2007 Abstracts: Efficacy of Sac Pressure Monitor in EVAR

Background: Endovascular repair (EVAR) of abdominal aortic aneurysm (AAA) has gained acceptance since its introduction in 1991. All currently available endograft systems employ self expanding stent designs. All manufacturers, however, recommend that seal zones and overlap zones for modular systems be treated with a compliant molding balloon after deployment. Efficacy of the molding balloon treatment has not been demonstrated. Recently a sac pressure monitor (CardioMEMS®) has become available and we hypothesized that this device will be a useful tool in confirming aneurysm exclusion and assessment of the efficacy of molding balloon treatment of stent grafts for AAA.
Methods: A prospective accumulation of 22 consecutive patients treated at our center with EVAR over a 5 month period (April-August 2006) was undertaken. Patients undergoing EVAR by one surgeon using either the Gore Excluder or the Cook Zenith system had a CardioMEMS® device inserted at the time of EVAR. Sac pressure measurements were obtained intra-operatively prior to aneurysm exclusion, following exclusion, and after molding balloon treatment of the seal zones and overlap zones using either a Cook Coda Balloon or Boston Scientific Equalizer Balloon. Measurements were also obtained on post operative day 1 and at one month post operatively in most patients. Pulse pressure ratios compared to radial arterial line measurements were utilized for the analysis.
Results: Pulse pressure ratios are listed in the table.

The determination of stent graft device was at the discretion of the surgeon. All patients were male. Mean sac pulse pressure ratio before stent graft deployment was 1.07 compared to radial artery pulse pressure, confirming accuracy of the calibrated pressure transducer. Pulse pressure following aneurysm exclusion fell to a mean of 0.67 and fell further after molding balloon treatment to 0.47 (P <.01, paired t test). In no patient with a significant pressure drop was a type 1 endoleak identified. Four patients had little or no drop in sac pressure and were treated intra-operatively with additional balloon inflation with compliant or non compliant balloons. In three patients this resulted in a significant pressure drop. The remaining patient had a small proximal type 1 endoleak which resolved at one month, at which time the pulse pressure ratio fell to .54.
Conclusion: Sac pressure monitoring is a useful adjunct to confirm adequate aneurysm exclusion during EVAR and confirms efficacy of the practice of molding balloon treatment following stent graft deployment. Longer term follow-up will be required to assess utility of the sac pressure sensor for late surveillance. This technology has the potential to significantly change the way EVAR patients are treated and followed and should be studied further.