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Application Of Sac Pressure Measurement As A Surveillance Tool Following EVAR

David H Stone, Michael J Stirling, Cynthia K Shortell, Jeffrey Lawson, Rebecca Petersen, Richard L McCann.
Duke University Medical Center, Durham, NC.

OBJECTIVES: Endovascular aneurysm repair (EVAR) has emerged as the preferred treatment for abdominal aortic aneurysm (AAA). The ideal method of follow-up remains controversial: the significance of the presence or absence of an endoleak is unknown. The pressure within the residual sac is an appealing method of evaluating persistent endoleak, as it is a physiologic, rather than radiographic measurement. Also appealing are the lower cost, and patient convenience. In this study, we investigate the CaridoMEMS® device as a surveillance tool in this setting.

METHODS: The records of 50 patients undergoing EVAR with CardioMEMS® implantation from April 2006 to November 2006 were reviewed. Intraoperative sac pressure measurements were obtained and compared before AAA exclusion, immediately after exclusion, following ballooning, one month postoperatively. Sac pressure was correlated with CT findings and compared among patients receiving two different commercially available endografts.

RESULTS: Fifty patients(mean age 74 years; 43 male(86%) underwent EVAR with CaridoMEMS® implantation. Mean sac pressure before AAA exclusion decreased after deployment(1.02±0.23 vs 0.63±0.31, P=NS). There was a significant decrease in sac pressure following intraoperative balloon insufflation(0.36±0.24, P<0.001). In 8 patients(16%) with documented endoleaks on completion angiography, there was no statistical correlation with sac pressure both pre and post-ballooning(0.65±0.36 vs 0.28±0.18, P=.213). Sac pressure did not correlate in 8(16%) patients with CT documented endoleaks at POD 30 compared to those without leak(0.12±0.08 vs 0.21±0.14, P=0.098). Unexpectedly, pressure measurements were significantly lower in patients treated with the Gore Excluder(n=24) compared to the Cook Zenith(n=24) endograft at POD 30(0.13±0.11 vs 0.26±0.14, P<0.007).

CONCLUSIONS: Sac pressure measurements consistently decrease following intraoperative balloon insufflation, but do not correlate with radiographic endoleak. These data suggest that sac pressure may effectively differentiate endoleaks with physiologic significance. Presently, these findings support the practice of continued postoperative CT surveillance. The significance of discordant pressure recordings between endograft types remains uncertain.