Ventriculoatrial Shunt Placement

Ventriculoatrial shunt (VAS) placement enables cerebrospinal fluid (CSF) to flow from the cerebral ventricular system to the atrium of the heart. This procedure is indicated for hydrocephalus, which is among the most common conditions encountered in neurosurgical practice.

There are multiple potential anatomic configurations for CSF shunts. Most commonly, a catheter is positioned within the cerebral ventricle (the proximal site) and connected to a unidirectional valve that limits flow based on pressure or flow rate. The outflow port of the valve is connected to another length of catheter, which is passed subcutaneously to a space within which CSF can be absorbed (the distal site).

The preferred distal site is the peritoneal space (ventriculoperitoneal shunt [VPS]), in that this space is generally safely accessible and possesses more than adequate absorptive capacity for the CSF volume produced by a given person. In rare cases, the peritoneal space is inadequate, necessitating the use of an alternative distal site. The most common of these alternative sites are the cardiac atrium (VAS ^[1] ) and the pleural space (ventriculopleural shunt).

The primary consideration in any patient who may undergo VAS placement is whether the patient has symptomatic hydrocephalus that necessitates CSF diversion. If so, the surgeon must rule out the peritoneal space as an acceptable location before selecting the cardiac atrium as the site for the distal catheter. Common reasons for this include previous intra-abdominal infection and scarring due to prior procedures or intra-abdominal pathology. Once the peritoneum is ruled out, the surgeon must verify that the atrium is an acceptable target.

Thrombosis of the feeding jugular or subclavian veins may preclude successful access to the cardiac atrium. Long-term thrombosis or previous instrumentation of these vessels can lead to scarring and permanent occlusion. Doppler ultrasonography (US) can be used to effectively evaluate the patency of these large veins if this is of concern. The presence of other intravascular devices (eg, a peripherally inserted central catheter [PICC] line or indwelling central venous catheter) may complicate placement of the shunt catheter or removal of either catheter.

Other considerations include whether the pleural space might represent an adequate alternative. In children younger than 4 years and in patients with poor pulmonary reserve, the pleura may not provide the necessary CSF-absorbing capacity.

VAS placement is indicated for patients with shunt-dependent hydrocephalus in whom the peritoneum is not an acceptable site for distal catheter placement; it may also be considered for patients who do not improve with VPS placement. ^[2] Some surgeons may prefer to position the distal portion of the shunt into the pleural space rather than the cardiac atrium.

A retrospective analysis by McGovern et al found that for normal-pressure hydrocephalus, VAS appeared to be at least as safe as the more commonly used VPS. ^[3]

Contraindications for VAS placement include the following:

• Bacteremia
• CSF infection
• Endocarditis
• History of immune-complex glomerulonephritis (eg, shunt nephritis)
• Prothrombotic state
• Pulmonary hypertension
• Congestive heart failure

Relative contraindications may include a history of pulmonary embolism and systemic anticoagulation.

A retrospective analysis by Rymarczuk et al compared the long-term outcomes and adverse occurrences associated with both VPS and VAS in 544 pediatric patients followed for at least 90 days (VPS, 5.9 y; VAS, 5.3 y). ^[4] Overall survival was superior for VPSs, but if electively scheduled VAS-lengthening procedures were not considered true failures, no significant survival difference was noted. VPSs demonstrated significantly greater survival in patients younger than 7 years but not in older children. VASs had significantly lower rates of infection and proximal failure.

Gmeiner et al retrospectively analyzed long-term outcomes of VAS surgery in 61 pediatric patients with hydrocephalus. ^[5] Primary VAS was the first shunt type in 68.85% of patients; conversions to second-line VAS were carried out the remaining 31.15%. The rates of VAS revision for dysfunction or elective lengthening of a short atrial catheter were 52.2% and 22.9%, respectively. There was no difference in the number of revisions between patients with primary VASs and those with second-line VASs. Specific VAS complications were rarely observed and completely reversible after treatment.