach. ^[15]