Endovascular Transcarotid Artery Revascularization Using the Walrus Balloon Guide Catheter: Preliminary Experience

BACKGROUND

The Walrus Balloon Guided System Catheter is a new generation of balloon guide catheter (BGC) designed to bypass some technical limitations of conventional BGC devices. Their utility in cervical carotid disease treatment has not been reported. We report our preliminary experience in cervical carotid treatment using the Walrus BGC to perform a modified endovascular transcarotid artery revascularization technique.

METHODS

Patients with cervical carotid disease undergoing endovascular treatment using the Walrus BGC at our institution were identified. The pertinent baseline demographics and procedural outcomes were collected and analyzed.

RESULTS

Twelve patients were included (median age, 70; 58.3% females). All patients had an imaging-confirmed cervical carotid disease that indicated intervention: 6 with high-grade cervical arteriosclerotic carotid stenosis, 2 with intraluminal thrombi, 1 with traumatic carotid dissection, and 3 patients with cervical carotid tandem occlusion along with acute ischemic stroke secondary to large vessel occlusion that required mechanical thrombectomy. Carotid artery stenting was performed in all cases, except 2 of the 3 mechanical thrombectomy cases (angioplasty only). All patients had at least periprocedural follow-up of 30 days, with no stroke, myocardial infarction, or death encountered.

CONCLUSIONS

We describe a modified endovascular transcarotid artery revascularization technique. We used a standard femoral access to navigate the Walrus catheter in the common carotid artery, followed by balloon inflation for proximal flow arrest or flow reversal (when connected to the aspiration pump) to deploy the carotid stent across the stenosis, while avoiding distal external carotid artery balloon occlusion. Successful treatment was achieved in all cases, with no periprocedural complications encountered.

Subsurface swimming and stationary diving are metabolically cheap in adult Pacific walruses (Odobenus rosmarus divergens)

Walruses rely on sea-ice to efficiently forage and rest between diving bouts while maintaining proximity to prime foraging habitat. Recent declines in summer sea ice have resulted in walruses hauling out on land where they have to travel farther to access productive benthic habitat while potentially increasing energetic costs. Despite the need to better understand the impact of sea ice loss on energy expenditure, knowledge about metabolic demands of specific behaviours in walruses is scarce. In the present study, 3 adult female Pacific walruses (Odobenus rosmarus divergens) participated in flow-through respirometry trials to measure metabolic rates while floating inactive at the water surface during a minimum of 5 min, during a 180-second stationary dive, and while swimming horizontally underwater for ∼90 m. Metabolic rates during stationary dives (3.82±0.56 l O2 min-1) were lower than those measured at the water surface (4.64±1.04 l O2 min-1), which did not differ from rates measured during subsurface swimming (4.91±0.77 l O2 min-1). Thus, neither stationary diving nor subsurface swimming resulted in metabolic rates above those exhibited by walruses at the water surface. These results suggest that walruses minimize their energetic investment during underwater behaviours as reported for other marine mammals. Although environmental factors experienced by free-ranging walruses (e.g., winds or currents) likely affect metabolic rates, our results provide important information for understanding how behavioural changes affect energetic costs and can be used to improve bioenergetics models aimed at predicting the metabolic consequences of climate change on walruses.

Novel herpesvirus discovered in walrus liver

A walrus (Odobenus rosmarus) born in an aquarium and hand-reared in Japan died at the age of 11 months. The affected animal showed fever and anorexia and had high levels of AST and ALT. Necropsy showed multiple necroses in the liver and adrenal glands and histological examination revealed necrotic lesions of the liver and adrenal cortex, both of which contained intranuclear inclusions. Electron microscopic analysis of the liver sample showed herpesvirus-like particles. High-throughput sequencing analysis of the liver sample and phylogenetic analysis of herpesvirus polymerase genes identified a new virus, Walrus alphaherpesvirus 1 (WaHV-1), which belonged to the subfamily Alphaherpesvirinae and had high homology with Phocid alphaherpesvirus 1. Phylogenetic analysis of the UL30 gene encoding glycoprotein B revealed that WaHV-1 was closely related to a cluster of phocid herpesviruses, including one that caused high mortality rates in harbor seals during past outbreaks. The mother walrus of the dead animal showed evidence of herpesvirus infection in the past and potentially harbored WaHV-1. As a result of hand-rearing, the dead animal might have acquired WaHV-1 from its infected mother and succumbed to WaHV-1 due to lack of maternal IgG, including those that could neutralize WaHV-1.

A new tuskless walrus from the Miocene of Orange County, California, with comments on the diversity and taxonomy of odobenids

We describe Titanotaria orangensis (gen. et. sp. nov.), a new species of walrus (odobenid) from the upper Miocene Oso Member of the Capistrano Formation of Orange County, California. This species is important because: (1) It is one of the best-known and latest-surviving tuskless walruses; (2) It raises the number of reported odobenid taxa from the Oso Member to four species making it one of the richest walrus assemblages known (along with the basal Purisima of Northern California); (3) It is just the second record of a tuskless walrus from the same unit as a tusked taxon. Our phylogenetic analysis places T. orangensis as sister to a clade that includes Imagotaria downsi, Pontolis magnus, Dusignathus spp., Gomphotaria pugnax, and Odobeninae. We propose new branch-based phylogenetic definitions for Odobenidae, Odobeninae, and a new node-based name (Neodobenia) for the clade that includes Dusignathus spp., G. pugnax, and Odobeninae. A richness analysis at the 0.1 Ma level that incorporates stratigraphic uncertainty and ghost lineages demonstrates maximum peaks of richness (up to eight or nine coeval lineages) near the base of Odobenidae, Neodobenia, and Odobenini. A more conservative minimum curve demonstrates that standing richness may have been much lower than the maximum lineage richness estimates that are biased by stratigraphic uncertainty. Overall the odobenid fossil record is uneven, with large time slices of the record missing on either side of the Pacific Ocean at some times and biases from the preserved depositional environments at other times. We recognize a provisional timescale for the transition of East Pacific odobenid assemblages that include "basal odobenids" (stem neodobenians) from the Empire and older formations (>7 Ma), to a mixture of basal odobenids and neodobenians from the Capistrano and basal Purisima (7-5 Ma), and then just neodobenians from all younger units (<5 Ma). The large amount of undescribed material will add new taxa and range extensions for existing taxa, which will likely change some of the patterns we describe.

A colostrum trypsin inhibitor gene expressed in the Cape fur seal mammary gland during lactation

The colostrum trypsin inhibitor (CTI) gene and transcript were cloned from the Cape fur seal mammary gland and CTI identified by in silico analysis of the Pacific walrus and polar bear genomes (Order Carnivora), and in marine and terrestrial mammals of the Orders Cetartiodactyla (yak, whales, camel) and Perissodactyla (white rhinoceros). Unexpectedly, Weddell seal CTI was predicted to be a pseudogene. Cape fur seal CTI was expressed in the mammary gland of a pregnant multiparous seal, but not in a seal in its first pregnancy. While bovine CTI is expressed for 24-48 h postpartum (pp) and secreted in colostrum only, Cape fur seal CTI was detected for at least 2-3 months pp while the mother was suckling its young on-shore. Furthermore, CTI was expressed in the mammary gland of only one of the lactating seals that was foraging at-sea. The expression of β-casein (CSN2) and β-lactoglobulin II (LGB2), but not CTI in the second lactating seal foraging at-sea suggested that CTI may be intermittently expressed during lactation. Cape fur seal and walrus CTI encode putative small, secreted, N-glycosylated proteins with a single Kunitz/bovine pancreatic trypsin inhibitor (BPTI) domain indicative of serine protease inhibition. Mature Cape fur seal CTI shares 92% sequence identity with Pacific walrus CTI, but only 35% identity with BPTI. Structural homology modelling of Cape fur seal CTI and Pacific walrus trypsin based on the model of the second Kunitz domain of human tissue factor pathway inhibitor (TFPI) and porcine trypsin (Protein Data Bank: 1TFX) confirmed that CTI inhibits trypsin in a canonical fashion. Therefore, pinniped CTI may be critical for preventing the proteolytic degradation of immunoglobulins that are passively transferred from mother to young via colostrum and milk.