***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Major vessel stenoses are currently successfully treated with stent implantation . Recently , new cobalt-chromium stents ( And rastents XL and XXL , And ramed , Germany ) have been introduced into clinical practice . This alloy combines high biocompatibility with radial strength and flexibility . AIM To present our experience with the use of And rastents XL and XXL for the dilatation of stenosed pulmonary arteries , coa rct ation of the aorta ( CoA ) , and a stenosed superior vena cava ( SVC ) . METHODS The study group included 24 patients treated with 26 And rastents .  In 7 patients aged 23.3 ( range 18 - 27 ) years , with the mean body weight of 64.7 ( range 50 - 77 ) kg , prestenting of a calcified pulmonary homograft was performed using 9 And rastents XL or XXL ( length of 30 , 39 , or 48 mm ) before the Melody valve implantation . In one patient with a long and stiff stenosis , 3 stents were necessary . In 12 patients with native CoA aged 30.1 ( range 9 - 55 ) years , with the mean body weight of 60 ( range 25 - 105 ) kg , twelve And rastents XL or XXL ( length of 30 , 39 , or 48 mm ) were implanted . In 4 patients with the right or left pulmonary artery stenosis close to the bifurcation ( age 8.5 [ range 6 - 10 ] years , body weight 27.3 [ range 17 - 33 ] kg ) , 4 And rastents 30 XL were implanted . In one child ( age 7.5 years , body weight 21.7 kg ) with a iatrogenic SVC stenosis ( after 2 venous cannulations necessary for 2 surgical corrections of his double-outlet right ventricle ) , the stenosed site was dilated using And rastent 21 XL . RESULTS All procedures were performed successfully . No stent fractures were observed during the follow-up . The mean pressure gradient was reduced from 42.4 to 18 mm Hg ( RVOT ) in patients who underwent And rastent and Melody valve implantation , from 54.1 to 13.2 mm Hg in patients with CoA , and from 49 to 21.7 mm Hg in patients with pulmonary artery stenosis . No aneurysm formation , stent migration , or rupture of the treated vessel during stent implantation were observed in any patient . The mean fluoroscopy time during stent implanatation was 6.6 min in CoA , 8.8 min in pulmonary artery stenosis , 24.8 min during implantation of Melody valve ( with prestenting of RVOT with And rastents ) and 17.6 min during SVC dilation . Procedural outcomes ( evaluated using noninvasive methods ) remained favourable during the follow-up ( 0.5 - 21 months ) , with no complications observed . CONCLUSIONS Implantation of And rastents XL or XXL is a very good therapeutic option in the treatment of major vessel stenoses Objective : To determine the safety , feasibility and effectiveness of stent expansion of hypoplastic aortic segments with pressure gradients in patients with arterial hypertension . Design : Non-r and omised prospect i ve clinical trial . Setting : Tertiary referral centre , congenital cardiac unit . Patient selection : 20 consecutive patients ( median age 14.5 years , range 11.6–38.8 years ) with arterial hypertension and a hypoplastic segment of the aorta . Seventeen patients had successful previous arch interventions in a coa rct ation site . Interventions : Stent deployment in hypoplastic arch segments . Main outcome measures : Gradient across the aortic arch ; complications early and during follow up ; residual hypertension . Results : 23 stents were deployed : 13 in the cross and 10 in the isthmus . The mean gradient across the aortic arch decreased from 16 ( SD 6 ) ( median 17 ) to 3 ( 4 ) ( median 1 ) mm Hg ( p < 0.001 ) . In a few patients a mild gradient persisted just distal to the left carotid artery due to residual orificial narrowing or acute angulation . No complications occurred during or after the procedure . During follow up of 2.2 years ( range 0.2–4.8 years ) arterial hypertension resolved in 10 patients and 10 required residual drug treatment with better control of blood pressures . Conclusions : Pressure loss due to residual hypoplastic aortic segments can be treated effectively and safely with stent expansion . Some patients remain mildly hypertensive and require additional drug treatment Objective : To compare results of dilatation of native coa rct ation of the aorta with and without stent implantation . Design : Open , observational , non-r and omised study . Patients : 54 consecutive adult patients : 32 with balloon angioplasty alone ( group 1 ) and 22 with stent placement ( group 2 ) . Interventions : Balloon dilatation from 1995 to 1997 ; dilatation with Palmaz stent placement from 1997 to 1999 . Main outcome measures : The primary end point was a composite index of failure including heart related death , a residual gradient of > 20 mm Hg , the need of reintervention , and aneurysm formation . Results : Peak systolic gradient ( mean ( SD ) ) was reduced both in group 1 ( from 63.3 ( 22.8 ) to 10.7 ( 10.8 ) mm Hg , p < 0.001 ) and group 2 ( from 63.9 ( 20.8 ) to 2.7 ( 4.3 ) mm Hg , p < 0.001 ) , but Δ change was significantly greater in group 2 . A residual gradient of > 10 mm Hg was shown to be the best cut off point to separate risk groups , representing a hazard ratio ( HR ) of 9.59 compared with a residual gradient of ≤ 10 mm Hg ( 95 % confidence interval ( CI ) 1.92 to 47.8 ) . From multivariate Cox regression analysis , the only risk marker was the residual gradient ( HR 8.9 , 95 % CI 1.2 to 63.0 ) . The type of the coa rct ation and the use of stent were the factors associated with a residual gradient of ≤ 10 mm Hg . Conclusions : Mid term outcome in adult patients with native aortic coa rct ation receiving percutaneous treatment is strongly related to the immediate residual gradient . When treating these cases , efforts should be made to obtain gradients under 10 mm Hg , either by angioplasty alone or by placing a stent . Patients with discrete aortic coa rct ation have similar mid term results when the immediate residual gradient is ≤ 10 mm Hg despite the implantation of a stent . To achieve these gradients , patients with hypoplastic isthmus or tubular coa rct ation should be treated with primary stenting . Further studies including exercise tests and non-invasive imaging are still needed before definitive conclusions can be drawn Purpose : To prospect ively assess the efficacy of self-exp and ing nitinol aortic stents in the treatment of coa rct ation of the aorta ( CoA ) . Methods : Between July 2005 and July 2008 , 21 patients ( 14 men ; mean age 19.2±5.5 years , range 11–34 ) with CoA were treated with self-exp and ing Sinus-Aorta stents . The predilation balloon was selected to be < 5 times the stenosis diameter . The stent diameter was selected to be 20 % to 30 % greater than the diameter of the undiseased aorta at the level of the diaphragm . Results : All procedures were successfully performed without any major complications . Predilation ( mean balloon diameter 12.3 mm ) and postdilation ( mean balloon diameter 15.4 mm ) were performed in 12 and 14 procedures , respectively . The mean diameter of the stents was 21.6±2.3 mm ( range 18–26 ) . The mean peak transcoa rct ation pressure gradient decreased from 57.4±19.5 mmHg ( range 30–100 ) before the procedure to 1.2±2.2 mmHg ( range 0–7 ; p<0.001 ) . Cephalad stent dislodgement with the first-generation device occurred in 3 of 12 patients ; 2 were treated with a second stent overlapping the first , and the third received 3 overlapped stents after the second stent migrated distally . No stent dislodgement occurred in the subsequent 9 patients treated with longer second-generation stents with anti-jump markers . None of the patients had dissection , arterial rupture , or other complications . On follow-up , 1 ( 5 % ) patient had recoa rct ation and minor stent migration after 18 months ; another stent was deployed successfully . No evidence of aneurysm formation was seen in 7 patients undergoing arch imaging . Conclusion : CoA can be successfully and safely managed with self-exp and ing nitinol aortic stents without aortic wall complications . Stent malpositioning can be overcome using oversized stents with anti-jump markers BACKGROUND Balloon angioplasty for native coa rct ation of the aorta ( CoA ) in adults , though promising , is sometimes limited by significant residual gradient ( > 20 mm Hg ) . Few studies available have reported on use of balloon-exp and able stents in such a situation . We evaluated the use of self- and balloon-exp and able stents in patients with suboptimal response to balloon angioplasty ( BA ) . METHODS Twenty-one hypertensive patients ( age , 18 to 61 years ; mean , 28.6 + /- 11.2 years ) with native CoA and in whom results of BA were suboptimal ( ie , residual peak systolic gradient [ PSG ] > 20 mm Hg ) underwent stent implantation . Balloon-exp and able Palmaz stents were implanted in 5 patients ( group A ) and self-exp and able nitinol aortic stents in the remaining 16 patients ( group B ) . RESULTS In group A , PSG decreased from 62.8 + /- 10.6 ( 53 to 80 ) mm Hg to 28.1 + /- 6.3 ( 22 to 39 ) mm Hg after BA . Systolic gradient further decreased to 8.3 + /- 3.9 ( 2 to 16 ) mm Hg ( P < .001 ) after implantation of the balloon-exp and able Palmaz stent . In group B , PSG decreased from 70.2 + /- 24.6 ( 40 to 110 ) mm Hg to 28.4 + /- 9.8 ( 22 to 42 ) mm Hg after BA and further reduced to 9.0 + /- 5.5 ( 4 to 16 ) mm Hg ( P < .001 ) . One of these patients had a nitinol self-exp and able stent implanted after a Palmaz stent embolized immediately after deployment . Nitinol stents were easier to deploy and conformed better to aortic anatomy compared with balloon-exp and able stents . In group A , the diameter of the coa rct ed segment increased from 3.8 + /- 0.8 mm to 13.3 + /- 0.8 mm ( P < .001 ) after stent implantation and in group B it increased from 4.5 + /- 1.1 mm to 14.1 + /- 2.1 mm ( P < .001 ) . There was no significant difference between the two groups in the PSG and diameter of the coa rct ed segment before and after stent implantation . With the exception of one case , in which a Palmaz stent embolized , there was no other complication in our series . On follow-up of 12 to 71 months ( mean , 40.7 + /- 5.8 months ) all the implanted stents remained in their original position and none showed evidence of fracture . Improvement in hypertension was seen in 20 of 21(95.2 % ) of the patients . On recatheterization and angiography 1.2 + /- 0.6 years after implantation in 19 patients , one patient showed an increase in PSG to 27 mm Hg across the nitinol stent and underwent successful redilation . No increase in gradient was seen in other patients . Beneficial late remodeling was seen in 10 of 14(71.4 % ) of patients restudied after implantation of self-exp and able stent . None of the patients showed aneurysm formation . CONCLUSIONS Stent implantation is safe and effective in improving suboptimal results after BA for CoA. Self-exp and able stents were easier to implant , adapted better to the wall of the aorta , and in most patients had similar efficacy in reducing coa rct ation as balloon-exp and able stents OBJECTIVE To investigate the effect of endovascular stenting of aortic coa rct ation  on  biventricular function in adults during intermediate-term follow-up . METHODS 21 patients ( age 34 ( 10 ) years ) were studied prospect ively before and 14 ( 2 ) months after coa rct ation stenting from year 2002 to 2005 .  Biventricular function and blood pressure measurements were made . The post- 
    Output:
    
Stenting is an effective treatment with regard to immediate relief of obstruction and direct lowering effect on blood pressure .
However , there is a lack of evidence regarding late effectiveness concerning durable blood pressure lowering , and limited information on periprocedural and late complications .