Endovascular embolization of canine hepatic arteriovenous malformations using precipitating hydrophobic injectable liquid (PHIL) liquid embolic agent: a proof of concept study

Abstract

Background: Hepatic arteriovenous malformations (HAVMs) are rare congenital lesions consisting of multiple highpressure arteries feeding into low-pressure veins via a central nidus. Massive haemorrhage, portal hypertension and hepatic insufficiency can ensue. Endovascular embolization is increasingly a first line treatment method although there is no general consensus or guidelines on the most effective embolic agent or approach. We describe the novel treatment of two dogs with congenital hepatic AVMs using a modified version of the 'pressure cooker' technique often utilised in neurointervention with the DMSO-based PHIL embolic agent delivered via the DMSO compatible Scepter-XC dual lumen balloon catheter. Case presentation: Two paediatric dogs were diagnosed with hepatic AVMs. Both dogs presented with ascites and abnormal liver function tests. CT angiograms revealed hepatic arterio-portal malformations arising from an enlarged celiac artery. Selective catheterisation of the artery supplying the AVM was achieved via a femoral artery approach. A Scepter XC dual-lumen compliant balloon microcatheter and Traxcess 0.014 guidewire combination was advanced to the nidus via through the 5Fr guide catheter towards the nidus. Inflation of the balloon occluded arterial inflow and PHIL was injected under continuous fluoroscopic screening until the PHIL embolic agent penetrated into the draining portal vein beyond the nidus. In patient 1, normal portal venous waveform was restored with reversal of severe hepatic insufficiency. Whilst there was initial improvement post-operatively in patient 2 with normalisation of portal vein pressures and flow, opening of collateral nidus vessels re-established the high-pressure communication, and euthanasia was elected by the owner. Conclusions: The 'pressure cooker' technique is a safe and efficacious approach to the treatment of canine HAVMs. The novel use of PHIL and the Scepter XC balloon catheter has several advantages over conventional endovascular approaches. Translational application to human paediatric interventions for similar conditions where embolic and contrast agent volume constraints are similar can be considered.

Ethylene vinyl alcohol copolymer to treat an intracranial arteriovenous malformation in a dog

“…5,15 In these reports, treatment with EVOH was well tolerated. 5,15 Limitations of this technique and report should be recognized. This procedure is very challenging technically, and a strong understanding of anatomy and endovascular instrumentation is essential.…”

“…When embolization is pursued, liquid embolic agents including cyanoacrylate and ethylene vinyl alcohol generally are chosen, but particles and coils also can be considered 5,15 . Before the last 20 years, cyanoacrylate (particularly n ‐butyl cyanoacrylate) was the embolic liquid of choice.…”

“…This ability to control the distribution of the embolic agent and rate of polymerization is highly advantageous, especially when treating AVMs in highly challenging locations such as deep in the brain. In companion animals, descriptions of the use of EVOH to treat AVMs have included a peripheral AVM of a hind limb and hepatic AVMs in dogs 5,15 . In these reports, treatment with EVOH was well tolerated 5,15 …”

“…14 When embolization is pursued, liquid embolic agents including cyanoacrylate and ethylene vinyl alcohol generally are chosen, but particles and coils also can be considered. 5,15 Before the last 20 years, cyanoacrylate (particularly n-butyl cyanoacrylate) was the embolic liquid of choice. Cyanoacrylate polymerizes upon contact with blood, and this embolic agent is challenging to use because polymerization occurs quickly and unpredictably.…”

“…The most common location for AVMs is the liver, and both surgical and endovascular techniques have been described for treatment. [3][4][5][6] A naturally occurring intracranial AVM has not been reported previously in dogs, to our knowledge, but an AVM in the spinal cord and an arteriovenous fistula of the temporal branches of the external carotid artery have been reported in single case reports. 7,8 In the dog of our report, most clinical signs occurred likely secondary to the space-occupying effect of the additional abnormal blood vessels of the AVM.…”