Abstract Background Aortic arch disease is a challenging clinical problem, especially in high-risk patients, in whom open repair can have morbidity and mortality rates of 30% to 40% and 2% to 20%, ...respectively. Aortic arch chimney (AAC) stents used during thoracic endovascular aortic repair (TEVAR) are a less invasive treatment strategy than open repair, but the current literature is inconclusive about the role of this technology. The focus of this analysis is on our experience with TEVAR and AAC stents. Methods All TEVAR procedures performed from 2002 to 2015 were reviewed to identify those with AAC stents. Primary end points were technical success and 30-day and 1-year mortality. Secondary end points included complications, reintervention, and endoleak. Technical success was defined as a patient's surviving the index operation with deployment of the AAC stent at the intended treatment zone with no evidence of type I or type III endoleak on initial postoperative imaging. The Kaplan-Meier method was used to estimate survival. Results Twenty-seven patients (age, 69 ± 12 years; male, 70%) were identified, and all were described as being at prohibitive risk for open repair by the treating team. Relevant comorbidity rates were as follows: coronary artery disease/myocardial infarction, 59%; oxygen-dependent emphysema, 30%; preoperative creatinine concentration >1.8 mg/dL, 19%; and congestive heart failure, 15%. Presentations included elective (67%; n = 18), symptomatic (26%; n = 7), and ruptured (7%; n = 2). Eleven patients (41%) had prior endovascular or open arch/descending thoracic repair. Indications were degenerative aneurysm (49%), chronic residual type A dissection with aneurysm (15%), type Ia endoleak after TEVAR (11%), postsurgical pseudoaneurysm (11%), penetrating ulcer (7%), and acute type B dissection (7%). Thirty-two brachiocephalic vessels were treated: innominate (n = 7), left common carotid artery (LCCA; n = 24), and left subclavian artery (n = 1). Five patients (19%) had simultaneous innominate-LCCA chimneys. Brachiocephalic chimney stents were planned in 75% (n = 24), with the remainder placed for either LCCA or innominate artery encroachment (n = 8). Overall technical success was 89% (one intraoperative death, two persistent type Ia endoleaks in follow-up). The 30-day mortality was 4% (n = 1; intraoperative death of a patient with a ruptured arch aneurysm), and median length of stay was 6 (interquartile range, 4-9) days. Seven (26%) patients experienced a major complication (stroke, three all with unplanned brachiocephalic chimney; respiratory failure, three; and death, one). Nine (33%) patients underwent aorta-related reintervention, and no chimney occlusion events occurred during follow-up (median follow-up, 9 interquartile range, 1-23 months). The 1-year and 3-year survival is estimated to be 88% ± 6% and 69% ± 9%, respectively. Conclusions TEVAR with AAC can be performed with high technical success and acceptable morbidity and mortality in high-risk patients. Unplanned AAC placement during TEVAR results in an elevated stroke risk, which may be related to the branch vessel coverage necessitating AAC placement. Acceptable midterm survival can be anticipated, but aorta-related reintervention is not uncommon, and diligent follow-up is needed.
Objective Endovascular surgery has revolutionized the treatment of aortic aneurysms; however, these improvements have come at the cost of increased radiation and contrast exposure, particularly for ...more complex procedures. Three-dimensional (3D) fusion computed tomography (CT) imaging is a new technology that may facilitate these repairs. The purpose of this analysis was to determine the effect of using intraoperative 3D fusion CT on the performance of fenestrated endovascular aortic repair (FEVAR). Methods Our institutional database was reviewed to identify patients undergoing branched or FEVAR. Patients treated using 3D fusion CT were compared with patients treated in the immediate 12-month period before implementation of this technology when procedures were performed in a standard hybrid operating room without CT fusion capabilities. Primary end points included patient radiation exposure (cumulated air kerma: mGy), fluoroscopy time (minutes), contrast usage (mL), and procedure time (minutes). Patients were grouped by the number of aortic graft fenestrations revascularized with a stent graft, and operative outcomes were compared. Results A total of 72 patients (41 before vs 31 after 3D fusion CT implementation) underwent FEVAR from September 2012 through March 2014. For two-vessel fenestrated endografts, there was a significant decrease in radiation exposure (3400 ± 1900 vs 1380 ± 520 mGy; P = .001), fluoroscopy time (63 ± 29 vs 41 ± 11 minutes; P = .02), and contrast usage (69 ± 16 vs 26 ± 8 mL; P = .0002) with intraoperative 3D fusion CT. Similarly, for combined three-vessel and four-vessel FEVAR, significantly decreased radiation exposure (5400 ± 2225 vs 2700 ± 1400 mGy; P < .0001), fluoroscopy time (89 ± 36 vs 64 ± 21 minutes; P = .02), contrast usage (90 ± 25 vs 39 ± 17 mL; P < .0001), and procedure time (330 ± 100 vs 230 ± 50 minutes; P = .002) was noted. Estimated blood loss was significantly less ( P < .0001), and length of stay had a trend ( P = .07) toward being lower for all patients in the 3D fusion CT group. Conclusions These results demonstrate that use of intraoperative 3D fusion CT imaging during FEVAR can significantly decrease radiation exposure, procedure time, and contrast usage, which may also decrease the overall physiologic impact of the repair.
Chronic kidney disease (CKD) leads to increased skeletal muscle fatigue, weakness, and atrophy. Previous work has implicated mitochondria within the skeletal muscle as a mediator of muscle ...dysfunction in CKD; however, the mechanisms underlying mitochondrial dysfunction in CKD are not entirely known. The purpose of this study was to define the impact of uremic metabolites on mitochondrial energetics. Skeletal muscle mitochondria were isolated from C57BL/6N mice and exposed to vehicle (DMSO) or varying concentrations of uremic metabolites: indoxyl sulfate, indole-3-acetic-acid, l-kynurenine, and kynurenic acid. A comprehensive mitochondrial phenotyping platform that included assessments of mitochondrial oxidative phosphorylation (OXPHOS) conductance and respiratory capacity, hydrogen peroxide production (
H
O
), matrix dehydrogenase activity, electron transport system enzyme activity, and ATP synthase activity was employed. Uremic metabolite exposure resulted in a ~25-40% decrease in OXPHOS conductance across multiple substrate conditions (
< 0.05,
= 5-6/condition), as well as decreased ADP-stimulated and uncoupled respiratory capacity. ATP synthase activity was not impacted by uremic metabolites; however, a screen of matrix dehydrogenases indicated that malate and glutamate dehydrogenases were impaired by some, but not all, uremic metabolites. Assessments of electron transport system enzymes indicated that uremic metabolites significantly impair complex III and IV. Uremic metabolites resulted in increased
H
O
under glutamate/malate, pyruvate/malate, and succinate conditions across multiple levels of energy demand (all
< 0.05,
= 4/group). Disruption of mitochondrial OXPHOS was confirmed by decreased respiratory capacity and elevated superoxide production in cultured myotubes. These findings provide direct evidence that uremic metabolites negatively impact skeletal muscle mitochondrial energetics, resulting in decreased energy transfer, impaired complex III and IV enzyme activity, and elevated oxidant production.
Objective “Chimney” techniques used to extend landing zones for endovascular aortic repair (chEVAR) have been increasingly reported; however, concerns about durability and patency remain. The purpose ...of this analysis was to examine midterm outcomes of chEVAR. Methods All patients at the University of Florida treated with chEVAR were reviewed. Major adverse events (MAEs) were recorded and defined as any chimney stent thrombosis, type Ia endoleak in follow-up, reintervention, 30-day/in-hospital death, or ≥25% decrease in estimated glomerular filtration rate after discharge. Primary end points included chimney stent patency and freedom from MAE. Secondary end points included complications and long-term survival. Results From 2008 to 2012, 41 patients (age ± standard deviation, 73 ± 8 years; male, 66% n = 27) were treated with a total of 76 chimney stents (renal, n = 51; superior mesenteric artery, n = 16; celiac artery, n = 9) for a variety of indications: juxtarenal, 42% (n = 17, one rupture), suprarenal, 17% (n = 7), and thoracoabdominal aneurysm, 17% (n = 7); aortic anastomotic pseudoaneurysm, 15% (n = 6; three ruptures); type Ia endoleak after EVAR, 7% (n = 3); and atheromatous disease, 2% (n = 1). Two patients had a single target vessel abandoned because of cannulation failure, and one had a type Ia endoleak at case completion (technical success, 93%). Intraoperative complications occurred in seven patients (17%), including graft maldeployment with unplanned mesenteric chimney (n = 2) and access vessel injury requiring repair (n = 5). Major postoperative complications developed in 20% (n = 8). The 30-day mortality and in-hospital mortality were 5% (n = 2) and 7% (n = 3), respectively. At median follow-up of 18.2 months (range, 1.4-41.5 months), 28 of 33 patients (85%) with available postoperative imaging experienced stabilization or reduction of abdominal aortic aneurysm sac diameters. Nine patients (32%) developed endoleak at some point during follow-up (type Ia, 7% n = 3; type II, 10% n = 4; indeterminate, 7% n = 3), and one patient underwent open, surgical conversion. The estimated probability of freedom from reintervention (±standard error mean) was 96% ± 4% at both 1 year and 3 years. Primary patency of all chimney stents was 88% ± 5% and 85% ± 5% at 1 year and 3 years, respectively. Corresponding freedom from MAEs was 83% ± 7% and 57% ± 10% at 1 year and 3 years. The actuarial estimated survival for all patients at 1 year and 5 years was 85% ± 6% and 65% ± 8%, respectively. Conclusions These results demonstrate that chEVAR can be completed with a high degree of success; however, perioperative complications and MAEs during follow-up, including loss of chimney patency and endoleak, may occur at a higher rate than previously reported. Elective use of chEVAR should be performed with caution, and comparison to open and fenestrated EVAR is needed to determine long-term efficacy of this technique.
Open repair of extent II and III thoracoabdominal aortic aneurysms (TAAA) is associated with substantial morbidity. Alternative strategies, such as hybrid operations combining proximal thoracic ...endovascular aortic repair with either staged open distal TAAA repair or visceral debranching (hybrid), as well as fenestrated/branched endografts (FEVAR), have been increasingly reported; however, benefits of these approaches compared with direct open surgery remain unclear. The purpose of this study was to compare outcomes of these three different strategies in the management of extent II/III TAAA.
All extent II/III TAAA repairs (2002-2018) for nonmycotic, degenerative aneurysm or chronic dissection at a single institution were reviewed. The primary end point was 30-day mortality. Secondary end points included incidence of spinal cord ischemia (SCI), complications, unplanned re-operation, 90-day readmission, and out-of-hospital survival. To mitigate impact of covariate imbalance and selection bias, intergroup comparisons were made using inverse probability weighted-propensity analysis. Cox regression was used to estimate survival while cumulative incidence was used to determine reoperation risk.
One hundred ninety-eight patients (FEVAR, 92; hybrid, 40; open, 66) underwent repair. In unadjusted analysis, compared with hybrid/open patients, FEVAR patients were significantly older with more cardiovascular risk factors, but less likely to have a connective tissue disorder or dissection-related indication. Unadjusted 30-day mortality and complication rates were: 30-day mortality, FEVAR 4%, hybrid 13%, open 12% (P = .01); and complications, FEVAR 36%, hybrid 33%, open 50% (P = .11). Permanent SCI was not different among groups (FEVAR 3%, hybrid 3%, open 6%; P = .64). In adjusted analysis, 30-day mortality risk was greater for open vs FEVAR (hazard ratio, 3.6; 95% confidence interval, 1.4-9.2; P = .01) with no difference for hybrid vs open/FEVAR. There was significantly lower risk of any SCI for open vs FEVAR (hazard ratio, 0.3; 95% confidence interval, 0.09-0.96; P = .04); however, no difference in risk of permanent SCI was detected among the three groups. There was no difference in complications or unplanned reoperation, but open patients had the greatest risk of unplanned 90-day readmission. There was a time-varying effect on survival probability, with open repair having a significant survival disadvantage in the first 1 to 6 months after the procedure compared with hybrid/FEVAR patients (Cox model P = .03), but no difference in survival at 1 and 5 years (1- and 5-year survival: FEVAR, 86 ± 3%, 55 ± 8%; hybrid, 86 ± 5%, 60 ± 11%; open 69 ± 7%, 59 ± 8%; Cox-model P = .10).
Extent II/III TAAA repair, regardless of operative strategy, is associated with significant morbidity risk. FEVAR is associated with the lowest 30-day mortality risk compared with hybrid and open repair when estimates are adjusted for preoperative risk factors. These data support greater adoption of FEVAR as first-line therapy to treat complex TAAA disease in anatomically suitable patients who present electively.
Objective The objective of this study was to develop and to validate the Vascular Quality Initiative (VQI) Cardiac Risk Index (CRI) for prediction of postoperative myocardial infarction (POMI) after ...vascular surgery. Methods We developed risk models for in-hospital POMI after 88,791 nonemergent operations from the VQI registry, including carotid endarterectomy (CEA; n = 45,340), infrainguinal bypass (INFRA; n = 18,054), suprainguinal bypass (SUPRA; n = 2678), endovascular aneurysm repair (EVAR; n = 18,539), and open abdominal aortic aneurysm repair (OAAA repair; n = 4180). Multivariable logistic regression was used to create an all-procedure and four procedure-specific risk calculators based on the derivation cohort from 2012 to 2014 (N = 61,236). Generalizability of the all-procedure model was evaluated by applying it to each procedure subtype. The models were validated using a cohort (N = 27,555) from January 2015 to February 2016. Model discrimination was measured by area under the receiver operating characteristic curve (AUC), and performance was validated by bootstrapping 5000 iterations. The VQI CRI calculator was made available on the Internet and as a free smart phone app available through QxCalculate. Results Overall POMI incidence was 1.6%, with variation by procedure type as follows: CEA, 0.8%; EVAR, 1.0%; INFRA, 2.6%; SUPRA, 3.1%; and OAAA repair, 4.3% ( P < .001). Predictors of POMI in the all-procedure model included age, operation type, coronary artery disease, congestive heart failure, diabetes, creatinine concentration >1.8 mg/dL, stress test status, and body mass index (AUC, 0.75; 95% confidence interval CI, 0.73-0.76). The all-procedure model demonstrated only minimally reduced accuracy when it was applied to each procedure, with the following AUCs: CEA, 0.65 (95% CI, 0.59-0.70); INFRA, 0.69 (95% CI, 0.64-0.73); EVAR, 0.72 (95% CI, 0.65-0.80); SUPRA, 0.62 (95% CI, 0.52-0.72); and OAAA, 0.63 (95% CI, 0.56-0.70). Procedure-specific models had unique predictors and showed improved prediction compared with the all-procedure model, with the following AUCs: CEA, 0.69 (95% CI, 0.66-0.72); INFRA, 0.75 (95% CI, 0.73-0.78); EVAR, 0.76 (95% CI, 0.73-0.80); and OAAA, 0.72 (95% CI, 0.69-0.77). Bias-corrected AUC (95% CI) from internal validation for the models was as follows: all procedures, 0.75 (0.73-0.76); CEA, 0.68 (0.65-0.71); INFRA, 0.74 (0.72-0.76); EVAR, 0.73 (0.70-0.78); and OAAA repair, 0.68 (0.65-0.73). Conclusions The VQI CRI is a useful and valid clinical decision-making tool to predict POMI after vascular surgery. Procedure-specific models improve accuracy when they include unique risk factors.
Outcomes for intact abdominal aortic aneurysm (AAA) repair vary over time and by healthcare system, country, and surgeon. The aim of this study was to analyse peri-operative mortality for intact AAA ...repair in 11 countries over time and compare outcomes by gender, age, and geographical location.
Prospective data on primary repair of intact AAA were collected from 11 countries through the International Consortium of Vascular Registries (ICVR) and analysed for two time periods, 2010 – 2013 and 2014 – 2016. The primary outcome was peri-operative mortality after endovascular aneurysm repair (EVAR) and open surgical repair (OSR). Multivariable logistic regression models were used to adjust for differences in patient characteristics.
A total of 103 715 patients were included. The percentage of patients undergoing EVAR increased from 63.6% to 71.2% (p < .001) over the study period. This proportion varied by country from 35% in Hungary to 81% in the United States. Overall peri-operative mortality decreased from 2.1% to 1.6 % (p < .001). Mortality also declined significantly over time for both OSR 4.2% to 3.6 % (p = .002) and EVAR 1.0% to 0.7% (p = .002). Mortality was significantly higher for female than male patients (3.0% vs. 1.6% p < .001). The percentage of patients > 80 years old undergoing AAA repair remained constant at 23.6% (p = .91). Peri-operative mortality was higher for patients > 80 years than for those < 80 years old (2.7% vs. 1.6% p < .001). Forty-six per cent (n = 275) of all EVAR deaths occurred in the over 80s.
The proportion of AAA repairs performed using EVAR has increased over time. Peri-operative mortality continues to decline for both OSR and EVAR. Outcomes however were significantly worse for both women and those aged over 80, so efforts should be focused on these patient groups to further reduce elective AAA mortality rates.
The correlation between center volume and elective abdominal aortic aneurysm (AAA) repair outcomes is well established; however, these effects for either endovascular aneurysm repair (EVAR) or open ...aneurysm repair (OAR) of ruptured AAA (rAAA) remains unclear. Notably, the capacity to either avert or manage complications associated with postoperative mortality is an important cause of outcome disparities after elective procedures; however, there is a paucity of data surrounding nonelective presentations. Therefore, the purpose of this analysis was to describe the association between annual center volume, complications, and failure to rescue (FtR) after EVAR and OAR of rAAA.
All consecutive endovascular and open rAAA repairs from 2010 to 2020 in the Vascular Quality Initiative were examined. Annual center volume (procedures/year per center) was grouped into quartiles: EVAR-Q1 (<14), 3.4%; Q2 (14-23), 12.8%; Q3 (24-37), 24.7%; and Q4 (>38), 59.1%; OAR-Q1 (<3), 5.4%; Q2 (4-6), 12.8%; Q3 (7-10), 22.7%; and Q4 (>10), 59.1%. The primary end point was FtR, defined as in-hospital death after experiencing one of six major complications (cardiac, renal, respiratory, stroke, bleeding, colonic ischemia). Risk-adjusted analyses for intergroup comparisons were completed using multivariable logistic regression.
The unadjusted in-hospital death rate was 16.5% and 28.9% for EVAR and OAR, respectively. Complications occurred in 45% of EVAR (n = 1439/3188) and 70% of OAR (n = 1366/1961) patients with corresponding FtR rates of 14% (EVAR) and 26% (OAR). For OAR, Q4-centers had a 43% lower FtR risk (odds ratio OR, 0.57; 95% confidence interval CI, 0.4-0.9; P = .017) compared with Q1 centers. Centers performing fewer than five OARs/year had a 43% lower risk (OR, 0.57; 95% CI, 0.4-0.7; P < .001) of FtR and this decreased 4% for each additional five procedures performed annually (95% CI, 0.93-0.991; P = .013). However, there was no significant relationship between center volume and FtR after EVAR. The risk of FtR was strongly associated with a greater number of complications for both procedures (OR multiplied by 6.5 for EVAR and 1.5 for OAR for each additional complication; P < .0001). Among OAR patients with a single recorded complication, return to the operating room for bleeding had highest risk of in-hospital mortality (OR, 4.1; 95% CI, 1.1-4.8; P = .034), whereas no specific type of complication increased FtR risk after EVAR.
FtR occurs commonly after EVAR and OAR of rAAA within Vascular Quality Initiative centers. Importantly, increasing center volume was associated with decreased FtR risk after OAR, but not EVAR. Complication pattern and frequency predicted FtR after either repair strategy. For stable patients, especially those deemed anatomically ineligible for EVAR, these findings emphasize the need to improve the coordination of regional referral networks that centralize rAAAs to high-volume centers. Moreover, hospitals that treat rAAA should invest in resources that develop protocols targeting specific complications to mitigate risk of preventable postoperative death.
Objective Spinal cord ischemia (SCI) is a devastating but potentially preventable complication of thoracic endovascular aortic repair (TEVAR). The purpose of this analysis was to determine what ...factors predict SCI after TEVAR. Methods All TEVAR procedures at a single institution were reviewed for patient characteristics, prior aortic repair history, aortic centerline of flow analysis, and procedural characteristics. SCI was defined as any lower extremity neurologic deficit that was not attributable to an intracranial process or peripheral neuropathy. Forty-three patient and procedural variables were evaluated individually for association with SCI. Those with the strongest relationships to SCI ( P < .1) were included in a multivariable logistic regression model, and a stepwise variable elimination algorithm was bootstrapped to derive a best subset of predictors from this model. Results From 2002 to 2013, 741 patients underwent TEVAR for various indications, and 68 (9.2%) developed SCI (permanent: n = 38; 5.1%). Because of the lack of adequate imaging for centerline analysis, 586 patients (any SCI, n = 43; 7.4%) were subsequently analyzed. Patients experiencing SCI after TEVAR were older (SCI, 72 ± 11 years; no SCI, 65 ± 15 years; P < .0001) and had significantly higher rates of multiple cardiovascular risk factors. The stepwise selection procedure identified five variables as the most important predictors of SCI: age (odds ratio OR multiplies by 1.3 per 10 years; 95% confidence interval CI, 0.9-1.8, P = .06), aortic coverage length (OR multiplies by 1.3 per 5 cm; CI, 1.1-1.6; P = .002), chronic obstructive pulmonary disease (OR, 1.9; CI, 0.9-4.1; P = .1), chronic renal insufficiency (creatinine concentration ≥ 1.6 mg/dL; OR, 1.9; CI, 0.8-4.2; P = .1), and hypertension (defined as chart history or medication; OR, 6.4; CI, 2.6-18; P < .0001). A logistic regression model with just these five covariates had excellent discrimination (area under the receiver operating characteristic curve = .83) and calibration ( χ2 = 9.8; P = .28). Conclusions This analysis generated a simple model that reliably predicts SCI after TEVAR. This clinical tool can assist decision-making about when to proceed with TEVAR, guide discussions about intervention risk, and help determine when maneuvers to mitigate SCI risk should be implemented.
The early survival advantage of endovascular aneurysm repair (EVAR) compared with open repair reverses over time, possibly because of higher rates of reintervention related to endoleaks and aneurysm ...sac expansion. Therefore, we sought to examine the association between sac behavior, endoleaks, reintervention, and long-term survival.
We reviewed all patients undergoing EVAR in the Vascular Quality Initiative between 2003 and 2017 with an imaging study at 1 year postoperatively (±6 months). We defined aneurysm sac changes by Society for Vascular Surgery guidelines (change ≥5 mm) and determined independent predictors of sac behavior, new endoleak, and reintervention using hierarchical logistic regression. We employed Cox regression to examine the association between sac behavior and long-term survival. We performed propensity matching between patients with sac regression and those with failure to regress as a secondary analysis.
Of 30,074 EVAR patients, 14,817 (49%) had a 1-year imaging study and were included in this study. At 1 year, 40% of sacs regressed, 35% remained stable, and 25% expanded. Factors independently associated with sac expansion were age (by decade: odds ratio OR, 1.07; 95% confidence interval CI, 1.01-1.13; P = .02), appearance of new endoleak (OR, 1.23; 95% CI, 1.10-1.37; P = .001), smaller aortic diameter (diameter <5 cm: OR, 1.37; 95% CI, 1.21-1.55; P < .001), anemia (OR, 1.47; 95% CI, 1.20-1.80; P < .001), rupture (OR, 1.33; 95% CI, 1.07-1.65; P = .01), and chronic kidney disease (OR, 1.15; 95% CI, 1.05-1.25; P < .01), whereas former smoking (OR, 0.86; 95% CI, 0.76- 0.96; P < .01), cerebrovascular disease (OR, 0.82; 95% CI, 0.67-0.99; P = .04), and statin therapy at discharge (OR, 0.83; 95% CI, 0.75-0.91; P < .001) were associated with lower risk of expansion. Both sac expansion (OR, 2.3; 95% CI, 2.0-2.7; P < .001) and a stable sac (OR, 3.1; 95% CI, 2.7-3.5; P < .001) were associated with the development of new endoleaks. Any failure of the aneurysm sac to regress was associated with long-term mortality compared with sac regression (stable sac size: hazard ratio, 1.2; 95% CI, 1.03-1.4; P = .02; sac expansion: hazard ratio, 1.6; 95% CI, 1.3-2.1; P < .001). This association persisted in patients without documented endoleaks and remained robust after accounting for reinterventions and endoleaks seen in follow-up or on completion angiography. In the propensity-matched cohort, patients with failure to regress experienced lower long-term survival (77% at 10 years compared with 82% for patients with sac regression; P = .01).
After EVAR, aneurysm sac behavior is associated with the development of new endoleaks, reintervention, and long-term mortality. Not only sac expansion but any failure of the sac to regress is associated with higher long-term mortality, independent of reinterventions or endoleaks, and may be modified by statin therapy. Further study is needed to establish whether patients with stable sacs could benefit from selective reintervention.
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