The use of SMI in surveillance of endovascular aneurysm repair (EVAR)

Introduction: Endovascular aneurism repair (EVAR) is the treatment of choice in the repair of abdominal aortic aneurysms. Re-intervention rate is higher for EVAR patients compared with open repair requiring lifelong surveillance. This usually consists of a combination of computed tomography angiography (CTA), colour Doppler ultrasound (CDUS) and plain projection radiography. Due to high cumulative radiation dose and nephrotoxicity of CTA and the poor sensitivity of CDUS, other imaging strategies have been proposed. This study reports the use of a new imaging modality (SMI) for the surveillance of EVAR.

Methods: A retrospective audit was conducted comparing endoleak detection rates with CTA and US (CDUS and SMI) over a 2 year period. A standard scanning protocol was adopted where the presence of endoleaks and the maximum diameter of the aneurysm sac were reported for CDUS, SMI and contemporaneous CTA scans.

Results: Of the 195 EVARs scanned, 25 demonstrated an endoleak on SMI (13%) and 13 demonstrated an endoleak on CDUS (7%). Therefore SMI detected almost twice as many endoleaks (similar to literature results when comparing contrast enhanced ultrasound (CEUS) to CDUS). As a comparison of SMI with CTA, 49/195 patients had a contemporaneous CTA. 34 demonstrated no endoleak on SMI and 33 demonstrated no endoleak on CTA (US failing to detect 1 endoleak). Of the 15 SMI demonstrated endoleaks only 9 were visible on CTA (60% failure) and of the 6 undetected, at least 2 patients had expanding sac sizes (indication of late aneurysm rupture).

Conclusion: SMI was demonstrated to be an effective and safe tool for endoleak detection. SMI surpassed CDUS in sensitivity and in some circumstances outperformed CTA where literature outlines similarity of SMI with CEUS. This has led to a change in our local surveillance protocol (replacing 1 and 6 month follow-up CTA scans with SMI).