DESCRIPTION
The goal of abdominal aortic aneurysm (AAA) repair is to reduce pressure in the aneurysm sac and thus prevent rupture. Failure to completely exclude the aneurysm from the systemic circulation results in continued pressurization. An endoleak (persistent perfusion of the aneurysmal sac) may be primary (within the first 30 days) or secondary (after 30 days). Endoleaks are reported to vary from 10% - 50% of cases, and there are five types of endoleaks.
Type I endoleaks result from ineffective fixation at either end of the graft; while these can seal spontaneously, risk of rupture is high and intervention is often indicated.
Type II endoleaks result from retrograde filling of the aneurysm mainly from lumbar and/or inferior mesenteric arteries. Risk of rupture is less than with types I and III and type II endoleaks can often be monitored when the aneurysm is shrinking.
Type III endoleaks are caused by failure of the implanted graft and include development of holes, which need to be treated aggressively.
Type IV endoleaks are caused by the porosity of the graft fabric.
Type V endoleaks are referred to as endotension and correspond to continued aneurysm expansion in the absence of a confirmed endoleak.
Endoleaks, particularly types I and III, lead to continued sac pressurization and therefore may be considered technical failures of endovascular aneurysm repair (EVAR). The completeness of exclusion or absence of endoleaks is evaluated by intraoperative angiography. However, interpretation of images can be problematic and it can also cause patient morbidity due to the dye load from repeated injections of contrast material. Direct measurement of sac pressure provides a physiologic assessment of success. Studies have used direct sac pressure measurements with a catheter; the drawback of this approach is the interference by the catheter during endovascular repair and the inability to leave it in place. Since endoleaks may also develop subsequent to the time of surgery, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound are used in monitoring the aneurysmal sac. Percutaneous catheter-based approaches can also be used to measure intrasac pressures postoperatively.
Several factors determine aneurysm sac pressure after EVAR. These include graft-related factors such as endoleak, graft porosity, and graft compliance and anatomic factors such as patency of aneurysm side branches, aneurysm morphology, and the characteristics of aneurysm thrombus.
Given this situation, wireless implantable pressure-sensing devices are being evaluated to monitor pressure in the aneurysm sac. These implanted devices use various mechanisms to wirelessly transmit pressure readings to devices for measuring and recording pressure. These devices have the potential to improve outcomes for patients who have had endovascular repair. They may change the need for or the frequency of monitoring of the aneurysm sac using contrast-enhanced CT scans. They may improve postoperative monitoring. However, the accuracy of these devices must be determined, and potential benefits and risks must be considered and evaluated. At present, two types of systems are being evaluated: radiofrequency or ultrasound-based systems, (e.g., the CardioMEMS EndoSure™ system which is a radiofrequency-based sensor and the ImPressure™ system which is an ultrasound-based sensor).
POLICY
The use of wireless pressure sensors in the intraoperative and/or postoperative management of patients having endovascular aneurysm repair is considered investigational.
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ADDITIONAL INFORMATION
The available research is insufficient regarding improved clinical outcomes, accuracy with the various types of endoleaks, performance over time, the type and number of devices needed, and what long-term complications may develop.
SOURCES
BlueCross BlueShield Association. Medical Policy Reference Manual. (10:2010). Wireless Pressure Sensors in Endovascular Aneurysm (7.01.111). Retrieved September 22, 2011 from BlueWeb. (9 articles and/or guidelines reviewed)
Hinnen, J. W., Koning, O. H., van Bockel, J. H., & Hamming, J. F. (2007). Aneurysm sac pressure after EVAR: The role of endoleak. European Journal of Vascular and Endovascular Surgery, 34 (4), 432-441. (Level 2 Evidence)
Hoppe, H., Segall, J. A., Liem, T. K., Landry, G. J., & Kaufman, J. A. (2008). Aortic aneurysm sac pressure measurements after endovascular repair using an implantable remote sensor: Initial experience and short-term follow-up. European Radiology, 18 (5), 957-965. (Level 3 Evidence - Independent study)
Ohki, T., Ouriel, K., Silveira, P. G., Katzen, B., White, R., Criado, F., et al. (2007). Initial results of wireless pressure sensing for endovascular aneurysm repair: The APEX Trial - acute pressure measurement to confirm aneurysm sac Exclusion. Journal of Vascular Surgery, 45 (2), 236-242. (Level 1 Evidence - Industry sponsored)
Parsa, C. J., Daneshmand, M. A., Lima, B., Balsara, K., McCann, R. L., & Hughes, G. C. (2010). Utility of remote wireless pressure sensing for endovascular leak detection after endovascular thoracic aneurysm repair. Annals of Thoracic Surgery, 89, 446-452. (Level 2 Evidence)
Silveira, P. G., Miller, C.W., Mendes, R. F., & Galego, G. N. (2008). Correlation between intrasac pressure measurements of a pressure sensor and an angiographic catheter during endovascular repair of abdominal aortic aneurysm. Clinics, 63 (1), 59-66. (Level 3 Evidence - Independent study)
Tan, E. L., Pereles, B. D., Horton, B., Shao, R., Zourob, M., & Ong, K. G. (2008). Implantable Biosensors for Real-time Strain and Pressure Monitoring. Sensors, 15 (8), 6396-6406. (Level 5 Evidence)
U. S. Food and Drug Administration. (2006, October). Center for Devices and Radiological Health. 510(k) Premarket Notification Database. K061046. Retrieved September 25, 2009 from http://www.accessdata.fda.gov/cdrh_docs/pdf6/K061046.pdf.
U. S. Food and Drug Administration. (2008, August). Center for Devices and Radiological Health. 510(k) Premarket Notification Database. K082191. Retrieved September 28, 2009 from http://www.accessdata.fda.gov/cdrh_docs/pdf8/K082191.pdf.
ORIGINAL EFFECTIVE DATE: 5/10/2008
MOST RECENT REVIEW DATE: 12/8/2011
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