Modular Graft Research Articles

Contained Giant Abdominal Aortic Aneurysm Rupture Secondary to Type I and III Endoleaks Requiring Open Repair With Endograft Explantation.

Endovascular aneurysm repair (EVAR) is a minimally invasive treatment for abdominal aortic aneurysms (AAAs). Common complications include endoleaks, which are continued blood flow into the aneurysm sac external to the graft. Type I endoleaks occur proximally or distally, resulting from inadequate seals between the graft and artery. Type III endoleaks stem from defects between components in modular grafts or fabric tears. Re-intervention is indicated for type I and III endoleaks due to pressurization of the aneurysm sac resulting in a high risk of rupture. A 68year-old man presented with an infrarenal AAA and underwent EVAR. He developed a late type I endoleak requiring reintervention with a stent graft cuff, and later presented with a recurrent type I endoleak and type IIIb endoleak. The AAA increased in size to 18cm with contained rupture, requiring emergent endograft explantation and repair with a bifurcated Dacron graft. His postoperative course was uncomplicated.

Two Decades of Endovascular Abdominal Aortic Aneurysm Repair: Enormous Progress With Serious Lessons Learned

The modern open surgical management of abdominal aortic aneurysm (AAA) has changed little since its inception in the 1950s. Endoaneurysmorrhaphy, first described by Rudolph Matas in 1888, involved ligating the branches of an aneurysm from within the aneurysm sac. Approximately 25 years later at the

Movement and Dislocation of Modular Stent-Grafts Due to Pulsatile Flow and the Pressure Difference Between the Stent-Graft and the Aneurysm Sac

To investigate the stability and movement of modular aortic stent-grafts subjected to oscillating forces from pulsatile blood flow, with particular reference to the thoracic aorta. Analytical mathematical modeling was used to understand the forces on modular grafts. In a benchtop experiment, a transparent acrylic box was filled with water to mimic an aneurysm. Two stent-grafts were placed inside the box in a nested, arched configuration where one component was partly inside the other. A pump produced a pulsatile approximately 5-L/min flow of water through the stent-grafts at a mean inlet pressure of approximately 100 mmHg (approximately 13,330 Pa), with systolic and diastolic pressures of approximately 130 and approximately 80 mmHg, respectively (pulse pressure 50 mmHg). The movement of the 2 modular stent-grafts was observed. The curved stent-graft system oscillated transversely when there was zero mean pressure difference between the stent-graft and the aneurysm. As the mean pressure difference was increased, this transverse graft movement was damped and then disappeared. A relatively large pressure difference caused the stent-graft to inflate and become sturdier. In terms of stability, the analytical mathematical model for a 30-mm-diameter Zenith modular stent-graft curved through 90 degrees (with the ends of the graft fixed in place) showed that the modular components will separate at a pressure difference of 0 mmHg for 1 stent segment overlap (20 mm) and at an average 59 mmHg pressure difference for 2 stent overlaps, but the device would not separate at a pressure difference of 90 mmHg for 3 stent overlaps. Transverse cyclic movement of the curved stent-graft system with pulsation indicates a pressurized sac. When the pressure difference is large and there is a blood-tight seal between the aneurysm and the stent-graft, then the transverse movement of the stent-graft is minimal, but the risk for modular separation is highest. Curved thoracic endografts are subject to forces that may cause migration or separation, the latter being more likely if the seal between the graft and the sac is blood tight, if the blood pressure is high, and if the diameter of the graft is small and the sac large. Operators should plan for maximum overlap of modular components when treating large or long thoracic aneurysms.

Surgical Conversion After Endovascular Grafting for Abdominal Aortic Aneurysms

PURPOSE To analyze the indications, results, and technical problems associated with conversion after endoluminal repair of abdominal aortic aneurysms (AAA) based on a 6-year experience in endovascular grafting. METHODS From August 1994 to May 2000, 520 patients with AAA were deemed candidates for endovascular therapy based on data from contrast-enhanced computed tomography and aortography. Any conversions were performed using an open operation modified according to the indication for conversion, elapsed time from the endoluminal repair, and type of endograft (tube, bifurcated, infra-/suprarenal fixation). RESULTS Conversion to open repair was required in 37 (7.1%) cases: 23 tube grafts and 14 bifurcated devices. Seventeen (3.2%) conversions occurred at the original operation and 20 (3.8%) were performed secondarily. Indications for primary conversion were mainly device defects (n = 5) or access problems (n = 5), while secondary conversion was primarily owing to type I endoleak (n = 16). The conversion rate was significantly higher in modular devices (5.9%) than unibody designs (1.4%) (p = 0.003). The rate of primary conversions diminished from 10.9% in 1994-1995 to 2.4% between 1996 and 2000, as did the overall mortality rate, from 8.3% in the first time period to 0% in the second for elective conversions, but emergency operations had 40% mortality. CONCLUSIONS Most AAAs require bifurcated devices for complete exclusion, and older model modular grafts have higher conversion rates. Primary conversion decreases as more experience in endoluminal grafting is acquired. Emergency open repair results in a high mortality rate.

Entrapment of the Limb of an Endovascular Graft: A Peril of Saccular Aneurysms

Endoluminal repair of an infrarenal saccular aortic aneurysm was undertaken with a modular endovascular stent graft in a 74-year-old man. After deployment of the main body and right iliac limb of the graft, an attempt was made to gain guide wire access to the open short left limb of the graft for placement of the left iliac prosthesis. Attempts to gain access to the left limb graft from the left femoral artery area were unsuccessful. Since we were unable to pass the wire into the iliac system or snare it from below, can nulation from the left brachial artery was attempted. This resulted in the guide wire coiling up within the aneurysm. Eventual conversion to an open procedure confirmed that the short open left limb of the modular graft had deployed such that the opening was completely impacted against the inferior wall of the saccular aneurysm, preventing successful passage of a guide wire. The distance from the aortic neck to the base of the aneurysm is generally not considered an important parameter whe...

Geometric changes in aortic endografts over a 2-year observation period.

To report geometric changes in bifurcated aortic endografts observed over a 2-year follow-up period. Twenty-two patients (21 men; mean age 68 years, range 57-83) with abdominal aortic aneurysms were treated with an endovascular stent-graft. Follow-up examinations included spiral computed tomographic scanning postoperatively and at 3, 6, 9, 12, 18, and 24 months after treatment. Geometric changes were measured using 3-dimensional reconstructed images in anteroposterior (AP) and lateral projections. Locations for the measurements were the proximal neck, the midportion of the endograft, and the graft limbs at the origin of the iliac arteries. Lateral changes predominated, demonstrating maximum angles on the side of the inserted left limb. For the proximal neck, the stent angle changed by a mean -0.71 degrees in the AP and 4.0 degrees in the lateral projection. At the midgraft, changes were -0.56 degrees for AP and 12.5 degrees for lateral. The right limb showed an angle of 6.43 degrees in AP and -0.43 degrees in lateral, whereas the left limb angles changed 1.38 degrees in AP and 11.71 degrees in the lateral plane after 2 years. There was no statistically significance difference in these changes from baseline. Aortic endografts are exposed to a significant amount of movement after insertion, but the resultant changes are very inhomogeneous, unpredictable, and ongoing even after 2 years. The most vulnerable location seems to be the attachment zone of the modular graft limb. These geometric changes might be one cause for late complications, including leaks and limb dislocations.

The anatomy of abdominal aortic aneurysms: Implications for sizing of endovascular grafts

To determine the full range of aorto-iliac anatomy of patients with abdominal aortic aneurysms (AAAs) and thence the range of endovascular graft sizes required to deal with the majority of AAAs. Analysis of preoperative spiral CT measurements. One hundred and sixty-eight patients with AAAs. Multiplanar reconstruction measurements were taken of proximal aortic neck diameter and length, lowermost renal artery to the aortic bifurcation distance and length and diameter of common iliac arteries. Based on these measurements a range of graft sizes that would fit the majority of AAAs was determined. Ranges of anatomical variables were as follows: proximal aortic neck diameter 18-30 mm, renal artery to aortic bifurcation distance 93-210 mm, common iliac artery length 13-108 mm, common iliac artery diameter 6-67 mm. Over 750 graft sizes would be required to cover all anatomical combinations using a one-piece aorto-uni-iliac graft. A wide variety of aorto-iliac anatomy exists in patients with AAAs. The large number of graft sizes required to deal with the majority of AAAs makes the production of one-piece endovascular grafts commercially impractical. A proposed two-piece modular graft would allow the majority of AAAs to be treated using only 16 graft sizes.