Endovascular Repair of TAA and AAA

Drawn from “Global Dynamics of Surgical and Interventional Cardiovascular Procedures, 2015-2022.”

Abdominal Aortic Aneurysm. During the past two decades, advances in interventional technologies paved the way for the advent of a considerably less invasive and risky endovascular AAA repair procedure. The procedure involves a transcatheter deployment of the specially designed endovascular prosthesis (typically combining sealing functions of the vascular graft and full or partial stenting support structure) into a defective segment of aorta with the goal of excluding the aneurysmal sac from blood circulation.

The endovascular stent-grafts (SGs) – which come both in self-expanding or balloon-expandable versions – are typically anchored to an undamaged part of the aorta both above and below the aneurysm via a compression fit or/and with a special fixation mechanism like hooks, barbs, etc.

To accommodate a great morphological diversity of aortic aneurysms the vast majority of endovascular SGs is employing a modular design concept providing the aorto iliac, bifurcated and straight tubular device configurations to cover a variety of AAA indications. Several SG systems also feature an open stenting structure at proximal end to enable suprarenal device deployment required in about 30% to 35% of all AAA cases warranting intervention.

In its idea, the endovascular repair of abdominal aortic aneurysm was intended to produce clinical outcomes comparable to these yielded by the open surgery, while reducing the associated trauma, recovery time, morbidity and the overall treatment cost. It was also generally expected that availability of less-invasive endovascular treatment option would allow to extend caseloads coverage to sizable rupture-prone AAA patient subsets who are poor surgical candidates.

Thoracic Aortic Aneurysms. Introduced in Europe and the U.S. in 1998 and 2005, accordingly, endovascular techniques for aneurysm (and aortic dissection) repair on thoracic aorta represented a logical extension of the very same basic concept and technology platforms that enabled the development of AAA stent-grafts.

Because of extremely high mortality and morbidity rates associated with TAA surgery, the need for minimally invasive endovascular treatment option was even more compelling than that in AAA case.

Similar to AAA endovascular repair devices, TAA stent-grafts are intended to minimize the risk of catastrophic thoracic aortic aneurysm rupture via effective exclusion (isolation) of the aneurismal sac from blood circulation.

Unlike AAA implants, commercially available TAA stent-grafting devices feature relatively simple tubular unibody architecture with sealing cuffs (or flanges) at proximal and distal end.

Insertion of TAA SGs is done under fluoroscopic guidance via a singular femoral puncture with the use of standard transcatheter techniques. Depending on the aneurysm morphology, one or two overlapping devices might be used to ensure proper aneurismal sac isolation.

The average ICU and hospital stays and post-discharge recovery period for endovascular TAA repair procedure are generally similar to these for AAA stent-grafting intervention.

Although practical clinical experience with endovascular repair of thoracic aortic aneurysm remains somewhat limited, findings from European and U.S. clinical studies with TAA stent-grafting tend to be very encouraging. Based on these findings, stent-grafting of rupture-prone aneurysm on ascending thoracic aorta can be performed with close to perfect technical success rate yielding radical reduction in intraoperative mortality and complications compared to TAA surgery as well as impressive improvement in long-term patient survival.

Similar to AAA endografting, the main problems associated with the use of TAA SG systems include significant incidence of endoleaks and occasional device migration which require reintervention.

Below is illustrated a comparison of the two most significant markets for AAA and TAA repair, the U.S. and Asia/Pacific. Two points are clear: (1) A significant portion of potential treatment caseload in AAA/TAA has yet to be realized, and (2) the U.S. and Asia/Pacific markets operate by different rules.

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