In the developed world, extreme prematurity is the leading cause of neonatal mortality and morbidity due to a combination of organ immaturity and iatrogenic injury. Until now, efforts to extend gestation using extracorporeal systems have achieved limited success. Here we report the development of a system that incorporates a pumpless oxygenator circuit connected to the fetus of a lamb via an umbilical cord interface that is maintained within a closed ‘amniotic fluid' circuit that closely reproduces the environment of the womb. We show that fetal lambs that are developmentally equivalent to the extreme premature human infant can be physiologically supported in this extra-uterine device for up to 4 weeks. Lambs on support maintain stable haemodynamics, have normal blood gas and oxygenation parameters and maintain patency of the fetal circulation. With appropriate nutritional support, lambs on the system demonstrate normal somatic growth, lung maturation and brain growth and myelination.

Objectives: Very few studies have addressed the clinical significance of ‘bovine’ aortic arch (BA). We sought to determine whether BA is associated with thoracic aortic disease, including thoracic aortic aneurysm, aortic dissection, aortic rupture, and accelerated aortic growth rate. Methods: We retrospectively reviewed CT and/or MRI scans of 612 patients with thoracic aortic disease and 844 patients without thoracic aortic disease to determine BA prevalence. In patients with thoracic aortic disease, we reviewed hospital records to determine growth rate, prevalence of dissection and rupture, and accuracy of radiology reports in citing BA. Results: 26.3% of the patients with thoracic aortic disease had concomitant BA, compared to 16.4% of the patients without thoracic aortic disease (p < 0.001). There was no association between BA and prevalence of dissection or rupture (p = 0.38 and p = 0.56, respectively). The aortic expansion rate was 0.29 cm/year in the BA group and 0.09 cm/year in the non-BA group (p = 0.004). Radiology reports cited BA in only 16.1% of the affected patients. Conclusions: (1) BA is significantly more common in patients with thoracic aortic disease than in the general population. (2) Aortas expand more rapidly in the setting of BA. (3) Radiology reports often overlook BA. (4) BA should not be considered a ‘normal’ anatomic variant.

EXTEND (EXTra-uterine Environment for Neonatal Development) is a novel system that promotes physiological development by maintaining the premature lamb in a sterile fluid environment and providing gas exchange via a pumpless arteriovenous oxygenator circuit. During the development of EXTEND, different cannulation strategies evolved with the aim of improving circuit flow. The present study examines how different cannulation strategies affect EXTEND circuit haemodynamics in extreme premature lambs. Seventeen premature lambs were cannulated at gestational ages 105-117 days (term 145-150 days) and supported on EXTEND for up to 4 weeks. Experimental groups were distinguished by cannulation strategy: carotid artery outflow and jugular vein inflow (CA/JV; n = 4), carotid artery outflow and umbilical vein inflow (CA/UV; n = 5) and double umbilical artery outflow and umbilical vein inflow (UA/UV; n = 8). Circuit flows and pressures were measured continuously. As we transitioned from CA/JV to CA/UV to UA/UV cannulation, mean duration of circuit run and weight-adjusted circuit flows increased (P < 0.001) and the frequency of flow interruptions declined (P < 0.05). Umbilical vessels generally accommodated larger-bore cannulas, and cannula calibre was directly correlated with circuit pressures and indirectly correlated with flow:pressure ratio (a measure of post-membrane resistance). We conclude that UA/UV cannulation in fetal lambs on EXTEND optimizes circuit flow dynamics and flow stability and also supports circuit flows that closely approximate normal placental flow.

Recent studies have confirmed a close association between various medical conditions (intracranial aneurysm, abdominal aortic aneurysm, temporal arteritis, autoimmune disorder, renal cysts), certain aortic anatomic variants (bovine aortic arch, direct origin of left vertebral artery from aortic arch, bicuspid aortic valve), and family history of aneurysm disease with thoracic aortic aneurysm and dissection. This paper reviews these associations. We propose to capitalise on these associations as powerful and expanding opportunities to diagnose the virulent but silent disease of thoracic aortic aneurysm. This can be accomplished by recognition of this ‘guilt by association’ with the other conditions. Thus, patients with associated diseases and anatomic variants should be investigated for silent aortic aneurysms. Such a paradigm holds substantial potential for reducing death from the silent killer represented by thoracic aortic aneurysm disease.

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