Rupture of surgically thrombosed abdominal aortic aneurysm

Micromechanical and Ultrastructural Properties of Abdominal Aortic Aneurysms

Abdominal aortic aneurysms are a common condition of uncertain pathogenesis that can rupture if left untreated. Current recommended thresholds for planned repair are empirical and based entirely on diameter. It has been observed that some aneurysms rupture before reaching the threshold for repair whilst other larger aneurysms do not rupture. It is likely that geometry is not the only factor influencing rupture risk. Biomechanical indices aiming to improve and personalise rupture risk prediction require, amongst other things, knowledge of the material properties of the tissue and realistic constitutive models. These depend on the composition and organisation of the vessel wall which has been shown to undergo drastic changes with aneurysmal degeneration, with loss of elastin, smooth muscle cells, and an accumulation of isotropically arranged collagen. Most aneurysms are lined with intraluminal thrombus, which has an uncertain effect on the underlying vessel wall, with some authors demonstrating a reduction in wall stress and others a reduction in wall strength. The majority of studies investigating biomechanical properties of ex vivo abdominal aortic aneurysm tissues have used low-resolution techniques, such as tensile testing, able to measure the global material properties at the macroscale. High-resolution engineering techniques such as nanoindentation and atomic force microscopy have been modified for use in soft biological tissues and applied to vascular tissues with promising results. These techniques have the potential to advance the understanding and improve the management of abdominal aortic aneurysmal disease.

Rupture of a Totally Occluded Abdominal Aortic Aneurysm

Totally occluded aortic aneurysm is a rare pathology. The medical history and the evolution are unknown. We present a case of a regularly followed up 60-year-old man with chronic thrombosed aneurysm, presenting with mycotic acute rupture. As an original treatment, the patient was treated by aortic ligation without distal revascularization. A literature review from 1974 to 2015 enhances the contemporary understanding of the pathology, by exploring the thrombus interaction, pressure, and the wall shear stress. The literature review confirms the poor prognosis and concludes of a necessary closer follow-up for chronic occluded aneurysm.

Two-Center German Experience with Aortic Endografting

Purpose:

To report the results of a two-center study of endovascular abdominal aortic aneurysm (AAA) exclusion using a polyester-covered nitinol stent-graft.

Methods:

Candidates were evaluated with arteriography and computed tomography. Criteria for endovascular therapy were a proximal aortic neck > 10 mm in length and < 25 mm in diameter, no bilateral internal iliac artery involvement in the aneurysm, no markedly tortuous common iliac arteries (CIAs) or CIAs < 7 mm in diameter, and no superior mesenteric artery occlusive disease. Patients were treated with the Mialhe Stentor and Vanguard stent-grafts in either tube or bifurcated versions.

Results:

Between August 1994 and November 1996, 149 patients (mean age 67 years, range 49 to 90) were admitted to the study. Overall primary technical success (aneurysm exclusion without endoleak) was 87% (130 patients): 78% (7 patients) for tube grafts and 88% (123 patients) for bifurcated endografts. The rate of local, remote, or systemic complications was 10.8%, with a 30-day mortality rate of 0.7%. During an average 13.5-month follow-up, there were no late deaths. Four of 20 endoleaks sealed spontaneously, 14 were treated with endoluminal techniques, and 2 remain untreated by patient request. Three graft limb thromboses occurred; one was treated surgically, one with lytic therapy, and one was untreated. Secondary patency was 96%.

Conclusions:

Endoluminal repair of infrarenal AAAs using straight or bifurcated grafts is a feasible alternative to conventional surgical repair. Longer follow-up and more experience with refined endograft models will elucidate the durability of this endovascular approach to treating AAAs.

Endovascular Management of Visceral Artery Aneurysm

Purpose:

To retrospectively review our experience with visceral artery aneurysms (VAAs) treated with percutaneous coil embolization techniques.

Methods:

Patient records were retrospectively reviewed between 1988 and 1998 for VAA cases treated with catheter-based techniques. Nine patients (5 women; mean age 64 ± 11 years) with 12 (8 false and 4 true) VAAs were identified. The majority (67%) of these patients presented with symptoms of aneurysm rupture. The etiology of the aneurysm was iatrogenic in 4, pancreatitis in 4, and idiopathic in 4. Ten cases involved the hepatic artery; the other 2 aneurysmal arteries were the middle colic and the gastroduodenal. Selective and superselective catheter techniques were used to obtain access to the VAA. A variety of microcoils were delivered to entirely fill saccular aneurysms, whereas fusiform aneurysms were thrombosed by occluding the inflow and outflow vessels.

Results:

Aneurysm exclusion was achieved in 9 (75%) of the 12 cases. The 3 technical failures resulted from the inability to cannulate the aneurysm neck. Coil embolization of the neck of the aneurysm sac did not result in occlusion of the native vessel, with a single exception. No procedure-related complications or deaths were noted. All patients remained symptom free during a mean follow-up of 46.0 ± 29.6 months.

Conclusions:

Percutaneous transcatheter coil embolotherapy is an effective alternative to open surgery for the management of VAAs. This therapy may decrease the morbidity and mortality associated with an open surgical procedure in patients with ruptured aneurysms and pseudoaneurysms, selectively thrombosing the aneurysm while preserving flow in the native vessel.

Incidental discovery of a chronically thrombosed abdominal aortic aneurysm: case report and literature review

Chronic spontaneously thrombosed abdominal aortic aneurysms (AAAs) are rare. We present a patient with a completely thrombosed abdominal aortic aneurysm found incidentally on imaging for evaluation of unrelated abdominal pain. The patient was asymptomatic with regards to the aneurysm due to extensive collateralization of the intercostal and lumbar arteries to the bilateral hypogastric and internal mammary arteries to the common femoral arteries bilaterally. Follow-up imaging after 10 months showed no aneurysmal change. Further study is needed regarding indications for elective repair, medical therapy, and surveillance modality and schedule for patients with chronically occluded AAAs as these patients are at risk for aneurysm rupture and thrombus propagation.

Acute thrombosis of an abdominal aortic aneurysm followed by delayed rupture associated with bacterial infection

Sudden thrombosis of an abdominal aortic aneurysm (AAA) is distinctly rare and is associated with up to 50% mortality. Almost equally rare is infection of a preexisting AAA. We report an extremely unusual case of an AAA that thrombosed leading to acute limb ischemia. This was followed several months later by a delayed rupture of the thrombosed AAA associated with an Escherichia coli infection. We suspect the aortic thrombus was hematogenously seeded by a urinary tract infection. A review of the literature revealed that bacterial infection of a previously thrombosed AAA, leading to a delayed rupture, has not been previously reported.

Intrathrombotic pressure of a thrombosed abdominal aortic aneurysm

In a case of thrombosed abdominal aortic aneurysm, intraluminal and intrathrombotic pressures were simultaneously measured 3 cm distal to the left renal vein level (#1), at the inferior mesenteric artery level (#2) (3 cm distal to #1), 3 cm distal to #2 (#3), and at the aortic bifurcation level (#4) (3 cm distal to #3). The intraluminal pressure (at #1) was 154/72 (101) mmHg, and the intrathrombotic pressures at #2, #3, and #4 were 138/77 (100), 137/74 (97), and 135/68 (96) mmHg, respectively. The percentages of the systolic and mean intrathrombotic pressures to the intraluminal pressure were 90% and 99% at #2, 89% and 96% at #3, and 88% and 95% at #4, respectively. The mural thrombus of an aneurysm does not significantly decrease the pressure on the aneurysmal wall, even in a thrombosed aneurysm.

Visceral Artery Aneurysms

Visceral artery aneurysms (VAA) frequently present as life-threatening emergencies. The purpose of this study was to review our experience with VAA treatment. Between 1988 and April 2002, 31 VAA were treated in 28 patients (14 males, 14 females) with average age of 55 +/- 15 years. The most common locations were the splenic artery (16) and the hepatic artery (7). Three patients underwent emergency surgery, 22 patients had elective open surgery, and 7 patients underwent endovascular treatment. In the surgical group the perioperative mortality rate was 3.6%. The perioperative morbidity rate was 7.1% (one case of respiratory distress manifested in the immediate postoperative period and one urgent case of bilious fistula). In the endovascular group none of the patients died; the perioperative morbidity rate was of 14.3% (one case of hepatic artery thrombosis after failure of gastroduodenal artery aneurysm embolization). Failure of the procedure was 42.9% (3 cases of aneurysm recanalization). In conclusion, we believe that an aggressive surgical approach is justified, even in the case of asymptomatic VAA, because of the low morbidity and mortality rates. Endovascular treatment should be reserved for selected cases.

Minimally invasive retroperitoneal approach for the treatment of infrarenal aortic disease

PURPOSE

In order to decrease complications and improve postoperative recovery, we have developed a minimally invasive retroperitoneal approach (MIRPA) for the treatment of infrarenal aortic disease. This study was carried out to define the limitations and applicability of this technique in the treatment of aortoiliac occlusive disease (AIOD) and abdominal aortic aneurysms (AAAs).

METHODS

From November 2000 to February 2004, 150 patients with AAA (n = 130) or AIOD (n = 20) were prospectively included in the study. The procedure consisted in a standard aneurysmorrhaphy or bypass procedure performed through a video assisted left minilombotomy.The main outcomes measured were mortality, complications, operative time, aortic cross-clamp time, time to solid diet, and length of intensive care unit and hospital stay.

RESULTS

Operative mortality was 0.7 %. Nonfatal postoperative complications occurred in 12 patients (8%). Conversion to a standard procedure was necessary in 3 patients. Mean operative time was 207 +/- 57 minutes (AAA) and 224 +/- 55 minutes (AIOD). Mean aortic cross-clamp time was 76 +/- 26 minutes (AAA) and 48 +/- 21 minutes (AIOD). Median resumption of regular diet was 2 days. Median length of stay in the intensive care unit was 1 day and in the hospital 8 days.

CONCLUSION

Our results suggest that MIRPA is a safe and effective minimally invasive procedure in the treatment of infrarenal aortic disease.

Rupture of a previously thrombosed thoracoabdominal aneurysm

Spontaneous thrombosis of abdominal aortic aneurysms is rare. A patient with a 12-cm thoracoabdominal aneurysm developed sudden thrombosis of his aneurysm. He was treated with axillobifemoral bypass. He went on to rupture 7 months later. While spontaneous thromboses of abdominal aortic aneurysms have been previously reported, we did not find any reports of a thrombosed thoracoabdominal aneurysm or a subsequent rupture of this type of aneurysm. The literature on thrombosis of aneurysms is reviewed as well as proposed etiologies for thrombosis and subsequent rupture. We believe that resectional therapy may be warranted even in high-risk patients.

Internal iliac aneurysm rupture into the rectum following endovascular exclusion: an unusual cause of massive lower gastrointestinal bleeding

PURPOSE

To report a rare iliorectal fistula following endovascular treatment of an internal iliac aneurysm.

CASE REPORT

A 76-year-old man developed lower gastrointestinal bleeding 3 months after successful endovascular exclusion of a left internal iliac aneurysm with coil embolization, attempted stent-grafting, ligation of the distal external iliac artery, and a femorofemoral crossover bypass. Aortography showed no clear intestinal bleeding point, but demonstrated recanalization and continued perfusion of the aneurysm. At laparotomy, an iliorectal fistula was detected. The common iliac artery was ligated proximally, the aneurysm sac was opened, and the back-bleeding internal iliac artery branches were oversewn. The rectum was closed primarily. He made an uneventful recovery.

CONCLUSIONS

An iliorectal fistula is an extremely rare and unlikely complication of coil occlusion of an iliac aneurysm. A high index of suspicion for the diagnosis is of paramount importance. Periodic imaging in these patients is required to detect recanalization and continuing aneurysm expansion.

Infrarenal rupture of an abdominal aortic aneurysm, previously repaired using an endoaneurysmorrhaphy technique

Unusual as well as well-known complications can occur after aortic reconstruction. In an effort to heighten awareness of these possibilities, a case is presented of a 71-year-old male who was brought to the emergency department with severe back pain of 2 days duration and hypotension. He had undergone repair of an infrarenal abdominal aortic aneurysm 6 years earlier. An emergency computed tomography scan demonstrated a 10-cm abdominal aortic aneurysm extending from just above the celiac axis, through the aortic bifurcation, with retroperitoneal and intraperitoneal hematoma. He was found at operation to have extension of his aneurysmal disease proximally, with complete separation of the proximal suture line, and rupture of the distal aortic wall. Since the aneurysm had been closed around the graft at the time of the original operation, his aneurysm had essentially been restored, and the diseased wall was again exposed to the tensile stresses from the pulsatile column of blood. Emergency repair was successful, despite postoperative complications including myocardial infarction, and later rupture of an iliac artery aneurysm. Patients presenting with signs and symptoms consistent with a ruptured abdominal aortic aneurysm after previous repair should be addressed aggressively with computed tomography if it is immediately available and the diagnosis is in doubt. The patient should then undergo an immediate operation. Such recurrence, although rare, must always be considered a possibility. Similar scenarios may be encountered secondary to endoleaks occurring after endoluminal aortic repairs.

Pressure measurements in closed aneurysmal sac during abdominal aortic aneurysm resection

PURPOSE

This study determined the relationship between closed aneurysmal sac pressure (ASP) and mean blood pressure (BP) during open abdominal aortic aneurysm (AAA) resection and evaluated the contribution of inferior mesenteric and lumbar artery blood flow to ASP after proximal and distal clamping.

METHODS

We measured ASP after proximal and distal clamping by placing an 18-gauge needle connected to a BP transducer into the excluded aneurysmal sac in 25 consecutive patients from April 1999 to August 2000. Simultaneous measurement of the mean systemic BP was also recorded. The ratio of ASP to mean BP in relation to the number of actively bleeding lumbar arteries (N-LA), diameter of the AAA (D-Cm), and volume of the thrombus in the AAA (Vol-TA) were recorded.

RESULTS

The mean ASP was 43.32 +/- 15.19 mm Hg, with an ASP to mean BP ratio of 0.47 +/- 0.15. The N-LA in the closed aneurysmal sac ranged from 0 to 6 (mean, 3.4 +/- 1.78). The D-Cm as determined by means of computed tomography (CT) scan of the aorta ranged from 5 to 8 cm in its largest anteroposterior/transverse diameter. The average Vol-TA was 6.15 +/- 4.49 mL. Inferior mesenteric artery blood flow contributed to ASP in three patients (12%). There was no correlation between ASP to mean BP ratios and the N-LA (P =.127), D-Cm (P =.882), or Vol-TA (P =.252).

CONCLUSION

Closed ASP and ASP ratios are highly variable and do not correlate with N-LA, D-Cm, or the Vol-TA.

Embolization of hypogastric artery aneurysm: 17 cases

Surgical management of hypogastric artery aneurysm is associated with high morbidity due to hemorrhage and ischemia. Occlusion by embolization is an attractive alternative treatment. Between 1991 and 1995, we used Gianturco coils to embolize 17 hypogastric aneurysms in 14 patients. All patients were men with a mean age of 77 years. Ten patients had previously undergone aortic repair. Complete occlusion of the aneurysm was achieved in 16 cases but placement of an iliac stent was required in 1 case. Embolization failed in one case involving rupture of a large aneurysm. No complications were observed. Moderate buttock claudication was noted after bilateral embolization in three cases. Embolization of hypogastric artery aneurysm using coils resolves the long-term problems associated with surgical ligation. Extensive aneurysm of the origin to the bifurcation is the main indication for nonresective treatment but embolization can also be a useful alternative to open surgery for high-risk patients. Availability of stent grafts may extend the indication for endovascular treatment.

Experimental study of the influence of endoleak size on pressure in the aneurysm sac and the consequences of thrombosis

BACKGROUND

This was an experimental study of endovascular aortic surgery, looking at the relationship between the size of an endoleak, pressure in the aneurysm sac and the effect of thrombosis produced by coagulation.

METHODS

In three pigs, 16 saccular aneurysms were connected to the aorta by various side branches with different diameters and lengths ('endoleaks'). Mean and pulse pressures were measured in the systemic circulation as well as in the aneurysm sac during the experiment. Duplex ultrasonography was used to determine whether the endoleak and the aneurysm were patent or thrombosed. Thrombosis was influenced by systemic tranexamic acid, fibrinogen in the aneurysm sac, Gelfoam in both endoleak and aneurysm sac, and by Histoacryl glue in the endoleak.

RESULTS

With an open endoleak, the mean pressure in the aneurysm and the aorta was identical. Mean aneurysm pressure was lower with a thrombosed endoleak and was related to the diameter of the endoleak. Pulse pressure was recorded in the aneurysm sac when there was an open endoleak and a non-thrombosed aneurysm, and was related to the diameter of the open endoleak. Thrombosed endoleaks never produced pulse pressure in the aneurysm. If Histoacryl and Gelfoam induced thrombosis of the endoleak, the decrease in mean aneurysm pressure was identical to that resulting from the spontaneous thrombosis of endoleaks.

CONCLUSION

An open endoleak results in systemic arterial pressure in the aneurysm sac. Pulse pressure is detected if the aneurysm is patent, but absent if there is complete or partial thrombosis of the aneurysm. Endoleak thrombosis, either spontaneous or by embolization, is accompanied by a decrease in mean pressure and the absence of pulse pressure in the aneurysm sac. The extent to which these experimental findings are comparable to the clinical situation represents a field of further research.

Midterm experience with the endovascular treatment of isolated iliac aneurysms

PURPOSE

This report describes our 5-year experience with the endovascular repair of isolated iliac aneurysms and pseudoaneurysms.

METHODS

Between June 1993 and July 1998, 40 isolated iliac aneurysms and pseudoaneurysms were treated with endovascular grafts in 39 patients. Thirty-seven aneurysms were treated with endovascular grafts composed of polytetrafluoroethylene grafts and balloon expandable stents, and the other three underwent repair with a polycarbonate urethane endoluminal graft.

RESULTS

All the patients underwent initially successful endovascular treatment of isolated iliac aneurysms and pseudoaneurysms and were followed from 1 to 51 months (mean, 18 months). The 4-year primary patency rate was 94.5% +/- 10%. The perioperative complications included one episode of distal embolization, an episode of colonic ischemia, five episodes of kinking or compression of the endovascular graft, and one early postoperative graft thrombosis. There was only one perioperative death in a patient whose aneurysm ruptured in the operating room just before endovascular repair. The median postoperative length of hospital stay was 3.0 +/- 1.3 days in this group of patients at moderate and high risk. The long-term complications included one graft thrombosis and two endoleaks. One small endoleak was followed until the patient died of unrelated causes, and the other one led to aneurysm rupture in the only patient temporarily lost to follow-up examination. This patient successfully underwent treatment in the standard open surgical fashion. To date, all the other aneurysms have remained stable or have decreased in size during the follow-up examinations with duplex or contrast-enhanced computed tomographic scans.

CONCLUSION

Endovascular repair of iliac aneurysms and pseudoaneurysms is a safe and effective technique with good midterm results in patients at standard and high risk. These grafts are particularly beneficial for patients with medical, surgical, or anatomic contraindications for open surgical repair.

Occluding aortic endoluminal stent graft combined with extra-anatomic axillofemoral bypass as alternative management of abdominal aortic aneurysms for patients at high risk with complex anatomic features: a preliminary report

PURPOSE

To describe an exclusion endoluminal technique for management of abdominal aortic aneurysms among high-risk patients with complex anatomic features.

METHODS

From January 1995 to December 1996, among 143 patients with infrarenal abdominal aortic aneurysm treated by means of endograft placement, 9 (6.3%) had complex aortic or aortoiliac morphologic features. For these patients, the endograft was delivered through a femoral cutdown in an occluding aortoiliac configuration. The contralateral iliac artery was occluded with an iliac endograft. Axillofemoral bypass grafting was performed. Computed tomographic scans were obtained regularly.

RESULTS

There was 1 postoperative death of severe arrhythmia. All aneurysms were found to be affected by thrombosis on immediately postoperative computed tomographic scans, except in 1 patient with a proximal leak, which was managed successfully with angiographic embolization. The mean follow-up time was 12 months. Aortic aneurysm diameter decreased from 2 mm at 6 months (2 patients) to 6 mm at 12 months (6 patients). All axillofemoral bypass grafts are patent.

CONCLUSIONS

Placement of an occluding endograft associated with axillofemoral bypass grafting is a good alternative for patients at high risk with complex anatomic features. Longer-term follow-up study is needed to evaluate this endoluminal technique.

Endoleakage after stent-graft treatment of abdominal aneurysm: implications on pressure and imaging--an in vitro study

BACKGROUND

Endoleakage is a fairly common problem after endovascular repair of abdominal aortic aneurysm and may prevent successful exclusion of the aneurysm. The consequences of endoleakage in terms of pressure in the aneurysmal sac are not exactly known. Moreover, the diagnosis of endoleakage is a problem because visualization of endoleaks can be difficult.

METHOD

With an ex vivo model of circulation with an artificial aneurysm managed by means of a tube graft, studies were performed to evaluate precisely known diameters of endoleaks with both imaging techniques (computed tomography and digital subtraction angiography) and pressure measurements of the aneurysmal sac. The experiments were performed without endoleak (controls) and with 1.231-French (0.410 mm), 3-French (1 mm), and 7-French (2.33 mm) endoleaks. Pressure and imaging were evaluated in the absence and presence of a simulated open lumbar artery. The pressure in the prosthesis and in the aneurysmal sac were recorded simultaneously. Digital subtraction angiography with and without a Lucite acrylic plate, computed tomographic angiography, and delayed computed tomographic angiography were performed. For the first experiments, the aneurysmal sac was filled with starch solution. All tests were repeated with fresh thrombus in the aneurysmal sac.

RESULTS

Each endoleak was associated with a diastolic pressure in the aneurysmal sac that was identical to diastolic systemic pressure, although the pressure curve was damped. At digital subtraction angiography without a Lucite acrylic plate, the 1.231-French (0.410 mm) endoleak was visualized without an open lumbar artery. When a Lucite acrylic plate was added, the endoleak was not visible until a lumbar artery was opened. In the presence of thrombus within the aneurysmal sac, all endoleaks were not visualized at digital subtraction angiography. At computed tomographic angiography, all endoleaks were not visualized in the absence of a thrombus mass in the aneurysmal sac. In the presence of thrombus within the aneurysmal sac, the 1.231-French (0.410 mm) endoleak became visible after opening of a simulated lumbar artery. At delayed computed tomographic angiography, all endoleaks were visualized without and with thrombus.

CONCLUSION

Every endoleak, even a very small one, caused pressure greater than systemic diastolic pressure within the aneurysmal sac. However, small endoleaks were not visualized with digital subtraction angiography and computed tomographic angiography, whereas all endoleaks were visualized with a delayed computed tomographic angiography protocol. We believe that follow-up examinations after stent graft placement for aortic aneurysms should focus on pressure measurements, but until this is clinically feasible, delayed computed tomographic angiography should be performed.

Complementary surgical/interventional techniques for nonresective management of "inoperable" aneurysms: a second look

Induced thrombosis ("nonresective" therapy) of aortic aneurysms by distal arterial ligation, coil/wire embolization, and extraanatomic bypass was devalued by anecdotal reports emerging during the mid-1980s. Nevertheless, we have recently found the technique to be life-saving in occasional cases and worth revisiting. Since 1990, standard aortic aneurysm repair has been performed in 231 patients (99.1% survival), endovascular aortic aneurysm repair in 6 patients (83.3% survival), and combined surgical/interventional "nonresective" repair of a variety of aneurysms in 10 patients (100% survival). Mean age of the group was 67.9 years. Repair was performed for aortoiliac aneurysms (4), common iliac aneurysms (3), internal iliac aneurysms (2), and a large proximal subclavian artery pseudoaneurysm (1). Four of the patients had been explored and declared to be "inoperable" (retroperitoneal fibrosis) prior to transfer to the Columbia-Presbyterian Medical Center. All patients survived. Aneurysm rupture has not occurred in any patient, but one patient with a presumably thrombosed subclavian pseudoaneurysm presented 26 months postcoil-induced thrombosis with progressive aneurysm enlargement due to incomplete aneurysm thrombosis and required repair using circulatory arrest. Eight of the patients remain alive (80%) at a mean follow-up of 40.3 months (range 14-88 months). Two patients died of malignancy (30 months) and cardiac disease (15 months). It is concluded that combined surgical/interventional techniques can be life-saving in the rare instances when conventional or endovascular aneurysm repair is not advisable but that complete aneurysm thrombosis is essential and occasionally difficult to achieve. Since small proximal portions of the aneurysm may remain patent and not be visualized on magnetic resonance imaging (MRI) or computed tomography (CT) scans, contrast angiographic documentation of complete aneurysm thrombosis is essential prior to hospital discharge and close follow-up is necessary to ascertain long-term adequacy of the repair. Incomplete thrombosis is suspected as a major factor in earlier reports of aneurysm rupture after seemingly successful nonresective therapy.

Two-center German experience with aortic endografting

PURPOSE

To report the results of a two-center study of endovascular abdominal aortic aneurysm (AAA) exclusion using a polyester-covered nitinol stent-graft.

METHODS

Candidates were evaluated with arteriography and computed tomography. Criteria for endovascular therapy were a proximal aortic neck > 10 mm in length and < 25 mm in diameter, no bilateral internal iliac artery involvement in the aneurysm, no markedly tortuous common iliac arteries (CIAs) or CIAs < 7 mm in diameter, and no superior mesenteric artery occlusive disease. Patients were treated with the Mialhe Stentor and Vanguard stent-grafts in either tube or bifurcated versions.

RESULTS

Between August 1994 and November 1996, 149 patients (mean age 67 years, range 49 to 90) were admitted to the study. Overall primary technical success (aneurysm exclusion without endoleak) was 87% (130 patients): 78% (7 patients) for tube grafts and 88% (123 patients) for bifurcated endografts. The rate of local, remote, or systemic complications was 10.8%, with a 30-day mortality rate of 0.7%. During an average 13.5-month follow-up, there were no late deaths. Four of 20 endoleaks sealed spontaneously, 14 were treated with endoluminal techniques, and 2 remain untreated by patient request. Three graft limb thromboses occurred; one was treated surgically, one with lytic therapy, and one was untreated. Secondary patency was 96%.

CONCLUSIONS

Endoluminal repair of infrarenal AAAs using straight or bifurcated grafts is a feasible alternative to conventional surgical repair. Longer follow-up and more experience with refined endograft models will elucidate the durability of this endovascular approach to treating AAAs.

Aneurysm pressure following endovascular exclusion

OBJECTIVES

To assess the effect of stent-graft implantation on the pressure within an abdominal aortic aneurysm.

METHODS

Aneurysm exclusion was performed using an aorto-uniiliac stent-graft in eight patients. Following stent-graft implantation, pressure measurements were performed through a catheter adjacent to the graft in the aneurysm. This "aneurysm pressure" was compared with radial arterial pressure.

RESULTS

The pressure was lower in the aneurysm than in the radial artery, in all cases. Mean aneurysm pressure was 36.5/33.8 mmHg, while mean radial arterial pressure was 118.5/50.5 mmHg (p < 0.05, for both systolic and diastolic pressures). These findings corresponded with a reduction in the palpable abdominal pulse, and an absence of perigraft perfusion on follow-up computerised tomography.

CONCLUSION

Stent-graft implantation produces a fall in the pressure within an abdominal aortic aneurysm.

Results of endoluminal grafting in an experimental aortic aneurysm model

We studied the impact of an endoluminally placed stented aortic graft on the geometry of a surgically created abdominal aortic dilation (AAD) in nonatherosclerotic mongrel dogs. Patulous iliac vein patch infrarenal aortoplasty produced a fusiform AAD, doubling the aorta diameter. Lumbar and mesenteric aortic tributaries were preserved and no mural thrombus formed. AADs created in 23 dogs were endoluminally excluded through transfemoral placement of a thin-wall Dacron graft 4 +/- 2 months later. Balloon-expandable stents were used to anchor each end of the graft to the aorta. The graft was crimped radially in its body and longitudinally at its ends to provide longitudinal and radial expandability in these respective zones. Serial color duplex, angiography, and direct caliper measurements were made. Before graft placement, a 19% +/- 11% diameter growth was observed. At graft placement, flow arrest immediately occurred in the space between the graft and the AAD intima in all cases. Although microscopic recanalization of the thrombus in this space was seen at sacrifice 6 and 12 months later, no macroscopic duplex flow was imaged. A 10% +/- 11% reduction in AAD diameter was measured at 6 months (p < 0.001), with no further reduction at 12 months. Graft dimensions remained stable. No anastomotic leaks developed. AAD growth stopped during the first year after effective endoluminal exclusion in normotensive dogs despite patent side branches (< 1.5 mm internal diameter) and no mural thrombus at the time of graft placement. Whether microscopic recanalization of the thrombus that forms outside the graft has an impact after 1 year remains to be seen.

Transfemoral endovascular repair of iliac artery aneurysms

PURPOSE

This report evaluates the application of transfemoral endovascular repair of iliac artery aneurysms.

PATIENTS AND METHODS

Over a 20-month period, 11 patients with serious comorbid illnesses and a total of 14 iliac artery aneurysms were treated with endovascular grafts composed of polytetrafluoroethylene conduits combined with balloon expandable iliac artery stents (Palmaz). Nine right common, 3 left common, and 2 right internal iliac artery aneurysms were treated. The patients were men between 58 and 89 years of age (mean 72). Eight patients had isolated aneurysms and 3 had multiple iliac artery aneurysms.

RESULTS

Endovascular iliac grafts were successfully placed in all 11 patients. No procedural deaths occurred. Follow-up ranged from 3 to 21 months (mean 11). No acute or late graft thromboses occurred.

CONCLUSIONS

Transluminally placed endovascular stented grafts can be used to successfully exclude iliac artery aneurysms from the circulation while maintaining lower-extremity arterial perfusion. However, longer follow-up in more patients is necessary to confirm the durability of this technique.

Ligation and extraanatomic arterial reconstruction for the treatment of aneurysms of the abdominal aorta

PURPOSE

Since Blaisdell et al. first described axillobifemoral bypass and aortic exclusion to treat patients at high risk with abdominal aortic aneurysms in 1965, this approach has been controversial. To help define the appropriate application of this procedure, the recent experience of the authors was reviewed.

METHODS

Twenty-six patients underwent operation between March 1980 and August 1992. Mean age was 71 +/- 7 years. Average aneurysm diameter was 7.0 +/- 1.5 cm. Sixty-nine percent of the aneurysms were symptomatic; 21% were suprarenal. All patients had serious comorbid factors. All underwent axillobifemoral bypass with iliac artery ligation; the infrarenal aorta was also ligated in 62%.

RESULTS

There were two postoperative deaths (7.7%). One- and two-year survival rates were 59% and 38%, respectively. Three patients died of aneurysm rupture (11.5%); the aorta had not been ligated in two of these patients. The remaining late deaths were due to comorbid conditions. Extraanatomic bypass grafts thrombosed in five patients; no limbs were lost.

CONCLUSIONS

Axillobifemoral bypass without aortic ligation does not effectively reduce the risk of aneurysm rupture. However, axillobifemoral bypass with aortic ligation is an acceptable treatment for patients with severe medical problems and symptomatic, anatomically complicated, or large abdominal aortic aneurysms. Because the risk of aneurysm rupture is not completely eliminated, this procedure should be reserved for patients with high-risk aneurysms who would not tolerate direct aortic replacement.

Morphology of small aneurysms: definition and impact on risk of rupture

BACKGROUND

Parietal characteristics of small aortic aneurysms predictive of increased risk of rupture are unknown.

METHODS

Prospective morphologic evaluation was performed in 135 consecutive cases of small (< 5 cm) abdominal aortic aneurysm. Twelve cases (9%) were found to be ruptured and sent for emergency surgery. The remaining 123 patients were evaluated with ultrasonography, angiography, and intraoperatively during elective surgery. Ninety-six (78%) also underwent computerized tomography (CT) scanning. The evaluation assessed the thickness of the endoluminal thrombus and arterial wall as well as the presence of saccular outpouchings ("blisters"). Also noted were any areas of impending rupture, defined as discontinuity of the arterial wall with only a thrombus preventing rupture.

RESULTS

Blisters were discovered intraoperatively in 12 aneurysms. Digital subtraction angiography (DSA) revealed 3 (25%) of these preoperatively. Eleven of the patients with blisters were examined preoperatively with CT scanning, which detected 3 blisters (27%). Both endoluminal thrombus and wall thickness were measurable by CT scan but not ultrasonography. The incidence of impending rupture was significantly greater in patients with blisters than in those without (71% versus 29%, P = 0.0001). The incidence of impending rupture was similar whether the amount of endoluminal thrombus was more or less than 2 cm (57% versus 40%, P = 0.386). Rupture was no more frequent when aneurysmal walls were thicker or thinner than 0.3 cm (14% versus 20%, P = 0.719). In an analysis using logistic regression, the presence of a blister was the only independent morphologic predictor of impending rupture (P = 0.001, Wald = 15).

CONCLUSION

In patients with small aneurysms, increased attention should be directed to the preoperative detection of blisters.

Delayed rupture of an internal iliac artery aneurysm following proximal ligation for abdominal aortic aneurysm repair

This is a report of a patient presenting with a contained rupture of an internal iliac aneurysm following proximal ligation after abdominal aortic aneurysm repair three years earlier. The patient presented with a large pelvic mass with symptoms of urgency, frequency, dysuria, tenesmus and fevers associated with anemia. Following evacuation of the aneurysm and direct suture ligation of the distal branches of the internal iliac artery, the patient's aortic graft was covered with omentum which also filled the pelvic cavity. The importance of proximal and distal control of aneurysms and/or the importance of complete luminal control of internal iliac artery aneurysms is emphasized by this case.

Transfemoral intraluminal graft implantation for abdominal aortic aneurysms

This study reports on animal experimentation and initial clinical trials exploring the feasibility of exclusion of an abdominal aortic aneurysm by placement of an intraluminal, stent-anchored, Dacron prosthetic graft using retrograde cannulation of the common femoral artery under local or regional anesthesia. Experiments showed that when a balloon-expandable stent was sutured to the partially overlapping ends of a tubular, knitted Dacron graft, friction seals were created which fixed the ends of the graft to the vessel wall. This excludes the aneurysm from circulation and allows normal flow through the graft lumen. Initial treatment in five patients with serious co-morbidities is described. Each patient had an individually tailored balloon diameter and diameter and length of their Dacron graft. Standard stents were used and the diameter of the stent-graft was determined by sonography, computed tomography, and arteriography. In three of them a cephalic stent was used without a distal stent. In two other patients both ends of the Dacron tubular stent were attached to stents using a one-third stent overlap. In these latter two, once the proximal neck of the aneurysm was reached, the sheath was withdrawn and the cephalic balloon inflated with a saline/contrast solution. The catheter was gently removed caudally towards the arterial entry site in the groin to keep tension on the graft, and the second balloon inflated so as to deploy the second stent. Four of the five patients had heparin reversal at the end of the procedure. We are encouraged by this early experience, but believe that further developments and more clinical trials are needed before this technique becomes widely used.

Surgical treatment of abdominal aortic aneurysm in the high-risk patient

In an attempt to define the preoperative risk factors that predictably influence mortality after aneurysmectomy, this study reviews the surgical management of abdominal aortic aneurysms in a series of 110 consecutive patients who underwent elective resection. The preoperative risks to be added to the present study included pulmonary insufficiency, renal dysfunction, advanced age of over 80 years, ischemic heart disease, and associated other diseases such as thoracic aneurysms, atherosclerosis of the limbs and malignant tumors. Forty-six patients had one of these risk factors (one-risk group), 17 had two (two-risk group), and 9 had three (three-risk group). The operative mortality rates were 4.2 per cent for the high-risk patients and 0 per cent for the patients at no risk. As the number of risk factors increased, aneurysm repair was associated with an increased operative mortality; being 2.2 per cent in the one-risk group, 5.9 per cent in the two-risk group and 11.1 per cent in the three-risk group. The common risk factor in patients who died after aneurysmectomy was pulmonary insufficiency which induced prolonged periods of assisted ventilation. Thus, the optimal management of high-risk patients, particularly those with pulmonary insufficiency, may reduce the mortality after aneurysmectomy.

Repair of abdominal aortic aneurysms in high-risk patients

Today, repair of an abdominal aortic aneurysm with interposition prosthetic graft replacement is the only reliable method of preventing aneurysm rupture. The Mayo experience demonstrates that this repair also can be accomplished in high-risk patients with very acceptable morbidity and low mortality rates. However, it must be emphasized that these results are related not only to the surgical procedure itself but also to vigorous perioperative medical support, including intraoperative pharmacologic enhancement of cardiac function, intra-aortic balloon counterpulsation if necessary, and intensive postoperative pulmonary management. When resources are available for intensive intraoperative and postoperative support, direct graft repair is the treatment of choice for high-risk patients with abdominal aortic aneurysms.

Treatment options for aneurysms in high-risk patients

The increasing prevalence of aneurysms in an aging population bears with it increasing numbers of patients who are less than optimal candidates for resection. It is likely that the majority of such patients can undergo standard resection, either by referral to a center where the management of the elderly chronically ill is commonplace or by providing intensive preoperative metabolic, cardiac, pulmonary, and nutritional resuscitation. Such preoperative preparation might well include coronary revascularization or carotid endarterectomy. For the occasional patient in whom medical comorbidity is advanced and fixed, or in whom rapid aneurysm expansion or worsening symptoms mandate immediate management, yet operative risk for standard aneurysm resection seems inordinately high, several nonresective options have been identified and tested. Among these options, aneurysm exclusion appears to have significantly better results (in terms of lower rates of operative mortality and subsequent aneurysm rupture) than distal aneurysm ligature. A more recent technique, aneurysm bypass, may have potential but has not been tested for a long enough period, or by an adequate number of surgeons, to have established itself as a nonresective option. Clinical judgment, technical expertise, and a willingness to seek assistance and consultation remain the hallmarks of the optimal management of the patient with an abdominal aortic aneurysm.

Surgical management of abdominal aortic aneurysm in the high-risk patient

Surgical therapy of aortic abdominal aneurysms has progressed in recent years to the point where the presence of an aortic aneurysm greater than 4 cm is an indication for surgical repair. The high-risk patients require careful preoperative evaluation and intensive postoperative supervision if significant morbidity and mortality are to be kept to less than 6 to 7 per cent.

Transfemoral placement of intraluminal polyurethane prosthesis for abdominal aortic aneurysm

Because of the significant mortality associated with the conventional surgical approach to abdominal aortic aneurysms (AAA) in the high risk patients and in those with ruptured aneurysms, we have developed a new approach to this problem, intraluminal aneurysm exclusion. This was achieved by an intraluminal prosthesis which approximated the diameter of the aorta above and below the aneurysm and is inserted through the femoral artery. The prosthesis consisted of biomedical grade elastomeric polyurethane with a NITINOL and/or stainless steel frame and was designed in such a configuration that it could be compressed inside a 15 F catheter and then regain its original shape after being discharged inside the aorta. The polyurethane prosthesis tolerated static pressures in excess of 300 Torr. Aneurysmal aortas were created in three adult sheep using large knitted Dacron pathches (6 X 9 cm) sewn onto a longitudinal aortotomy. After 4-6 weeks, an intraluminal prosthesis was passed transfemorally to the location of the aortic aneurysm. Following satisfactory placement and expansion of the prosthesis, a laceration was produced in the aneurysmal wall. No bleeding developed, which confirmed the integrity of the prosthesis in excluding the aneurysm from the aorta proper. Pulsation in the iliac arteries indicated the presence of aortic blood flow through the prosthesis. Autopsy examination demonstrated directly that the prosthesis was open and that its two ends were fixed in the aorta above and below the aneurysm. The study has demonstrated that intraluminal AAA exclusion could be achieved with an intraluminal polyurethane prosthesis inserted through the femoral artery.