***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 Many patients have symptoms suggestive of coronary artery disease ( CAD ) and are often evaluated with the use of diagnostic testing , although there are limited data from r and omized trials to guide care . METHODS We r and omly assigned 10,003 symptomatic patients to a strategy of initial anatomical testing with the use of coronary computed tomographic angiography ( CTA ) or to functional testing ( exercise electrocardiography , nuclear stress testing , or stress echocardiography ) . The composite primary end point was death , myocardial infa rct ion , hospitalization for unstable angina , or major procedural complication . Secondary end points included invasive cardiac catheterization that did not show obstructive CAD and radiation exposure . RESULTS The mean age of the patients was 60.8±8.3 years , 52.7 % were women , and 87.7 % had chest pain or dyspnea on exertion . The mean pretest likelihood of obstructive CAD was 53.3±21.4 % . Over a median follow-up period of 25 months , a primary end-point event occurred in 164 of 4996 patients in the CTA group ( 3.3 % ) and in 151 of 5007 ( 3.0 % ) in the functional-testing group ( adjusted hazard ratio , 1.04 ; 95 % confidence interval , 0.83 to 1.29 ; P=0.75 ) . CTA was associated with fewer catheterizations showing no obstructive CAD than was functional testing ( 3.4 % vs. 4.3 % , P=0.02 ) , although more patients in the CTA group underwent catheterization within 90 days after r and omization ( 12.2 % vs. 8.1 % ) . The median cumulative radiation exposure per patient was lower in the CTA group than in the functional-testing group ( 10.0 mSv vs. 11.3 mSv ) , but 32.6 % of the patients in the functional-testing group had no exposure , so the overall exposure was higher in the CTA group ( mean , 12.0 mSv vs. 10.1 mSv ; P<0.001 ) . CONCLUSIONS In symptomatic patients with suspected CAD who required noninvasive testing , a strategy of initial CTA , as compared with functional testing , did not improve clinical outcomes over a median follow-up of 2 years . ( Funded by the National Heart , Lung , and Blood Institute ; PROMISE Clinical Trials.gov number , NCT01174550 . ) OBJECTIVES The purpose of this study was to compare the efficiency , cost , and safety of a diagnostic strategy employing early coronary computed tomographic angiography ( CCTA ) to a strategy employing rest-stress myocardial perfusion imaging ( MPI ) in the evaluation of acute low-risk chest pain . BACKGROUND In the United States , > 8 million patients require emergency department evaluation for acute chest pain annually at an estimated diagnostic cost of > $ 10 billion . METHODS This multicenter , r and omized clinical trial in 16 emergency departments ran between June 2007 and November 2008 . Patients were r and omly allocated to CCTA ( n = 361 ) or MPI ( n = 338 ) as the index noninvasive test . The primary outcome was time to diagnosis ; the secondary outcomes were emergency department costs of care and safety , defined as freedom from major adverse cardiac events in patients with normal index tests , including 6-month follow-up . RESULTS The CCTA result ed in a 54 % reduction in time to diagnosis compared with MPI ( median 2.9 h [ 25th to 75th percentile : 2.1 to 4.0 h ] vs. 6.3 h [ 25th to 75th percentile : 4.2 to 19.0 h ] , p < 0.0001 ) . Costs of care were 38 % lower compared with st and ard ( median $ 2,137 [ 25th to 75th percentile : $ 1,660 to $ 3,077 ] vs. $ 3,458 [ 25th to 75th percentile : $ 2,900 to $ 4,297 ] , p < 0.0001 ) . The diagnostic strategies had no difference in major adverse cardiac events after normal index testing ( 0.8 % in the CCTA arm vs. 0.4 % in the MPI arm , p = 0.29 ) . CONCLUSIONS In emergency department acute , low-risk chest pain patients , the use of CCTA results in more rapid and cost-efficient safe diagnosis than rest-stress MPI . Further studies comparing CCTA to other diagnostic strategies are needed to optimize evaluation of specific patient subsets . ( Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment [ CT-STAT ] ; NCT00468325 ) STUDY OBJECTIVE Three large , multicenter , r and omized , clinical trials have shown that coronary computed tomography ( CT ) angiography allows efficient evaluation and safe discharge of patients with low- to intermediate-risk chest pain who present to the emergency department ( ED ) . We report 1-year event rates and re source use from the American College of Radiology Imaging Network-Pennsylvania 4005 multicenter trial . METHODS Patients with low- to intermediate-risk chest pain and presenting to the ED were r and omized in a 2:1 ratio to a coronary CT angiography care pathway or traditional care .  Subjects were contacted by telephone at least 1 year after ED presentation . Medical record review was performed for all cardiac hospitalizations , procedures and diagnostic tests , and adverse cardiac events . Our main outcome was the composite of cardiac death and myocardial infa rct ion within 1 year . The secondary outcome was re source use . RESULTS One thous and three hundred sixty-eight patients enrolled and 1,285 ( 94 % ) had direct participant or proxy contact at 1 year . All others had record review or death index search . From index presentation through 1 year , there was no difference between patients in the coronary CT angiography arm versus traditional care with respect to major adverse cardiac event ( 1.4 % versus 1.1 % ; difference 0.3 % ; 95 % CI -5.5 % to 6.0 % ) . From hospital discharge through 1 year , there was also no difference in ED revisits ( 36 % versus 38 % ; difference -2.1 % ; 95 % CI -7.9 % to 3.7 % ) , hospital admissions ( 16 % versus 17 % ; difference -0.9 % ; 95 % CI -6.7 % to 4.9 % ) , or subsequent cardiac testing ( 13 % versus 13 % ; difference -0.4 % ; 95 % CI -6.2 % to 5.5 % ) . One of 640 subjects with a negative coronary CT angiography result had a major adverse cardiac event within 1 year of presentation ( 0.16 % ; 95 % CI 0.004 % to 0.87 % ) . CONCLUSION A coronary CT angiography-based strategy for evaluation of patients with low- to intermediate-risk chest pain who present to the ED does not result in increased re source use during 1 year . A negative coronary CT angiography result is associated with a less than 1 % major adverse cardiac event rate during the first year after testing OBJECTIVES This study sought to compare the safety , diagnostic efficacy , and efficiency of multi-slice computed tomography ( MSCT ) with st and ard diagnostic evaluation of low-risk acute chest pain patients . BACKGROUND Over 1 million patients have emergency center evaluations for acute chest pain annually , at an estimated diagnostic cost of over $ 10 billion . Multi-slice computed tomography has a high negative predictive value for exclusion of coronary artery stenoses . METHODS We r and omized patients to MSCT ( n = 99 ) versus SOC ( n = 98 ) protocol s. The MSCT patients with minimal disease were discharged ; those with stenosis > 70 % underwent catheterization , whereas cases with intermediate lesions or non-diagnostic scans underwent stress testing . Outcomes included : safety ( freedom from major adverse events over 6 months ) , diagnostic efficacy ( clinical ly correct and definitive diagnosis ) , as well as time and cost of care . RESULTS Both approaches were completely ( 100 % ) safe . The MSCT alone immediately excluded or identified coronary disease as the source of chest pain in 75 % of patients , including 67 with normal coronary arteries and 8 with severe disease referred for invasive evaluation . The remaining 25 % of patients required stress testing , owing to intermediate severity lesions or non-diagnostic scans . During the index visit , MSCT evaluation reduced diagnostic time compared with SOC ( 3.4 h vs. 15.0 h , p < 0.001 ) and lowered costs ( 1,586 dollars vs. 1,872 dollars , p < 0.001 ) . Importantly , MSCT patients required fewer repeat evaluations for recurrent chest pain  ( MSCT , 2 of 99 ( 2.0 % ) patients vs. SOC , 7 of 99 ( 7 % ) patients ; p = 0.10 ) . CONCLUSIONS Multi-slice computed tomographic coronary angiography can definitively establish or exclude coronary disease as the cause of chest pain . However , inability to determine the physiological significance of intermediate severity coronary lesions and cases with inadequate image quality are present limitations . ( Study of Coronary Artery Computed Tomography to Diagnose Emergency Chest Pain CR ; http:// clinical trials.gov/ct/show/NCT00273832?order=1 ; NCT00273832 ) BACKGROUND It is unclear whether an evaluation incorporating coronary computed tomographic angiography ( CCTA ) is more effective than st and ard evaluation in the emergency department in patients with symptoms suggestive of acute coronary syndromes . METHODS In this multicenter trial , we r and omly assigned patients 40 to 74 years of age with symptoms suggestive of acute coronary syndromes but without ischemic electrocardiographic changes or an initial positive troponin test to early CCTA or to st and ard evaluation in the emergency department on weekdays during daylight hours between April 2010 and January 2012 . The primary end point was length of stay in the hospital . Secondary end points included rates of discharge from the emergency department , major adverse cardiovascular events at 28 days , and cumulative costs . Safety end points were undetected acute coronary syndromes . RESULTS The rate of acute coronary syndromes  among 1000 patients with a mean ( ±SD ) age of 54±8 years ( 47 % women ) was 8 % . After early CCTA , as compared with st and ard evaluation  , the mean length of stay in the hospital was reduced by 7.6 hours ( P<0.001 ) and more patients were discharged directly from the emergency department ( 47 % vs. 12 % , P<0.001 ) . There were no undetected acute coronary syndromes and no significant differences in major adverse cardiovascular events at 28 days . After CCTA , there was more downstream testing and higher radiation exposure . The cumulative mean cost of care was similar in the CCTA group and the st and ard-evaluation group ( $ 4,289 and $ 4,060 , respectively ; P=0.65 ) . CONCLUSIONS In patients in the emergency department with symptoms suggestive of acute coronary syndromes , incorporating CCTA into a triage strategy improved the efficiency of clinical decision making , as compared with a st and ard evaluation in the emergency department , but it result ed in an increase in downstream testing and radiation exposure with no decrease in the overall costs of care . ( Funded by the National Heart , Lung , and Blood Institute ; ROMICAT-II Clinical Trials.gov number , NCT01084239 . ) OBJECTIVES In patients admitted on suspicion of acute coronary syndrome , with normal electrocardiogram and troponines , we evaluated the clinical impact of a Coronary CT angiography (CCTA)- strategy on referral rate for  invasive coronary angiography ( ICA ) , detection of significant coronary stenoses ( positive predictive value [ PPV ] ) and subsequent revascularisations , as compared to a function-based strategy ( st and ard care ) . Secondarily we assessed intermediate term clinical events . METHODS AND RESULTS We r and omised 600 patients to a CCTA-guided strategy ( 299 patients ) or st and ard care ( 301 patients ) . In the CCTA-guided group referral for ICA required a coronary stenosis > 70 % or > 50 % in the left main , and for intermediate stenoses ( 50 - 70 % ) , a stress test was used . A significant stenosis on ICA was defined as a stenosis ≥70 % or reduced FFR ≤0.75 in intermediate stenoses ( 50 - 70 % ) . Referral rate for ICA was 17 % with CCTA vs. 12 % with st and ard care ( p=0.1 ) . ICA confirmed significant coronary artery stenoses in 12 % vs. 4 % ( p=0.001 ) , and 10 % vs. 4 % were subsequently revascularised ( p=0.005 ) . PPV for the detection of significant stenoses was 71 % with CCTA vs 36 % with st and ard care ( p=0.001 ) . Clinical events ( cardiac death , myocardial infa rct ion , unstable 
    Output:
    
Consequently , compared with conventional strategy , CCTA seemed not to improve clinical outcomes for patients with low-to-intermediate risk chest pain