From the Guidelines
Arteriovenous (AV) shunt data should be monitored using Doppler ultrasound (US) as the primary screening tool, with follow-up suggested 6-monthly, and venography with pressure measurements as the gold standard for confirming shunt dysfunction. The details regarding AV shunt data involve assessing shunt function to identify either insufficient shunting or excessive shunting, which can lead to complications such as early severe liver failure, chronic encephalopathy, or cardiac failure refractory to medical therapy 1.
Key Parameters for Shunt Dysfunction
When evaluating shunt function, several key parameters are used during Doppler US surveillance, including:
- Shunt velocity: 90–200 cm/s
- Portal vein velocity: ~30 cm/s
- Phasic waveform
- Hepatofugal flow in portal vein branches directed towards the shunt Suspicion of shunt dysfunction is raised when there is colour Doppler aliasing at the stenosis site, velocity >200 cm/s at the level of stenosis, or velocity <90 cm/s at the non-stenotic segment, among other signs 1.
Diagnosis and Follow-Up
Diagnosis of shunt dysfunction is crucial, and Doppler US is preferred over systematic venography due to its non-invasive nature, wide availability, and lack of ionizing radiation. However, it is essential to be aware of the weak performance of Doppler in detecting an increase in the porto-caval gradient 1. Venography with pressure measurements is used when suspicion arises based on Doppler results or in cases of recurrence of PHT-related complications, with a gradient ≥12 mmHg indicating shunt dysfunction.
Clinical Implications
Monitoring AV shunt data is critical in managing patients with shunts, as it helps clinicians identify potential complications early and intervene accordingly. Reduction of the shunt is recommended in cases of early severe liver failure, chronic encephalopathy, or cardiac failure refractory to medical therapy, although no particular technique can be recommended for the shunt reduction 1.
From the Research
Arteriovenous (AV) Shunt Data
There are no research papers to assist in answering this question as the provided studies focus on ventriculoperitoneal shunts, not arteriovenous shunts.
Related Shunt Data
However, the following information is available regarding shunt data in general:
- A study published in 2018 2 found that education regarding the care of patients with shunts by providing written cards with shunt type/setting and access to reference materials seems to be effective.
- A 1994 study 3 analyzed data from 95 adult patients treated with ventriculoperitoneal shunts and found that the choice of shunt type, the perioperative use of antibiotics, and the degree of surgical emergency were not correlated with complication or failure rates.
- A 2011 study 4 found that bradycardia without associated hypertension is a common sign of ventriculo-peritoneal shunt malfunction in children.
- A 2008 study 5 found that poor flow of CSF on shunt tap is highly predictive of obstruction of the proximal catheter.
- A 2019 study 6 presented the analysis and the rates of complications progressively occurring during the first year after shunt surgery in patients with idiopathic normal pressure hydrocephalus, finding that 26% of patients experienced symptoms due to shunt underdrainage and 9% experienced symptomatic overdrainage.
Key Findings
Some key findings from the studies include:
- The importance of education and access to reference materials for caregivers of patients with shunts 2
- The need for careful opening pressure setting and rigorous follow-up to reduce complications 6
- The predictive value of bradycardia and shunt tap results for shunt malfunction 4, 5
- The rates of complications and shunt malfunction in different patient populations 3, 6