BioEngineering Research Group

Thoracoabdominal aortic aneurysm

To Develop An Advanced Patient Specific Computational Test-bed for the Evaluation Of Aortic Endografts In The Treatment Of TAAAs

Jamie Concannon

Thoracic Aortic Aneurysms (TAAs) although less common than Abdominal Aortic Aneurysms (AAAs) are believed to rupture more frequently, with 95% of patients asymptomatic until the catastrophic point of rupture. With an associated mortality rate following aortic rupture of over 90%, aneurysms affecting the ThoracoAbdominal Aorta therefore, present a daunting challenge to vascular surgeons and interventionalists worldwide in optimizing treatment for these unpredictable aneurysms.

Currently the threshold for intervention for such aneurysms rests at a diameter of 5.5 cm orthogonal to the aortic centerline, however this threshold has been generated from investigations into the rupture risk of AAAs and does not account for the innate biomechanical differences between the thoracic and abdominal aorta. Investigation into the tissue biomechanics of ThoracoAbdominal Aortic Aneurysms (TAAAs) will allow for a greater understanding of localized disease progression and subsequently more accurate timing of surgical interventions.

For more information on this research project, contact Jamie Concannon.

Stanford Type B aortic dissection

Biomechanics of aortic dissection

Brian FitzGibbon

Aortic Dissection (AD) occurs due to intimal injury which causes an initial separation of the arterial layers. The separation is thought to occur most commonly between the intima and media. This intima-medial tear is the pre-cursor for crack propagation, which is thought to occur between the lamellar elastic layers of the media. The propagation of this crack/buckle commonly results in the development of pathological blood flow between the medial layers. This blood flow exerts an internal intra- media pressure which not only causes further separation of the layers, but also expansion of this pathological conduit known as the “False lumen”. This is often problematic as it results in a reduction in blood flow to the major arteries which stem from the aorta; the celiac, the superior mesenteric (SMA), the renals, the inferior mesenteric (IMA), the intercostal, and the spinal arteries. If these arteries are occluded/malperfused the outcome for the patient can be catastrophic (paraplegia, renal failure, stroke, etc.). 

For more information on this research project, contact Brian FitzGibbon.

Aortic arch Aneursym

Experimental Investigation of Patient Specific Complex Aortic Arch Aneurysms Treated with the Cardiatis Multilayer Flow Modulator

Ala Elhelali

Aortic arch aneurysms are rare diseases occurring in 10 cases per 100,000 patients per year. These aneurysms are typically detected at large diameters, and patients presenting with aortic arch aneurysms often have multiple co-morbidities or particular anatomical configurations. This leaves them unsuitable for open repair, hybrid repair or thoracic endovascular (TEVAR) stent graft (SG) repair. One option for these high-surgical risk patients is the Cardiatis Multilayer Flow Modulator (MFM®). It is bare metal stent permits coverage of the supra-aortic branch vessels without compromising perfusion to these vessels. It provides a new conduit for blood and diverts blood away from the aneurysm wall thereby shielding it from localised pressures. After implantation of the MFM® device, the aneurysm may shrink, grow, or stabilise in diameter. In some cases, graft failure through kinking or loss of seal at the proximal or distal ends may occur. Little work has been conducted on examining the effect of the MFM® device failures on aneurysm haemodynamics.

This thesis aimed to investigate the performance of the MFM® device in treating complex aortic arch aneurysms. Device performance was tested by analysing clinical data, geometrical data and assessing the hemodynamics in untreated and treated aortic arch aneurysms. A better understanding of treated complex aortic arch aneurysms using the MFM® device will provide insight into how to improve and modify treatment techniques and improve device design to facilitate safer and more effective treatment outcomes. Experimental in vitro patient-specific compliant thin walled models provide a means to investigate the hemodynamic effects of the MFM® device in these complex pathologies.

For more information on this research project, contact Ala Elhelali