Endovascular aneurysm repair: Predicting late complications from vessel-endograft interactions

Research output: Types of ThesisDoctoral ThesisInternal

Abstract

This thesis aims to increase our understanding on risk factors that affect the durability of EVAR. In particular, how several different baseline morphological characteristics of the aorta and iliac arteries influence EVAR-related complications are investigated. Additionally, the interaction between the implanted endograft and the recipient patients’ vessels, particularly at the seal zones – areas of intimate apposition between the implanted endograft with the proximal neck and iliac arteries - are assessed. Importantly, how the implanted endograft remains positioned and apposed to the vessel wall is determinant for successful and durable AAA exclusion from the pressurized arterial blood and the patient protected from the risk of AAA rupture.
Part I addresses specific preoperative anatomical characteristics of the proximal aneurysm neck. Chapters 1 and 2 highlight the increased risks associated with EVAR when performed in patients with wide (diameter ≥30mm) proximal aortic necks. In Chapter 1, 427 patients treated at three high-volume centers in The Netherlands were included. An infrarenal neck diameter of ≥30 mm was found to be an independent risk factor for neck-related adverse events, type 1A endoleak and neck-related secondary interventions. This study was not a matched case-controlled study, resulting in significantly different groups in respect of endograft oversizing and other neck related characteristics, such as inversed tapered neck configuration and presence of neck thrombus. However, it is a large and consecutive real-world series of patients treated with a contemporary late-generation endograft. Also, adjusted analyses for these baseline differences were provided. Consequently, albeit additional endograft oversizing might mitigate this risk, ultimately, these patients may still experience a greater risk of developing proximal seal-related complications and require additional interventions. Chapter 2 is an international registry-based study including 1257 patients also assessing the impact of wide proximal neck diameter at baseline on outcomes following standard EVAR. As in chapter 1, in adjusted analyses, patients with neck diameter ≥30 mm were at greater risk for development of type 1A endoleaks and suffering post-EVAR AAA rupture. Chapter 3 is the late follow-up of a cohort study initiated with 110 patients.1 In this chapter, aortic neck angulation and its implications on outcomes following standard EVAR at long-term is evaluated. Patients with neck length >15 mm, infrarenal angle (ß) >75º, and/or suprarenal angle (α) >60ºor neck length >10 mm with ß >60º, and/or α >45º were included in the study group and compared with a matched control group. At 7 years postoperatively, freedom from type 1A endoleaks was significantly lower among patients with severely angulated proximal necks. Chapter 4 focuses upon mortality and causes of death following elective EVAR, and searches associations between baseline anatomical characteristics with overall and cardiovascular related mortality. Interestingly, patients with AAA-diameters >70mm were at increased risk of all cause and cardiovascular mortality. Additionally, patients with infrarenal neck-diameters ≥30mm have a greater risk of cardiovascular mortality, which was not AAA-related.
Part II focuses on the interactions between the implanted endograft and the recipient patient. The effects exerted by the endograft on the proximal seal zone within the infrarenal aortic neck are targeted in Chapter 5. Accordingly, following EVAR, dilatation within the infrarenal neck is frequent, with >50% of the patients presenting neck dilatation > 10%. Aortic neck dilatation was found to be associated with baseline neck-diameter while the Excluder endograft had a protective effect. However, only when aortic neck dilatation had surpassed the nominal diameter of the implanted endograft, were associations with type 1A endoleak and endograft-migration >5mm found. In Chapter 6, our attention is drawn towards the distal seal zones, within the iliac arteries. Seldom assessed in EVAR reports, this distal seal environment was found to be dynamic, with vessel enlargement occurring approximately in half of the cases. Endograft iliac limb retrograde migration occurred in 9.1% of the cohort and was associated with iliac seal complications. Distal seal-related adverse events were also associated with larger AAA-diameter. In contrast, Chapter 7 focuses on changes occurring within the luminal surface of the endograft following implantation, in respect of the development of thrombotic deposits. Albeit having been identified among 55% of the studied patients, mural thrombosis within the main body of the endograft was not associated with the occurrence of thromboembolic events up to 5 years. Similarly, mural thrombus within the endografts’ iliac limbs was also found to be clinically uneventful, with treatment being only indicated for those patients who develop a thromboembolic event.
Part III is dedicated to outcomes following EVAR and associated complications. In Chapter 8, the importance of EVAR planning, resorting to an anatomically-tailored endograft selection is stressed. Accordingly, this strategy resulted in comparable results among two different contemporary endografts in patients with significantly distinct baseline anatomies. Chapter 9 underlines the importance of respecting the anatomical boundaries of each endograft defined by their manufactures within the instructions for use (IFU). Noteworthy, although EVAR within IFU is associated with less complications, not all anatomical characteristics enclose per si a greater risk of complications when certain thresholds are surpassed, suggesting that EVAR may be effectively accomplished in some of these outside IFU settings. In Chapter 10, the need for continued clinical and imaging surveillance is analyzed from a risk related point of view. If on one hand, the risk of developing late complications due to endograft dislocation, disconnection, material fatigue or to progressive degeneration of the adjacent vessel segments requires long-term imaging follow-up, on the other ionizing radiation-based imaging albeit adequate to detect many EVAR-related complications carries a risk of stochastic effects from radiation exposure, which may lead to cancer, and may be globally inefficient unless focused on high-risk individuals. Consequently, the adoption of individually tailored protocols may result in a more effective resource allocation, along with minimizing the risks from radiation exposure while providing timely detection of complications.
Original languageEnglish
Awarding Institution
  • Erasmus University Rotterdam
Supervisors/Advisors
  • Verhagen, Hence, Supervisor
  • Stolker, Robert jan, Supervisor
  • Bastos Goncalves, Frederico, Co-supervisor
  • van Rijn, Marie Josee, Co-supervisor
Award date22 Nov 2023
Place of PublicationRotterdam
Print ISBNs978 – 94 – 6361 – 904 - 2
Publication statusPublished - 22 Nov 2023

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