Wall Motion in Unsupported Endografts: Evidence of Aneurysm Sac Pressurization?

1. Wall Motion in Unsupported Endografts: Evidence of Aneurysm Sac Pressurization? Kathleen Carter, BSN, RN, RVT, FSVT Technical Director Vascular Laboratory Norfolk Surgical Group, Vascular Surgery Div. Clinical Instructor, Department of Surgery, Eastern Virginia Medical School, Norfolk, Virginia

2. Introduction Goals of aneurysm repair: Prevention of aneurysm rupture Maintenance of flow to the distal arterial tree Endovascular repair commonly complicated by endoleak, exposing patient to risk of expansion and rupture Reported in 2.4 to 44% of endovascular repairs

3. Endoleak • Definition: Flow outside of endograft, but within the residual aneurysm sac • Exposes the aneurysm to continued hemodynamic stress and, therefore, risk of rupture • Most commonly from residual branch vessels within the aneurysm (Type II)

4. Endoleak • Effect of endoleak on aneurysm wall morphology is ill defined • Understanding of the hemodynamic characteristics of endoleak is limited • Controversy continues concerning the pressure generated by endoleaks

5. Introduction • Early natural history data shows that despite the presence of endoleak, many aneurysms shrink over time (nonsupported) • Branch-vessel endoleaks were previously thought to have sub-normal pressures • Recent reports suggest endoleaks have near-systemic pressures @ interventional diagnostic pressure sampling.

6. Endoleak • Endoleaks expose the residual aneurysm sac to arterial flow • Potential for aneurysm expansion and possible rupture • Incomplete exclusion of flow in the aneurysm sac may re-pressurize to near systemic pressure

7. Identification of Endoleak • Computed Tomography (CT) • Color Duplex Ultrasound (CDU)

8. Valuable, reliable tool for post operative surveillance of endografts when proper protocol is followed Much more complex, detailed exam than standard aortic ultrasound May be more sensitive to endoleak than CT or even angiography Color Duplex Evaluation of Aortic Endografts

9. Color Duplex Ultrasound for Endoleak

10. Endoleak • Be aware of “clues” 1. B-mode -? Endoleak • low echogenicity • wall motion (nonsupported) • Increasing AAA size

15. This center is currently studying the: Relationship between endoleak location Hemodynamic forces generated by the endoleak on the graft Subsequent graft wall motion

16. If AAA is “re- pressurized”- why do they often shrink in the presence of leak? Endoleaks may cause an asymmetrical deformational force within the aneurysm sac as evidenced by asymmetrical compression of the unsupported endograft = wall motion

17. If there was global “re-pressurization” and systemic pressure throughout the AAA sac Unlikely that AAA size would decrease

18. Two separate photographic pictures obtained during full expansion and full compression of the graft along the axis defined by the endoleak location

19. The graft wall closest to the endoleak (along the axial plain) demonstrates the most compression

21. Guidant (EVT) Ancure Trials Began in 1991 Mandated imaging “core lab” for independent imaging interpretation and correlation On-going independent classification of all imaging data Mean followup in core lab database between three and four years

22. Core Lab data • Review of ultrasound data in 2000 • 412 studies on 124 pts @ 17 sites • 30/124 had notation of wall motion made by ultrasound • All 30 had endoleak at some time point by some modality (CT or CDU)

23. Conclusion • Effect of the force generated by the pressure and flow contained within the endoleak channel causes the endograft wall to be compressed in the area of the endoleak in some portion of the cardiac cycle

24. Conclusion • Forces applied within the aneurysm sac are not uniform • Systemic pressures from endoleaks found within the aneurysm sac appears to be localized to the area of endoleak

25. Vascular & Transplant Specialists Norfolk, Virginia Eastern Virginia Medical School Division of Vascular Surgery