Suprarenal endograft fixation and medium-term renal function: systematic review and meta-analysis

Endovascular repair for infra-renal aortic aneurysms with supra-renal fixation endoprosthesis: Results and outcomes

OBJECTIVE

The main objective of this paper is to evaluate the outcomes regarding endoleaks, reinterventions, and death related to aneurysm complications in patients submitted to endovascular repair (EVAR) for abdominal aortoiliac aneurysm (AAA) using Endurant II (Medtronic) and Zenith Flex (Cook) endografts.

METHODS

This was a prospective, consecutive cohort study of patients with AAA who underwent EVAR with the use of Endurant II stent graft and Zenith Flex endograft.

RESULTS

A total of 156 patients submitted to EVAR were evaluated. The perioperative mortality was 5.1%, 8 patients. The median clinical follow-up period was 760 ± 80 days. There were 28 patients (17.9%) submitted to urgent repair of the aneurysm (symptomatic expansion or rupture) and 128 patients (82.1%) submitted to elective repair. There were 36 cases (23.1%) of later endoleak and most of them are Type II endoleaks (21 patients, 13.4%). There were 12 cases of Type I endoleak. Moreover, regarding limb graft occlusion (LGO), there were 9 patients (5.8%). The overall survival rate in Kaplan-Meier analysis at 720 days was 84.8% in the total cohort. The freedom from reintervention rate in Kaplan-Meier analysis at 720 days was 92.7% in the total cohort. The linear regression analysis for survival rates showed that chronic kidney disease (p = .03; hazard ratio (HR) = 2.82, CI = 1.07-4.44) was the only factor related to poorer survival rates in both univariate and multivariate analyses. The linear regression analysis showed that the presence of endoleaks (p < .001, HR = 6.69, CI = 2.26-8.48) and limb graft occlusion (p < .001, HR = 8.02, CI = 1.60-9.99) were related to reintervention in both univariate and multivariate analyses.

CONCLUSION

In this present study, supra-renal fixation endograft devices were safe and efficient in treating AAA, with satisfactory results and no renal compromise. The linear regression analysis showed that the presence of endoleaks and limb graft occlusion were related to higher reintervention rates in both univariate and multivariate analyses.

The effect of suprarenal graft fixation during EVAR on short- and long-term renal function

OBJECTIVE

The effect of suprarenal fixation (SR) compared to infrarenal fixation (IR) on renal function during endovascular aneurysm repair (EVAR) remains controversial. This study aims to compare the renal outcomes between fixation types in short- and long-term follow-up.

METHODS

Patients undergoing EVAR for infrarenal abdominal aortic aneurysm between 2005 and 2013 were included. Estimated glomerular filtration rate (eGFR) was measured at baseline and during a follow-up of 5 years. A decline in renal function was defined as a ≥ 20% decrease in eGFR. Changes in eGFR were compared between SR and IR groups at 1-7 days, 30 days, and 1-5 years postoperatively. Preoperative renal insufficiency was defined as eGFR < 60mL/min/1.73m², and those patients were included in the subanalyses.

RESULTS

A total of 358 patients were included. Among these, 267 (74.6%) had SR and 91 (25.4%) had IR fixation. A decline in renal function occurred more commonly after SR than after IR in 1-7 days postoperatively (p = .009), but no difference was noticed at 30 days and 1-5 years. Regardless of the fixation method, renal function steadily decreased steadily over time after EVAR (estimate -3.13 per a year, 95% confidence interval -3.40- -2.85, p < .001). Patients with pre-existing renal insufficiency were included in subgroup analyses, and those with SR were more often found to have a decline in eGFR 5 years postoperatively than their counterparts with IR (59.5% vs 20.0%, p = .036).

CONCLUSION

An immediate postoperative decline in renal function was seen more often after SR fixation than IR fixation but this difference was transient. SR fixation is a safe method for patients with normal renal function. Long-term results seems to favor IR over SR in patients with pre-existing renal insufficiency.

Proximal fixation of endovascular aortic device may not be associated with renal function decline after abdominal aortic aneurysm repair

OBJECTIVE

Significant debate exists among providers who perform endovascular abdominal aortic aneurysm repair (EVAR) regarding the renal function change between suprarenal (SuF) and infrarenal (InF) fixation devices. The purpose of this study is to review our institution's experience using these devices in terms of renal function.

METHODS

This is a retrospective review of all elective EVARs performed within a three-site health system (Florida, Minnesota, and Arizona) during the period of 2000 to 2018. The primary outcome was renal function decline on long-term follow-up depending on the anatomical fixation of the device (SuF vs InF). Secondary outcomes were length of hospitalization (LOH) and progression to hemodialysis. Multivariable regression analysis was performed to test for associations affecting LOH.

RESULTS

There were 1130 elective EVARs included in our review. Of those, 670 (59.3%) had SuF and 460 (40.7%) InF. Long-term follow-up was 4.8 ± 3.7 years, and the rate of change in creatinine and estimated glomerular filtration rate (eGFR) were not statistically significant among groups (SuF vs InF). LOH was higher in those individuals with a SuF device (3.4 ± 2.2 vs 2.3 ± 1.0 days; P < .001). Ten patients with chronic kidney disease progressed to hemodialysis at 6.7 ± 3.8 years from EVAR. On Kaplan-Meier analysis, patients with chronic kidney disease with SuF were more likely to progress to hemodialysis (P = .039). On multivariable regression, female sex (Coef, 2.4; 95% confidence interval [CI], 0.17-0.41; P = .02), SuF (Coef, 9.5; 95% CI, 0.11-1.11; P < .0001), and intraoperative blood loss of greater than 150 mL (Coef, 15.4; 95% CI, 0.11-1.76; P < .0001) were predictors of prolonged LOH.

CONCLUSION

Our three-site, single-institution data indicate that, although the starting eGFR was statistically lower in those individuals undergoing elective EVAR with InF, device fixation type did not affect the creatinine and eGFR on long-term follow-up. However, caution should be exercised at the time of abdominal aortic aneurysm repair in those individuals who already presented with renal dysfunction.

Time-to-Event Analysis of the Impact of Endovascular Aortic Aneurysm Repair on Chronic Renal Decline

BACKGROUND

Although randomized studies have revealed the long-term outcomes of the endovascular repair (ER) of abdominal aortic aneurysm (AAA) compared to open repair (OR), there is controversy surrounding chronic renal decline (CRD) after ER. This study reviewed our propensity-matched cohorts of ER and OR to compare CRD rates using a time-to-event analysis. The ER groups undergoing suprarenal (SR) or infrarenal (IR) proximal fixation were also compared with the OR group.

METHODS

This retrospective review of infrarenal AAA repair was conducted from June 2007-December 2017. Patients with ≥1 year of follow-up were included. Cases of supra/pararenal AAAs, infectious AAAs, rupture, or severe chronic kidney disease (CKD) (estimated glomerular filtration rate (eGFR) <15 mL/min/1.73 m² or dependence on renal replacement therapy) were excluded. CRD was defined as eGFR decline of >20% or de novo hemodialysis during follow-up. Patients treated with ER (ER group) and OR (OR group) were propensity-score matched for age, sex, comorbidities, ejection fraction, respiratory function, and baseline eGFR. Kaplan-Meier analysis compared the freedom from CRD rates of the matched cohorts (mER and mOR groups). Patients treated with SR and IR fixation devices (SR and IR groups) were also separately matched to the OR group, followed by analysis.

RESULTS

In total, 1087 patients underwent elective AAA repair. Among them, 944 (512 ER and 432 OR) were enrolled. The ER group was older than the OR group (median age 79 vs 71; P<0.001). The ER group had significantly lower baseline eGFR and more comorbidities than the OR group. Among 187 propensity-score matched pairs (187 mER and 187 mOS patients), background characteristics, including age and baseline eGFR, were comparable, but median renal function follow-up was significantly longer in the mER group than in the mOR group (48 vs 26 months; P<0.001). CRD was observed in 57 patients in the mER group and 30 patients in the mOR group. Kaplan-Meier analysis of the freedom from CRD showed no significant difference between the matched groups (P=0.268); however, in the later follow-up of >4 years, CRD was more common in the mER group. The matched analyses between the OR group and specific fixation groups, comprising 102 OR-SR and 73 OR-IR pairs, demonstrated no significant differences in CRD.

CONCLUSIONS

Compared to OR, there was no significant impact of ER on CRD at up to 4 years, supporting the safety of ER in terms of the mid-term renal outcome of our present clinical practice.

Renal Dysfunction Following Elective Endovascular Aortic Aneurysm Repair

Abdominal aortic aneurysm (AAA) is a degenerative disease of the aortic wall with potentially fatal complications. Open repair (OR) was considered the gold standard, until the emergence of endovascular aneurysm repair (EVAR), which is less invasive and equally (if not more) effective. As the popularity of endovascular procedures grows, related complications become more evident, with kidney damage being one of them. Although acute kidney injury (AKI) following EVAR is relatively common, its true incidence is still uncertain. Also, there is insufficient data concerning long-term renal outcomes after EVAR, especially with repeated contrast agent exposure. Despite the lack of firm evidence on the effectiveness of individual strategies, it is evident that prevention of AKI following EVAR requires a multifactorial approach. This review focuses on recent findings based on human studies regarding the current evidence of renal impairment after EVAR, its quantification and strategies for its prevention.

Repair of abdominal aortic aneurysms: preoperative imaging and evaluation

Imaging is a critical component of the pre-procedure evaluation and planning of endovascular aneurysm repair (EVAR). Imaging is the mainstay for proper assessment of procedural candidacy, relevant vascular anatomy, device selection, and surgical approach. Computed tomography angiography (CTA) has long been considered the preferred modality for pre-operative imaging and evaluation prior to EVAR. Recently, advances in image quality and software technology have further enhanced the proceduralist's ability to plan and perform EVAR. In this review, we highlight the current state of the art to provide interventionalists a contemporary assessment of the available tools for pre-operative imaging and evaluation prior to EVAR.

Abdominal aortic aneurysms: pre- and post-procedural imaging

Abdominal aortic aneurysm (AAA) is a relatively common, potentially life-threatening disorder. Rupture of AAA is potentially catastrophic with high mortality. Intervention for AAA is indicated when the aneurysm reaches 5.0-5.5 cm or more, when symptomatic, or when increasing in size > 10 mm/year. AAA can be accurately assessed by cross-sectional imaging including computed tomography angiography and magnetic resonance angiography. Current options for intervention in AAA patients include open surgery and endovascular aneurysm repair (EVAR), with EVAR becoming more prevalent over time. Cross-sectional imaging plays a crucial role in AAA surveillance, pre-procedural assessment, and post-EVAR management. This paper will discuss the current role of imaging in the assessment of AAA patients prior to intervention, in evaluation of procedural complications, and in long-term follow-up of EVAR patients.

Meta-analysis of Renal Function Following Infrarenal EVAR using Suprarenal or Infrarenal Fixation Devices

OBJECTIVE/BACKGROUND

The effect of suprarenal (SR) as opposed to infrarenal (IR) fixation on renal outcomes post-endovascular aneurysm repair (EVAR) remains controversial. This meta-analysis aims to update current understanding of this issue.

METHODS

A prior meta-analysis was updated through a Preferred Reporting Items for Systematic reviews and Meta-Analyses search for additional studies published in the last 3 years reporting on renal dysfunction or related outcomes post-EVAR. Random effects meta-analysis was undertaken using SPSS.

RESULTS

A total of 25 non-randomised studies comparing SR with IR fixation were included, totalling 54,832 patients. In total, 16,634 underwent SR and 38,198 IR. Baseline characteristics, including age, baseline estimated glomerular filtration rate, diabetes, cardiac disease, and smoking, were similar between the groups. There was a small but significant difference in outcomes for renal dysfunction at the study end point (SR 5.98% vs. IR 4.83%; odds ratio [OR] 1.29, 95% confidence interval [CI] 1.18-1.40 [p < .001]); however, at 30 days and 12 months there was no significant difference, and this did not hold up to sensitivity analysis. Incidence of renal infarcts (SR 6.6% vs. IR 2.3%; OR 2.78, 95% CI 1.46-5.29 [p = .002]), renal stenosis (SR 2.4% vs. IR 0.8%; OR 2.89, 95% CI 1.00-8.38 [p = .05]), and renal artery occlusion (SR 2.4% vs. IR 1.2%; OR 2.21, 95% CI 1.15-4.25 [p = 0.02]) favoured IR fixation; however, there was no difference in haemodialysis rates.

CONCLUSION

This meta-analysis has identified small but significantly worse renal outcomes in patients having SR fixation devices compared with IR; however, there was no difference in dialysis rates and a small effect on renal dysfunction, which did not stand up to rigorous sensitivity analysis. This should be taken into consideration during graft selection, and further studies must assess renal outcomes in the longer term, and in those with pre-existing renal dysfunction.

Editor's Choice - Renal complications after EVAR with suprarenal versus infrarenal fixation among all users and routine users

BACKGROUND

Previous studies comparing endografts with suprarenal and infrarenal fixation for endovascular abdominal aortic aneurysm repair (EVAR) have found conflicting results and did not account for differences in patient selection. This study aims to evaluate the differences in outcomes among surgeons who routinely use either suprarenal or infrarenal fixation, as well as all surgeons in the Vascular Study Group of New England (VSGNE).

METHODS

All patients undergoing EVAR in the VSGNE from 2003 to 2014 were identified. All ruptured aneurysms, repairs with concomitant procedures, and infrequently used stent grafts (<50) were excluded. Suprarenal endografts included Talent, Zenith, and Endurant; infrarenal endografts included AneuRx and Excluder. Grafts were compared among surgeons who used only one type of endograft (suprarenal or infrarenal) for >80% of cases, as well as all surgeons. Multivariate regression and Cox hazard models were utilised to account for patient demographics, comorbidities, operative differences, and procedure year.

RESULTS

This study identified 2574 patients (suprarenal, 1264; infrarenal, 1310) with 888 endografts placed by routine users (suprarenal, 409; infrarenal, 479). There were no differences in baseline comorbidities, including the estimated glomerular filtration rate, between suprarenal and infrarenal fixation, or between patients with endografts placed by routine and non-routine users. Patients treated with suprarenal endografts received more contrast than all users (102 mL vs. 100 mL, p = .01) and routine users (110 mL vs. 88 mL, p < .01), but other vascular and operative details were similar. Among all users, patients treated with suprarenal grafts had higher rates of creatinine increase >.5 mg/dL (3.7% vs. 2.0%, p = .01), length of stay >2 days (27% vs. 19%, p < .01), and discharge to a skilled nursing facility (9.2% vs. 6.7%, p = .02). There were no differences in 30 day or 1 year mortality. Following adjustment, suprarenal stent grafts remained associated with an increased risk of renal deterioration (OR 2.0; 95% CI 1.2-3.4) and prolonged length of stay (OR 1.8; 95% CI 1.4-2.2). Among routine users, suprarenal fixation was also associated with higher rates of renal dysfunction (3.7% vs. 1.3%, p = .02; OR 2.9; 95% CI 1.1-7.8).

CONCLUSION

Despite potential differences in patient selection, endografts with suprarenal fixation among all users and routine users were associated with higher rates of renal deterioration and longer length of hospital stay. Longer-term data are needed to determine the duration and severity of renal function decline and to identify potential benefits of decreased migration or endoleak.

Comparison of Renal Complications between Endografts with Suprarenal and Infrarenal Fixation

OBJECTIVES

Surgeons have multiple grafts options available for the endovascular treatment of abdominal aortic aneurysm (EVAR), and some hypothesize that suprarenal fixation endografts may result in higher rates of renal complications than infrarenal endografts. This study aimed to compare the outcomes of contemporary suprarenal and infrarenal endografts.

METHODS

The Targeted Vascular Module of the National Surgical Quality Improvement Project was utilised to identify patients undergoing EVAR for infrarenal aneurysm from 2011 to 2013. Pre-operative and operative variables and 30 day outcomes were compared among suprarenal (Zenith and Endurant) and infrarenal fixation devices (Excluder). Renal complications included creatinine increase > 2 mg/dL or new dialysis, as defined by NSQIP. Multivariate regression was completed to account for patient demographics, comorbidities, and operative characteristics.

RESULTS

A total of 3587 patients were evaluated including 2273 (63%) with suprarenal grafts and 1314 (37%) with infrarenal grafts. Patients with suprarenal grafts were less commonly white (84% vs. 88%, p < .01) and more commonly male (83% vs. 80%, p = .03). There were no differences in age or comorbidities. Renal complications (1.1% vs. 0.1%, p < .01) and length of stay more than 2 days (34% vs. 25%, p < .01) occurred more commonly after suprarenal fixation. After adjustment, suprarenal grafts had significantly higher rates of renal complications (OR, 12.0; 95% CI, 1.6-91) and length of stay more than 2 days (OR, 1.4; 95% CI, 1.2-1.7).

CONCLUSION

Overall rates of renal complications following EVAR are low. Patients selected for suprarenal stent grafts are at increased risk of renal complications and prolonged length of stay, which may be due to selection bias, deployment techniques, or the presence of a bare stent overlying the renal arteries. Further studies are necessary to evaluate the mechanism and duration of renal dysfunction and important long-term outcomes of interest.

Progression to stage 3 and 4 chronic kidney disease and risk factor stratification following endovascular aortic aneurysm repair

Background

Risk of progression to various stages of chronic kidney disease (CKD) after endovascular aortic aneurysm repair (EVAR) is unknown. This study estimates progression rates to stage 3 and 4 CKD after EVAR and identifies potential predictors for progression.

Methods

EVAR cases (2006–2012) were retrospectively reviewed. Freedom of progression to CKD was estimated using Kaplan–Meier analysis, and predictors for progression were identified using Cox proportional hazards model.

Results

Two hundred and twelve consecutive patients at a single academic institution underwent EVAR for infrarenal aneurysms. Estimated freedom from progression to stage 3 CKD was 80%, 76%, and 63% at 6, 12, and 18 months, respectively, and for stage 4, 97%, 96%, and 93% at 6, 12, and 18 months, respectively. Stage 3 CKD predictors of progression included age (odds ratio (OR): 1.106, p = 0.001), diabetes (OR: 3.052, p = 0.04), perioperative use of angiotensin converting enzyme inhibitors or angiotensin receptor blockers (OR: 3.249, p = 0.02), and operative blood loss (OR: 1.002, p < 0.01). Stage 4 predictors included preoperative hemoglobin (OR: 0.473, p = 0.04) and baseline renal function (OR: 0.928, p = 0.001). Intraoperative contrast administration did not impact CKD development.

Conclusions

Progression to stage 3 CKD after EVAR occurs more frequently and at a higher rate compared with progression to stage 4. Different risk factors are associated with progression to each of those stages of CKD.

Quantified Aortic Luminal Irregularity as a Predictor of Complications and Prognosis After Endovascular Aneurysm Repair

Atheromatous degeneration of the aorta is considered to be a risk factor for postoperative embolic complications after endovascular treatment, and is associated with a high incidence of vascular events in the long term. We devised a method to quantify the shagginess of the aorta using contrast-enhanced computed tomography (CT) images. This study examined the method's validity and prognostic usefulness in patients undergoing elective endovascular abdominal aortic aneurysm repair (EVAR). We retrospectively investigated 427 patients who underwent elective EVAR between 2007 and 2013. Preoperative contrast-enhanced CT images with a slice thickness of 1 mm were analyzed using a workstation, and the degree of aortic luminal irregularity from the level of the left subclavian artery ostium to that of the celiac artery ostium was quantified by computing a shagginess score. We compared the computed scores with subjective visual assessments of aortic shagginess. Subsequently, we evaluated the relationship between the computed scores and postoperative prognosis. The shagginess scores were significantly correlated with the visual assessments of the aortic lumen, which were performed by 5 experienced vascular surgeons (rho ranged from 0.564-0.654, all P < 0.001). Multiple logistic regression analysis demonstrated that the shagginess score was independently associated with the development of renal impairment within a month after EVAR (odds ratio, 2.78; 95% confidence interval [CI], 1.83-4.22, P < 0.001). The shagginess score was significantly higher in patients who suffered postoperative intestinal and peripheral ischemic complications, as compared with those who did not (P < 0.001). The mean postoperative follow-up period was 1207 ± 641 days. Cox proportional hazards regression showed that the shagginess score was a significant independent predictor of all-cause and cardiovascular mortality (hazard ratio [HR], 1.37; 95% CI, 1.09-1.72, P = 0.007, and HR, 1.51; 95% CI, 1.04-2.18, P = 0.030, respectively). The results suggest that the shagginess score provides a quantitative reflection of aortic luminal irregularity. It may serve as a useful predictive factor for postoperative renal function deterioration, embolic complications, and long-term mortality after elective EVAR.

Endovascular repair of abdominal aortic aneurysms: vascular anatomy, device selection, procedure, and procedure-specific complications

Abdominal aortic aneurysm (AAA) is abnormal dilatation of the aorta, carrying a substantial risk of rupture and thereby marked risk of death. Open repair of AAA involves lengthy surgery time, anesthesia, and substantial recovery time. Endovascular aneurysm repair (EVAR) provides a safer option for patients with advanced age and pulmonary, cardiac, and renal dysfunction. Successful endovascular repair of AAA depends on correct selection of patients (on the basis of their vascular anatomy), choice of the correct endoprosthesis, and familiarity with the technique and procedure-specific complications. The type of aneurysm is defined by its location with respect to the renal arteries, whether it is a true or false aneurysm, and whether the common iliac arteries are involved. Vascular anatomy can be divided more technically into aortic neck, aortic aneurysm, pelvic perfusion, and iliac morphology, with grades of difficulty with respect to EVAR, aortic neck morphology being the most common factor to affect EVAR appropriateness. When choosing among the devices available on the market, one must consider the patient's vascular anatomy and choose between devices that provide suprarenal fixation versus those that provide infrarenal fixation. A successful technique can be divided into preprocedural imaging, ancillary procedures before AAA stent-graft placement, the procedure itself, postprocedural medical therapy, and postprocedural imaging surveillance. Imaging surveillance is important in assessing complications such as limb thrombosis, endoleaks, graft migration, enlargement of the aneurysm sac, and rupture. Last, one must consider the issue of radiation safety with regard to EVAR.

A systematic review and meta-analysis indicates underreporting of renal dysfunction following endovascular aneurysm repair

Deterioration in renal function has been described after endovascular repair of abdominal aortic aneurysms (EVRs). The etiology is multifactorial and represents an important therapeutic target. A need exists to quantitatively summarize incidence and severity of renal dysfunction after EVR to allow better-informed attempts to preserve renal function and improve life expectancy. Here a systematic search was performed using Medline and Embase for renal function after EVR applying PRISMA statements. Univariate and multivariate random-effects meta-analyses were performed to estimate pooled postoperative changes in serum creatinine and creatinine clearance at four time points after EVR. Clinically relevant deterioration in renal function was also estimated at 1 year or more after EVR. Pooled probability of clinically relevant deterioration in renal function at 1 year or more was 18% (95% confidence interval of 14-23%, I2 of 82.5%). Serum creatinine increased after EVR by 0.05 mg/dl at 30 days/1 month, 0.09 mg/dl at 1 month to 1 year, and 0.11 mg/dl at 1 year or more (all significant). Creatinine clearance decreased after EVR by 5.65 ml/min at 1 month-1 year and by 6.58 ml/min at 1 year or more (both significant). Thus, renal dysfunction after EVR is common and merits attention.

Renal interventions during endovascular aneurysm repair

Renal insufficiency is a risk factor for mortality and morbidity during endovascular aneurysm repair. Multiple changes in practice have occurred to mitigate renal injury and renal dysfunction. Transrenal fixation does carry an increased risk of a decline in renal function in the medium term. Renal stenting for athero-occlusive disease during endovascular aneurysm repair needs careful consideration, as indications have changed and there are unexpected consequences with early vessel occlusion. The growing number of renal interventions during complex endovascular aneurysm repair with the advent of chimney snorkel/periscope techniques and the introduction of fenestrated grafts has shown the resilience of the intervention with relatively low renal issues (approximately 10%), but has also illustrated the need for additional device development.

Current status of endovascular devices to treat abdominal aortic aneurysms

The introduction of endovascular abdominal aortic aneurysm (AAA) repair has revolutionized the therapeutic approach to patients with AAA. Due to an on-going and prolific collaboration between vascular interventionalists and biomedical engineers, the devices used to perform endovascular AAA repair have also changed dramatically. The purpose of this publication is to provide an overview of the currently available and upcoming options for endovascular AAA repair.

Percutaneous revascularization for ischemic nephropathy: the past, present, and future

Occlusion of the renal arteries can threaten the viability of the kidney when severe, in addition to accelerating hypertension and circulatory congestion. Renal artery stenting procedures have evolved from a treatment mainly for renovascular hypertension to a maneuver capable of recovering threatened renal function in patients with “ischemic nephropathy” and improving management of congestive heart failure. Improved catheter design and techniques have reduced, but not eliminated hazards associated with renovascular stenting. Expanded use of endovascular stent grafts to treat abdominal aortic aneurysms has introduced a new indication for renal artery stenting to protect the renal circulation when grafts cross the origins of the renal arteries. Although controversial, prospective randomized trials to evaluate the added benefit of revascularization to current medical therapy for atherosclerotic renal artery stenosis until now have failed to identify major benefits regarding either renal function or blood pressure control. These studies have been limited by selection bias and have been harshly criticized. While studies of tissue oxygenation using blood oxygen level dependent (BOLD) MR establish that kidneys can adapt to reduced blood flow to some degree, more severe occlusive disease leads to cortical hypoxia associated with microvascular rarefication, inflammatory injury and fibrosis. Current research is directed toward identifying pathways of irreversible kidney injury due to vascular occlusion and to increase the potential for renal repair after restoring renal artery patency. The role of nephrologists likely will focus upon recognizing the limits of renal adaptation to vascular disease and identifying kidneys truly at risk for ischemic injury at a time point when renal revascularization can still be of benefit to recovering kidney function.

Risk factors and impact of proximal fixation on acute and chronic renal dysfunction after endovascular aortic aneurysm repair using glomerular filtration rate criteria

BACKGROUND

The incidence of renal impairment relevant to proximal fixation of aortic endograft devices remains unclear.

METHODS

Retrospective cohort of 208 consecutive patients that underwent EVAR from 2006 to 2011. Estimated glomerular filtration rate (eGFR) was based on MDRD study equation. Acute kidney injury (AKI) and chronic kidney disease (CKD) were classified with ADIQ/RIFLE criteria and National Kidney Foundation criteria, respectively. Kaplan-Meier curve was applied to evaluate progression to CKD. Multivariate regression model was fit to identify predictors for developing AKI and CKD.

RESULTS

Suprarenal fixation group (SF) included 110 patients and infrarenal fixation group (IF) included 98 patients. Both groups had similar demographics, baseline eGFR, and renal-protection protocols. There was a trend for decreased use of contrast in IF group (median: 93.5 vs. 103 cc, P = 0.07). AKI occurred in 15% of patients in SF group and 19% of patients in IF group (RR: 1.24, P = 0.47). The freedom from progression to stage 3 or 4 CKD in the SF group was 0.76, 0.72, and 0.49 at 6, 12, and 18 months, respectively, while for IF group was 0.8, 0.73, and 0.68, respectively (P = 0.4). Increasing age (P = 0.07), lengthy procedures (P < 0.001), and baseline renal dysfunction (P < 0.001) were significant predictors for developing CKD. Contrast volume (P < 0.001) and ace-inhibitors (P = 0.07) were predictors for AKI.

CONCLUSION

Proximal fixation type has no significant effect on both acute and chronic renal function. Identification of modifiable perioperative risk factors may be used to improve renal function outcomes.

Computational modeling of shear-based hemolysis caused by renal obstruction

As endovascular treatment of abdominal aortic aneurysms (AAAs) gains popularity, it is becoming possible to treat certain challenging aneurysmal anatomies with endografts relying on suprarenal fixation. In such anatomies, the bare struts of the device may be placed across the renal artery ostia, causing partial obstruction to renal artery blood flow. Computational fluid dynamics (CFD) was used to simulate blood flow from the aorta to the renal arteries, utilizing patient-specific boundary conditions, in three patient models and calculate the degree of shear-based blood damage (hemolysis). We used contrast-enhanced computed tomography angiography (CTA) data from three AAA patients who were treated with a novel endograft to build patient-specific models. For each of the three patients, we constructed a baseline model and endoframe model. The baseline model was a direct representation of the patient's 30-day post-operative CTA data. This model was then altered to create the endoframe model, which included a ring of metallic struts across the renal artery ostia. CFD was used to simulate blood flow, utilizing patient-specific boundary conditions. Pressures, flows, shear stresses, and the normalized index of hemolysis (NIH) were quantified for all patients. The overall differences between the baseline and endoframe models for all three patients were minimal, as measured though pressure, volumetric flow, velocity, and shear stress. The average NIH across the three baseline and endoframe models was 0.002 and 0.004, respectively. Results of CFD modeling show that the overall disturbance to flow caused by the presence of the endoframe struts is minimal. The magnitude of the NIH in all models was well below the accepted design and safety threshold for implantable medical devices that interact with blood flow.

Long-term outcome of endovascular abdominal aortic aneurysm repair

Renal function is a concern

Evaluation of a new disease-specific endovascular device for type B aortic dissection

OBJECTIVE

The study objective was to evaluate the feasibility, safety, and early technical and clinical success rate of a new endovascular device specifically designed for aortic dissection that has recently become available in Europe.

METHODS

From June of 2005 to the present, the Zenith Dissection Endovascular System (William Cook Europe, Bjaerverskov, Denmark) was used in 11 selected patients (all male, with a median age of 58 years [range, 45-76 years]) with type B chronic aortic dissection with a compression or collapse of the true lumen. All procedures were performed under general anesthesia with preoperative cerebrospinal fluid drainage in 4 patients. One-step open surgical supra-aortic vessels re-routing was performed in 6 patients to obtain an adequate proximal landing zone: Left carotid-subclavian artery bypass was performed in 5 patients, and right-to-left common carotid artery bypass and left subclavian to common carotid artery transposition was performed in 1 patient. Clinical follow-up visits and computed tomography scans were obtained at 1, 6, and 12 months, and yearly thereafter.

RESULTS

A secondary technical success was obtained in all patients (100%), and 30-day clinical success was achieved in 10 patients (91%). A type IA entry flow was observed in 1 patient. No mortality was recorded. Occlusion of visceral/renal arteries, retrograde dissections, and device-induced tears in the intimal lamellae were not observed. Periprocedural morbidity included temporary renal failure in 1 patient and postimplantation syndrome with fever and leukocytosis for 23 days in 1 patient. No cases of paraplegia were recorded. At a median follow-up of 12 months (range, 2-30 months), we observed a clinical success rate of 91%. No migration of the device was observed. No late occlusion of the visceral or renal arteries was recorded at follow-up.

CONCLUSION

The perioperative and short-term follow-up results showed that the Zenith Dissection Endovascular System for the treatment of aortic dissection can be safely used without affecting the patency of the branches covered by the bare stent. However, these results need to be validated in a larger group of patients with a mid-term follow-up.