Aneurysm Rupture after EVAR: Can the Ultimate Failure be Predicted?

Preoperative inferior mesenteric artery embolization before endovascular aneurysm repair: decreased incidence of type II endoleak and aneurysm sac enlargement with 24-month follow-up

PURPOSE

To review the effect of preoperative embolization of the inferior mesenteric artery (IMA) before endovascular aneurysm repair (EVAR) on subsequent endoleaks and aneurysm growth.

MATERIALS AND METHODS

Between August 2002 and May 2010, 108 patients underwent IMA embolization before EVAR. Coil embolization was performed in all patients in whom the IMA was successfully visualized and accessed during preoperative conventional angiography. In this cohort, the incidences of type II endoleak, aneurysm sac volume enlargement at 24 months, and repeat intervention were compared with a group of 158 consecutive patients with a patent IMA on preoperative computed tomography angiography but not on conventional angiography, who therefore did not undergo preoperative embolization.

RESULTS

The incidence of type II endoleak was significantly higher in patients not treated with embolization (49.4% [78 of 158] vs 34.3% [37 of 108]; P = .015). The incidence of secondary intervention for type II endoleak embolization was also significantly higher in those who did not undergo embolization (7.6% [12 of 158] vs 0.9% [one of 108]; P = .013). At 24 months, an increase in aneurysm sac volume was observed in 47% of patients in the nonembolized cohort (21 of 45), compared with 26% of patients in the embolized cohort (13 of 51; P = .03). No aneurysm ruptures or aneurysm-related deaths were observed in either group. One patient in the embolization group developed mesenteric ischemia and ultimately died.

CONCLUSIONS

Preoperative embolization of the IMA was associated with reduced incidences of type II endoleak, aneurysm sac volume enlargement at 24 months, and secondary intervention.

[Endoleaks - when is treatment necessary?]

Currently the majority of infrarenal abdominal aortic aneurysm repairs are endovascular procedures using a stent graft. This method continues to be questioned due to an up to 50 % incidence of endoleaks, i.e. the postinterventional persistence of blood flow outside the graft and within the aneurysm sac, potentially bearing the risk of a further increase of the aneurysm diameter and aneurysm rupture. Currently a total of five different endoleak types can be distinguished. Multiphase computed tomography (CT) is the standard imaging method for the detection and classification of endoleaks or alternatively contrast-enhanced ultrasound can be used. The different types of endoleak have very different therapeutic implications. In direct endoleaks (types I and III) the systemic blood pressure is directly transferred to the aneurysm wall which carries a high risk of rupture and in general an immediate intervention is indicated. Indirect endoleaks (types II, IV and V) take a more benign course and in the majority of cases treatment is only necessary when further aneurysm expansion occurs.

[Treatment of abdominal aortic aneurysms]

The treatment of abdominal aortic aneurysms (AAA) has changed significantly since the introduction of endovascular aortic repair (EVAR). In terms of perioperative morbidity and mortality, randomized multicenter trials revealed results in favour of EVAR compared to open reconstruction. However, EVAR is associated with possible late complications caused by endoleaks, stent migration, kinking and/or overstenting of side branches, making life-long follow-up necessary. Since the majority of patients requiring therapy are elderly and exhibit attendant comorbidities, EVAR has become the procedure of choice in those patients with favourable anatomy. Medicamentous and conservative treatment may be relevant in patients with small to medium-sized aneurysms. Since smoking is one of the major risk factors for the development of AAA, all patients should be advised to stop smoking. Studies on long-term statin therapy in patients following surgical AAA repair showed a reduction in both overall and cardiovascular mortality; AAA patients should therefore receive statins for secondary prevention.

Compliance with long-term surveillance recommendations following endovascular aneurysm repair or type B aortic dissection

OBJECTIVE

Lifelong surveillance is recommended for both endovascular aneurysm repair and acute, uncomplicated type B thoracic aortic dissection, though compliance remains a significant challenge. We sought to determine factors associated with failure to obtain recommended surveillance.

METHODS

Patients surviving to discharge who had endovascular repair of thoracic (thoracic endovascular aortic aneurysm repair [TEVAR]) or abdominal aortic aneurysms (endovascular aortic aneurysm repair [EVAR]) or medical management for type B dissections from 2004-2011 were reviewed. Primary end points were compliance with follow-up and need for reintervention. Comorbidities examined included coronary artery disease, congestive heart failure, hypertension, chronic obstructive pulmonary disease, diabetes, and chronic kidney disease. Socioeconomic factors examined were age, sex, distance from hospital, discharge destination (ie, home or skilled nursing facility), and insurance type. Endoleak and sac expansion were recorded, as were complications, including endograft migration, infection or thrombosis, and aneurysm degeneration.

RESULTS

Two hundred four patients, median age 71.9 years, were identified; 171 had EVAR and 33 had type B dissection. EVAR patients included 45 thoracic, 100 abdominal, and 12 thoracoabdominal endografts, as well as 7 iliac artery aneurysm repairs and 7 proximal/distal graft extensions. Median follow-up was 28 ± 10.5 months. Overall, 56% were lost to follow-up, whereas 11% never returned for surveillance after initial hospitalization. Follow-up was compared for each of the comorbidities and socioeconomic factors; none were found to significantly affect follow-up. The known complication rate was 9.3% (n = 19), with reintervention performed in 14% of EVAR/TEVAR patients. Thirty-eight percent of medically managed patients with type B dissections eventually required surgical intervention. All-cause 5-year mortality was 27% as determined by the Social Security Death Index.

CONCLUSIONS

Despite a significant rate of reintervention following EVAR, TEVAR, and type B dissection, long-term compliance with surveillance is limited. In addition, predicting who is at risk of being lost to follow-up remains difficult. If current recommendations for lifelong surveillance are to be followed, coordinated protocols are required to capture EVAR, TEVAR, and type B dissection patients to ensure optimal follow-up for these patients. However, the lack of survival benefit in those with complete follow-up suggests that further study is needed with regard to ideal duration of long-term follow-up.

Early histological changes in the porcine aortic media after thoracic stent-graft implantation

PURPOSE

To describe the histological findings in the aortic wall 5 days after thoracic endovascular aortic repair (TEVAR) in a porcine model.

METHODS

Two overlapping stent-grafts were implanted in each of 6 juvenile pigs, covering the entire descending thoracic aorta (DTA). On the 5(th) postoperative day, tissue samples were taken from the DTA in each animal. Medial thickness and medial necrosis were quantified and compared to measurements from the aortas of 6 control animals.

RESULTS

Significant medial thinning was observed in stent-covered regions in the test animals. At the proximal landing zone, aortic wall thickness changed from 1387±68 to 782±74 µm within the covered aortic segment (p = 0.028); at the distal landing site, the wall thickness was 365±67 µm within the stent and 501±57 µm distally (p = 0.028). In the overlap zone, the aortic wall measured 524±122 vs. 1053±77 µm in native controls (p = 0.004). Aortic thickness proximal to the graft did not differ from the proximal region of native aortas (1468±96 vs. 1513±80 µm, p = 0.423), but the aorta was significantly thinner distal to the stent (707±38 vs. 815±52 µm, p = 0.004). Laminar necrosis constituted 38%±7% of the media in the proximal landing zone, 54%±4% in the overlap zone, and 46%±13% in the distal landing zone.

CONCLUSION

In this porcine model, significant medial thinning and necrosis of the stented aorta was observed. The findings suggest an early phase of vulnerability of the aortic wall, before scarring and adaptive changes have strengthened the residual aorta.

Rupture of abdominal aortic aneurysm with shrinkage after endovascular repair

An 85-year-old man, who had undergone endovascular abdominal aortic aneurysm repair 8½ years earlier, was transferred to the emergency department with chest pain and transient loss of consciousness. Computed tomography revealed a ruptured abdominal aortic aneurysm with a stent graft inside. His aneurysm was 62 mm in diameter at the endovascular repair, but 45 mm at the rupture site. He was rescued by emergency aneurysmectomy.

Remodeling of proximal neck angulation after endovascular aneurysm repair

OBJECTIVE

This study investigated the remodeling of proximal neck (PN) angulations of abdominal aortic aneurysms (AAAs) after endovascular aneurysm repair (EVAR).

METHODS

A 64-row multidetector computed tomography scan of AAAs treated with EVAR was reviewed, and the PN angulation was measured on a volume-rendered three-dimensional image. The computed tomography scan was examined preoperatively, after EVAR at 1 week, 1 month, 6 months, 1 year, 1.5 years, 2 years, and then yearly. The study enrolled 78 patients, comprising 54 Zenith devices (Cook Medical, Bloomington, Ind) and 24 Excluder devices (W. L. Gore and Associates, Flagstaff, Ariz).

RESULTS

PN angulation was 50° ± 20° preoperatively, and after EVAR was 36° ± 14° at 1 week, 32° ± 14° at 1 year, and 28° ± 13° at 3 years. PN angulations ≤ 60° (n = 70, 77%) were 41° ± 13° preoperatively, 31° ± 12° 1 week after EVAR, 28° ± 12° at 1 year, and 26° ± 13° after 3 years. An angulation >60° (n = 18, 23%) was 78° ± 14° preoperatively, 51° ± 11° 1 week after EVAR, 44° ± 11° at 1 year, and 40° ± 12° after 3 years. The greater the preoperative PN angulation, the greater its reduction immediately after EVAR (r = .72, P < .001). The diameter shrinkage of AAAs with a PN angulation >60° was 3 ± 6 mm after 1 year; a significantly smaller shrinkage than with a PN angulation ≤ 60° (7 ± 7 mm, P < .05). AAAs with a PN angulation >60° had a larger angulation reduction and a smaller diameter shrinkage after the EVAR procedure. The PN angulation of the 54 AAAs treated by Zenith was 49° ± 22° preoperatively, 34° ± 14° 1 week after EVAR, and 25° ± 13° after 3 years. The corresponding angulation of the 24 AAAs treated by Excluder devices was 52° ± 17°, 41° ± 14°, and 38° ± 9°, respectively. The PN angulation reduction of Zenith and Excluder was similar 1 week after the EVAR procedure. Unlike Excluder, however, the PN angulation in Zenith continued to reduce for a long period at a slow pace. There were no significant correlations between PN angulation reduction and diameter change and between PN length and diameter change (P = .86 and .18, respectively).

CONCLUSIONS

Although the instructions for use of most commercially available stent grafts provide for a PN angulation of ≤ 60°, PN angulation was not a major issue in a midterm follow-up of AAAs with adequate PN length for patients in this series who received a Zenith or Excluder graft.

Endotension: rupture of abdominal aortic aneurysm

Aortic endovascular exclusion technique called 'chimney' consists of placing stents through abdominal aortic visceral branches and a prosthesis that excludes the thoraco-abdominal aneurysm. Stents and an aortic endoprosthesis are placed in the renal arteries. This method is primarily used when open surgery is too risky. The mechanism that provides aneurysm sac increase without the visible presence of endoleaks has not been fully elucidated. The expansion of the aneurysm sac, due to endotension, is difficult to diagnose, even with the use of advanced imaging tests. Its diagnosis is made by exclusion. We present a case of a late complication in a high-risk patient after a 'chimney' endovascular procedure. Following the surgery, the patient presented a ruptured aneurysm sac without a visible endoleak. A second intervention was not feasible due to the high risk of occluding all of the branches, and complicated by previous 'chimney'. Endotension is a possible cause of aneurysm rupture and death.

Imaging Surveillance following Endovascular Aneurysm Repair

Endoleaks are unique complications of endovascular aneurysm repair (EVAR) that necessitate lifelong imaging surveillance for the patient. Several imaging modalities may be used to monitor the patient for endoleaks and other complications related to the stent graft. At present, computed tomographic angiography remains the gold standard for the detection of endoleaks. Other modalities that can be used to detect endoleaks include magnetic resonance, ultrasonography, nuclear medicine techniques, and pressure monitoring. In addition, follow-up imaging with digital subtraction angiography is important for endoleak classification and to guide decisions regarding therapy. In this article, we review the classification of endoleaks and discuss the different imaging strategies available for post-EVAR surveillance.

Complete ten-year follow-up after endovascular abdominal aortic aneurysm repair: survival and causes of death

PURPOSE

To analyze the hazard and causes of death after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms during a complete ten year follow-up.

METHODS

This is a retrospective clinical study of 130 consecutive patients undergoing EVAR between 1995 and 1998. One-hundred twenty-one patients (93.1%) were treated with first-generation stentgrafts and nine patients (6.9%) received second-generation devices. All patients completed a follow-up of at least 10 years, unless death occurred before then. Time and causes of death were provided by the Austrian central register of deaths.

RESULTS

The median follow-up was 7.6 years, and the 130 patients had 968.5 person-years of follow-up. The ten-year mortality rate was 62.3%. Cardiovascular events were the most frequent causes of death, with a 3.9 incidence rate per 100 person-years. Cancer death and death due to other causes occurred in 2.1 and 1.8 cases per 100 person-years, respectively. Lethal late aneurysm rupture happened in 4.6% (n=6), which corresponds to an annual incidence rate of 0.6 per 100 person-years. All of those patients had been treated with first-generation devices.

CONCLUSIONS

Cardiovascular events were the most frequent cause of death after EVAR, followed by malignancy and other diseases. The risk of dying from secondary rupture was clearly lower than that of death due to other reasons during ten years after EVAR, even in patients with first-generation stentgrafts.

Experimental models of abdominal aortic aneurysms

Despite being a leading cause of death in the West, the pathophysiology of abdominal aortic aneurysms (AAA) is still incompletely understood. Pharmacotherapy to reduce the growth of small AAAs is limited and techniques for repairing aneurysms continue to evolve. Experimental models play a key role in AAA research, as they allow a detailed evaluation of the pathogenesis of disease progression. This review focuses on in vivo experimental models, which have improved our understanding of the potential mechanisms of AAA development and contributed to the advancement of new treatments.

Intraoperative sac pressure measurement during endovascular abdominal aortic aneurysm repair

PURPOSE

Intraoperative sac pressure was measured during endovascular abdominal aortic aneurysm repair (EVAR) to evaluate the clinical significance of sac pressure measurement.

METHODS

A microcatheter was placed in an aneurysm sac from the contralateral femoral artery, and sac pressure was measured during EVAR procedures in 47 patients. Aortic blood pressure was measured as a control by a catheter from the left brachial artery.

RESULTS

The systolic sac pressure index (SPI) was 0.87 +/- 0.10 after main-body deployment, 0.63 +/- 0.12 after leg deployment (P < 0.01), and 0.56 +/- 0.12 after completion of the procedure (P < 0.01). Pulse pressure was 55 +/- 21 mmHg, 23 +/- 15 mmHg (P < 0.01), and 16 +/- 12 mmHg (P < 0.01), respectively. SPI showed no significant differences between the Zenith and Excluder stent grafts (0.56 +/- 0.13 vs. 0.54 +/- 0.10, NS). Type I endoleak was found in seven patients (15%), and the SPI decreased from 0.62 +/- 0.10 to 0.55 +/- 0.10 (P = 0.10) after fixing procedures. Type II endoleak was found in 12 patients (26%) by completion angiography. The SPI showed no difference between type II endoleak positive and negative (0.58 +/- 0.12 vs. 0.55 +/- 0.12, NS). There were no significant differences between the final SPI of abdominal aortic aneurysms in which the diameter decreased in the follow-up and that of abdominal aortic aneurysms in which the diameter did not change (0.53 +/- 0.12 vs. 0.57 +/- 0.12, NS).

CONCLUSIONS

Sac pressure measurement was useful for instant hemodynamic evaluation of the EVAR procedure, especially in type I endoleaks. However, on the basis of this small study, the SPI cannot be used to reliably predict sac growth or regression.

Rupture of an Abdominal Aortic Aneurysm Post EVAR: A Rare Presentation of Retroperitoneal Liposarcoma

Endoleak is the classical cause of rupture of aneurysms previously treated by endovascular means. We report a rare case of a retroperitoneal liposarcoma (LIS) invading an abdominal aortic aneurysm (AAA), previously treated by endovascular repair (EVAR), causing rupture. Furthermore, a brief discussion of the diagnostic challenges posed by retroperitoneal tumors is presented with a closing note on their management.

Risk of reintervention after endovascular aortic aneurysm repair

BACKGROUND

The role of symptomatic presentation in directing reintervention after endovascular aortic aneurysm repair (EVAR) was investigated.

METHODS

All patients undergoing infrarenal EVAR between 2001 and 2009 were studied. Those needing reintervention were divided into symptomatic and asymptomatic presentations. Kaplan-Meier survival curves were used to calculate freedom from reintervention, and log rank tests for subgroup analyses. Multivariable analysis identified risk factors for reintervention.

RESULTS

The study included 553 patients with a mean(s.d.) age of 75(7) years and aneurysm diameter of 65(13) mm. The 30-day mortality rate was 2.5 per cent. Median follow-up was 31 (range 1-97) months. There were 86 reinterventions in 69 (12.5 per cent) of 553 patients; 41 presented with symptoms and 28 were asymptomatic. Reintervention-free survival rates at 1, 3 and 5 years were 90.1, 85.3 and 81.2 per cent. The reintervention rate was higher in patients who needed an intraoperative adjunct during the index procedure (P = 0.014) and in those who did not have intraoperative computed tomography angiography (P = 0.024). Intraoperative adjuncts were an independent risk factor for future reintervention (hazard ratio 2.62, 95 per cent confidence interval 1.18 to 3.76; P = 0.012).

CONCLUSION

Most patients requiring reintervention presented symptomatically. A high-risk subgroup may be identifiable to rationalize a postoperative surveillance programme.

Increased fluorodeoxyglucose uptake following endovascular abdominal aortic aneurysm repair: a predictor of endoleak?

The main criterion for abdominal aortic aneurysm (AAA) repair is an AAA diameter ≥5.5 cm. However, some AAAs rupture when they are smaller. Size alone may therefore not be a sufficient criterion to determine rupture risk. Fluorodeoxyglucose (FDG) uptake is increased in the presence of inflammation and it was suggested that this may be a better predictor of rupture risk than AAA size. Furthermore, increased FDG uptake following endovascular AAA repair may be an indirect predictor of continuous AAA sac enlargement due to the presence of an endoleak (even if this is not detected by imaging modalities) and/or increased AAA rupture risk. The role of FDG uptake needs to be explored further in the management of AAAs.

Contrast-enhanced ultrasound versus computed tomographic angiography for surveillance of endovascular abdominal aortic aneurysm repair

PURPOSE

To compare diagnostic accuracy between contrast-enhanced ultrasound (US) and computed tomographic (CT) angiography to detect changes in abdominal aortic aneurysm (AAA) size and endoleaks during follow-up after endovascular aneurysm repair (EVAR).

MATERIALS AND METHODS

Between May 2006 and December 2008, 83 patients were consecutively enrolled for contrast-enhanced US and CT angiography imaging during surveillance after EVAR, yielding 127 paired examinations. Comparative analysis was performed for the anteroposterior and transverse maximal diameters of the aneurysm sac and for the presence or absence of endoleak, as determined by US and CT angiography.

RESULTS

Contrast-enhanced US demonstrated significantly more endoleaks, predominantly of type II, compared with CT angiography (53% vs 22% of cases). The number of observed agreements was 77 of 127 (61%), indicating a low level of agreement (kappa value of 0.237). US was as accurate as CT angiography in the assessment of maximal aneurysm sac diameters, as shown by Bland-Altman analyses and low coefficients of variation (8.0% and 8.6%, respectively). The interobserver variability for AAA size measurement by US was low, given the interclass correlation coefficients of 0.99 and 0.98 for anteroposterior and transverse maximal diameters, respectively.

CONCLUSIONS

Contrast-enhanced US may be an alternative to CT angiography in the follow-up of patients after EVAR. As US reduces exposure to the biologic hazards associated with lifelong annual CT angiography, including cumulative radiation dose and nephrotoxic contrast agent load, contrast-enhanced US might be considered as a substitute for CT angiography in the surveillance of patients after EVAR.

Long-term outcome of endovascular abdominal aortic aneurysm repair

Renal function is a concern