***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 
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    Input: Background Aortic dissection still has a poor prognosis despite progress in therapy . Therefore , this prospect i ve follow-up study was design ed to determine whether the degree of communication between true and false lumen in relation to the type of dissection , analyzed by transesophageal echocardiography , influences the risk after initiation of medical or surgical therapy . Methods and Results In eight centers , 168 patients ( 124 men and 44 women ) of age range of 23 - 84 years with proven aortic dissection were examined by transesophageal echocardiography in the acute phase , after start of medical and /or surgical therapy  , and during follow-up ( 0–65 months ; mean , 10 months ) . Analyses were performed prospect ively according to a detailed study protocol . Patients were subdivided by transesophageal echocardiography according to a modified DeBakey classification . Type I aortic dissection was found in 35 % , typeII aortic dissection in 17 % , and typem aortic dissection in 48 % . Preoperative mortality was 3 % , 7 % , and 2 % , and survival rates were 52 % , 69 % , and 70 % , respectively . Typem aortic dissection could be subdivided into those with communication and ante grade dissection ( ca ) ( 50 % ) , with communication and retro grade dissection limited to the descending aorta ( cr desc ) ( 10 % ) , with dissection extended to the aortic arch and ascending aorta ( cr asc ) ( 27 % ) , and withnoncommunicating ( nc ) aortic dissection ( 13 % ) . An open false lumen with no thrombus formation was present in typesI , II , m ca and mcr asc aortic dissection in 17 % 21 % , 39 % , and 27 % respectively , although it was most pronounced in typesm nc and mcr desc ( 75 % and 78 % ) . During follow-up in patients who survived , thrombus was demonstrated in the false lumen in 80 % of type I aortic dissection and 81 % of typesm ca and m cr asc . Open false lumen was seen in type H aortic dissection in 18 % . Spontaneous healing was found in 4 % with type H and 4 % with typem aortic dissection ( mainly in patients with typem nc aortic dissection ) . Patients with fluid extravasation , pleural effusion , pericardial tamponade , and periaortic effusion as well as mediastinal hematoma had a mortality of 52 % . Reoperations were necessary in 12 - 29 % , with thehighest rate in patients with typem ca aortic dissection . Survival for patients with types M nc and m cr desc aortic dissection was higher than those with types I , II , m ca , and m cr asc . Conclusions Preoperative mortality appears to be reduced by transesophageal echocardiography , allowing rapid initiation of treatment . Intraoperative and postoperative mortality in aortic dissection remains high . Risk factors are fluid extravasation and an open false lumen with high communication . Thrombus formation in the false lumen can be regarded as a good prognostic sign . Surgery appears tobe only a first step in the treatment of aortic dissection . Second surgery or closure of entry sites based on intraoperative echocardiography may be considered to induce thrombus formation and reduce aortic wall stress INTRODUCTION The aim of this retrospective study was to compare the outcome of thoracic endovascular aortic repair ( TEVAR ) to that of medical therapy in patients with acute type B aortic dissection ( TBD ) . MATERIAL S AND METHODS From July 1996 to April 2008 , 88 patients presenting with acute TBD underwent either TEVAR ( group A , n=38 ) or medical therapy ( group B , n=50 ) . Indications for TEVAR were intractable pain , aortic branch compromise result ing in end-organ ischemia , rapid aortic dilatation and rupture . Follow-up was performed postinterventionally , at 3 , 6 and 12 months and yearly thereafter and included clinical examinations and computed tomography ( CT ) , as well as  aortic diameter measurements  and assessment of thrombosis . RESULTS Mean follow-up was 33 months in group A and 36 months in group B. The overall mortality rate was 23.7 % in group A and 24 % in group B , where 4 patients died of late aortic rupture . In group A , complications included 9 endoleaks and 4 retro grade type A dissections , 3 patients were converted to open surgery and 2 needed secondary intervention . None of the patients developed paraplegia . In group B , 4 patients were converted to open surgery and 2 to TEVAR . The maximal aortic diameter increased in both groups . Regarding the extent of thrombosis , our analyses showed slightly better overall results after TEVAR , but they also showed a tendency towards approximation between the two groups during follow-up . CONCLUSION TEVAR is a feasible treatment option in acute TBD . However , several serious complications may occur during and after TEVAR and it should therefore be reserved to patients with life-threatening symptoms PURPOSE This study describes the design of an ongoing r and omized trial initiated to compare the 2-year outcome of uncomplicated type B aortic dissection when treated by endovascular implantation of a Medtronic Talent stent graft adjunctive to best medical treatment versus best medical treatment alone . METHODS Patients older than 18 years with type B aortic dissection as diagnosed by computed tomography or magnetic resonance angiography are r and omized to either a thoracic aortic endoprosthesis and antihypertensive treatment , called " stent grafting , " or a tailored antihypertensive treatment , called " medical treatment . "  Only patients in a clinical ly stable condition and without spontaneous thrombosis of the false lumen after 14 days of the index dissection are considered eligible for study inclusion . RESULTS Primary outcome measure is all-cause mortality . Secondary outcome variables include conversion to stent and /or surgery , induced thrombosis of the false lumen , cardiovascular morbidity , aortic expansion ( > 5 mm/y of maximum diameter including true and false lumina ) , quality of life , and length of intensive care unit and hospital stay . The study design calls for 136 patients to be r and omized and monitored for 24 months . CONCLUSIONS The INSTEAD trial is the first r and omized trial investigating the role of endoluminal treatment of uncomplicated type B aortic dissection . By the end of December 2004 , 125 patients were r and omized , accounting for 92 % of the target . Final results of the INSTEAD trial should be available in 2006 Background — Thoracic endovascular aortic repair ( TEVAR ) represents a novel concept for type B aortic dissection . Although life-saving in acute emergencies , outcomes and survival of TEVAR in stable dissection are unknown . Methods and Results — One hundred forty patients in stable clinical condition at least 2 weeks after index dissection were r and omly subjected to elective stent-graft placement in addition to optimal medical therapy ( n=72 ) or to optimal medical therapy alone ( n=68 )  with surveillance ( arterial pressure according to World Health Organization guidelines ≤120/80 mm Hg ) . The primary end point was all-cause death at 2 years , whereas aorta-related death , progression ( with need for conversion or additional endovascular or open surgery ) , and aortic remodeling were secondary end points . There was no difference in all-cause deaths , with a 2-year cumulative survival rate of 95.6±2.5 % with optimal medical therapy versus 88.9±3.7 % with TEVAR ( P=0.15 ) ; the trial , however , turned out to be underpowered . Moreover , the aorta-related death rate was not different ( P=0.44 ) , and the risk for the combined end point of aorta-related death ( rupture ) and progression ( including conversion or additional endovascular or open surgery ) was similar ( P=0.65 ) . Three neurological adverse events occurred in the TEVAR group ( 1 paraplegia , 1 stroke , and 1 transient paraparesis ) , versus 1 case of paraparesis with medical treatment . Finally , aortic remodeling ( with true-lumen recovery and thoracic false-lumen thrombosis ) occurred in 91.3 % of patients with TEVAR versus 19.4 % of those who received medical treatment ( P<0.001 ) , which suggests ongoing aortic remodeling . Conclusions — In the first r and omized study on elective stent-graft placement in survivors of uncomplicated type B aortic dissection , TEVAR failed to improve 2-year survival and adverse event rates despite favorable aortic remodeling . Clinical Trial Registration — URL : http://www . clinical trials.gov . Unique identifier : NCT00525356 Acute dissection of the descending thoracic aorta carries a 30-day mortality of around 10 % with best medical treatment ( BMT ) . In addition , about 25 % will develop an aneurysm during the following 4 - 5 years . This is the first ever r and omised trial on acute dissections comparing BMT with BMT and stent grafting of the proximal tear in patients having an uncomplicated acute dissection of the descending aorta . The commonly used temporal definition of acute dissection being within 14 days of onset of symptoms is applied . A total of 61 patients will be r and omised and followed at regular intervals ( 1 , 3 , 6 , 12 , 18 , 24 , 30 and 36 months ) after acute dissection . Thrombosis of the false lumen , aortic enlargement and rupture are the primary end points . The study will examine whether aortic remodelling occurs after stent grafting in acute type B dissections , and its effect on aneurysm formation , rupture and re-intervention BACKGROUND The treatment of thoracic aortic dissection is guided by prognostic and anatomical information . Proximal dissection requires surgery , but the appropriate treatment of distal thoracic aortic dissection has not been determined , because surgery has failed to improve the prognosis . METHODS We prospect ively evaluated the safety and efficacy of elective transluminal endovascular stent-graft insertion in 12 consecutive patients with descending ( type B ) aortic dissection and compared the results with surgery in 12 matched controls . In all 24 patients , aortic dissection was diagnosed by magnetic resonance angiography . In each group , the dissection involved the aortic arch in 3 patients and the descending thoracic aorta in all 12 patients . With the patient under general anesthesia , either surgical resection was undertaken or a custom- design ed endovascular stent-graft was placed by unilateral arteriotomy . RESULTS Stent-graft placement result ed in no morbidity or mortality , whereas surgery for type B dissection was associated with four deaths ( 33 percent , P=0.09 ) and five serious adverse events ( 42 percent , P=0.04 ) within 12 months . Transluminal placement of the stent-graft prosthesis was successful in all patients , with no leakage ; full expansion of the stents was ensured by balloon inflation at 2 to 3 atm . Sealing of the entry tear was monitored during the procedure by transesophageal ultrasonography and angiography , and thrombosis of the false lumen was confirmed in all 12 patients after a mean of three months by magnetic resonance imaging . There were no deaths or instances of paraplegia , stroke , embolization , side-branch occlusion , or infection in the stent-graft group ; nine patients had postimplantation syndrome , with transient elevation of C-reactive protein levels and body temperature plus mild leukocytosis . All the patients who received stent-grafts recovered , as did seven patients who underwent surgery for type B dissection ( 58 percent ) ( P=0.04 ) . CONCLUSIONS These preliminary observations suggest that elective , nonsurgical insertion of an endovascular stent-graft is safe and efficacious in selected patients who have thoracic aortic dissection and for whom surgery is indicated . Endoluminal repair may be useful for interventional reconstruction of thoracic aortic dissection OBJECTIVE Endovascular stent grafting represents a novel concept for type B aortic dissection both in the acute and subacute/chronic setting , with an unknown effect on outcomes . METHODS In a prospect i ve trial 140 patients with stable type B dissection were r and omly subjected to elective stent-graft placement in addition to optimal medical therapy ( n = 72 )  or to optimal medical therapy  ( n = 68 ) with surveillance ( arterial pressure according to World Health Organization guidelines ≤ 120/80 mm Hg ) . The primary end point was 1-year all-cause mortality , whereas aorta-related mortality , progression ( with need for conversion or additional endovascular or open surgical intervention ) , and aortic remodeling were secondary end points . RESULTS There was no difference in all-cause mortality : cumulative survival was 97.0 % ± 3.4 % with optimal medical therapy versus 91.3 % ± 2.1 % with thoracic endovascular aortic repair ( P = .16 ) . Moreover , aorta-related mortality was not different ( P = .42 ) , and the risk for the combined end point of aorta-related death ( rupture ) and progression ( 
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However , the data on the anatomic remodeling of dissected aortas observed after TEVAR + OMT is encouraging and future studies should follow up cases for at least five years to see if early endovascular interventions , even in stable initially uncomplicated type B patients , are of long-term benefit