***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 In a prospect i ve evaluation of 3950 Los Angeles County firefighters who underwent wellness/fitness examinations , 495 firefighters had abnormal treadmill tests and were referred for cardiology evaluation . Cost of the traditional myocardial perfusion imaging ( MPI ) followed by invasive coronary angiography ( ICA ) was compared with a method incorporating 64-slice multidetector computed tomography ( MDCT ) with coronary calcium score ( CCS ) followed by computed tomographic angiography ( CTA ) and ICA as indicated . OBJECTIVE We compared the costs of 2 methods of predicting coronary artery disease ( CAD ) by ICA among asymptomatic patients with positive treadmill tests . METHODS A decision-analytic framework was used to compare the net direct costs of CAD diagnosis associated with MDCT versus MPI . In the MDCT arm , all received CCS followed by CTA for those with calcium scores>10 and ICA for those with > or = 50 % stenosis on CTA . For the MPI arm , results were estimated from prior years ' experience , in which firefighters with abnormal treadmill results were referred to ICA . RESULTS Of 495 firefighters , 131 ( 26.9 % ) had abnormal CCS and went to CTA ; 40 ( 8.1 % ) had > or = 50 % stenosis on CTA and went to ICA . According to prior years ' experience with MPI , 146 ( 29.5 % ) would have shown abnormalities requiring ICA . Average cost was $ 1376/person for MPI versus $ 503/person for CCS with or without CTA as gatekeeper . All sensitivity analyses showed lower costs for the MDCT pathway compared with MPI . CONCLUSION In this firefighter population , the cost of ICA-confirmed diagnosis of CAD is substantially lower with MDCT as gatekeeper than with MPI BACKGROUND Multidetector computed tomography ( MDCT ) has high diagnostic value for detecting or excluding coronary artery stenosis . We examined performance characteristics of MDCT for diagnosing or excluding an acute coronary syndrome in patients presenting to the emergency department ( ED ) with possible ischemic chest pain and examined relation to clinical outcome during a 15-month follow-up period . METHODS AND RESULTS We prospect ively studied 58 patients ( 56+/-10 years of age , 36 % female ) with chest pain possibly ischemic in origin and no new ECG changes or elevated biomarkers . The patients underwent 64-slice contrast-enhanced MDCT , which showed normal coronary vessels ( no or trivial atheroma ) in 15 patients , nonobstructive plaque in 20 ( MDCT-negative patients ) , and obstructive coronary disease ( > or = 50 % luminal narrowing ) in 23 ( MDCT-positive group ) . By further investigation ( new elevation of cardiac biomarkers , abnormal myocardial perfusion scintigraphy and /or invasive angiography ) , acute coronary syndrome was diagnosed in 20 of the 23 MDCT-positive patients ( ED MDCT sensitivity 100 % [ 20/20 ] , specificity 92 % [ 35/38 ] , positive predictive value 87 % [ 20/23 ] , negative predictive value 100 % [ 35/35 ] ) . During a 15-month follow-up period , no deaths or myocardial infa rct ions occurred in the 35 patients discharged from the ED after initial triage and MDCT findings . One patient underwent late  percutaneous coronary intervention ( late major adverse cardiovascular events rate , 2.8 % ) . Overall , ED MDCT sensitivity for predicting major adverse cardiovascular events ( death , myocardial infa rct ion , or revascularization ) during hospitalization and follow-up was 92 % ( 12/13 ) , specificity was 76 % ( 34/45 ) , positive predictive value was 52 % ( 12/23 ) , and negative predictive value was 97 % ( 34/35 ) . CONCLUSIONS We found that 64-slice cardiac MDCT is a potentially valuable diagnostic tool in ED patients with chest pain of uncertain origin , providing early direct noninvasive visualization of coronary anatomy . ED MDCT had high positive predictive value for diagnosing acute coronary syndrome , whereas a negative MDCT study predicted a low rate of major adverse cardiovascular events and favorable outcome during follow-up CONTEXT Coronary computed tomography angiography ( CCTA ) is a new noninvasive diagnostic test for coronary artery disease ( CAD ) , but its association with subsequent clinical management has not been established . OBJECTIVE To compare utilization and spending associated with functional ( stress testing ) and anatomical ( CCTA ) noninvasive cardiac testing in a Medicare population . DESIGN , SETTING , AND PATIENTS Retrospective , observational cohort study using cl aims data from a 20 % r and om sample of 2005 - 2008 Medicare fee-for-service beneficiaries 66 years or older with no cl aims for CAD in the preceding year , who received nonemergent , noninvasive testing for CAD ( n = 282,830 ) . MAIN OUTCOME MEASURES Cardiac catheterization , coronary revascularization , acute myocardial infa rct ion , all-cause mortality , and total and CAD-related Medicare spending over 180 days of follow-up . RESULTS Compared with stress myocardial perfusion scintigraphy ( MPS ) , CCTA was associated with an increased likelihood of subsequent cardiac catheterization ( 22.9 % vs 12.1 % ; adjusted odds ratio [ AOR ] , 2.19 [ 95 % CI , 2.08 to 2.32 ] ; P < .001 ) , percutaneous coronary intervention ( 7.8 % vs 3.4 % ; AOR , 2.49 [ 2.28 to 2.72 ] ; P < .001 ) , and coronary artery bypass graft surgery ( 3.7 % vs 1.3 % ; AOR , 3.00 [ 2.63 to 3.41 ] ; P < .001 ) . CCTA was also associated with higher total health care spending ( $ 4200 [ $ 3193 to $ 5267 ] ; P < .001 ) , which was almost entirely attributable to payments for any cl aims for CAD ( $ 4007 [ $ 3256 to $ 4835 ] ; P < .001 ) . Compared with MPS , there was lower associated spending with  stress echocardiography  ( -$4981 [ -$4991 to -$4969 ] ; P < .001 ) and  exercise electrocardiography  ( -$7449 [ -$7452 to -$7444 ] ; P < .001 ) . At 180 days , CCTA was associated with a similar likelihood of all-cause mortality ( 1.05 % vs 1.28 % ; AOR , 1.11 [ 0.88 to 1.38 ] ; P = .32 ) and a slightly lower likelihood of hospitalization for acute myocardial infa rct ion ( 0.19 % vs 0.43 % ; AOR , 0.60 [ 0.37 to 0.98 ] ; P = .04 ) . CONCLUSION Medicare beneficiaries who underwent CCTA in a nonacute setting were more likely to undergo subsequent invasive cardiac procedures and have higher CAD-related spending than patients who underwent stress testing OBJECTIVE Concerns have been raised about the radiation exposure of coronary CT angiography ( CTA ) . Recently , a prospect i ve ECG-triggered sequential coronary CTA technique was developed to reduce exposure to ionizing radiation . The purpose of this analysis was to determine the impact of a sequential scanning technique on image quality and radiation dose in a prespecified subgroup analysis of the Prospect i ve Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography I ( PROTECTION I ) Study when compared with a st and ard helical scanning technique . MATERIAL S AND METHODS This analysis comprises 685 64-MDCT coronary angiography studies of 47 international study sites in which the image quality was assessed by an experienced coronary CTA investigator using a 4-point score ( 1 = nondiagnostic , 4 = excellent image quality ) . Image quality was analyzed in all patients studied with the sequential scanning mode ( n = 99 ) and in r and omly selected patients of the population studied with the helical acquisition mode ( n = 586 ) .  Radiation dose estimates were derived from the dose-length product ( DLP ) and a conversion coefficient for the chest ( 0.014 mSv x mGy(-1 ) x cm(-1 ) ) . RESULTS Although the sequential scanning mode significantly reduced radiation dose estimates by 68 % from 11.2 mSv for the helical mode to 3.6 mSv for the sequential mode ( p < 0.001 ) , the median diagnostic image quality scores were comparable in both groups . The median diagnostic score for both scanning modes was 3.5 ( interquartile range : sequential vs helical mode , 3.25 - 3.75 vs 3.0 - 3.75 , respectively ; p = 0.62 ) . CONCLUSION The results of the PROTECTION I Study suggest that the prospect i ve ECG-triggered sequential coronary CTA technique significantly reduces radiation dose without impairing image quality when compared with the st and ard retrospective helical data acquisition in patients with a low and stable heart rate BACKGROUND Noninvasive assessment of coronary atherosclerotic plaque and significant stenosis by coronary multidetector computed tomography ( MDCT ) may improve early and accurate triage of patients presenting with acute chest pain to the emergency department . METHODS AND RESULTS We conducted a blinded , prospect i ve study in patients presenting with acute chest pain to the emergency department between May and July 2005 who were admitted to the hospital to rule out acute coronary syndrome ( ACS ) with no ischemic ECG changes and negative initial biomarkers .  Contrast-enhanced 64-slice MDCT coronary angiography was performed immediately before admission , and data sets were evaluated for the presence of coronary atherosclerotic plaque and significant coronary artery stenosis . All providers were blinded to MDCT results . An expert panel , blinded to the MDCT data , determined the presence or absence of ACS on the basis of all data accrued during the index hospitalization and 5-month follow-up . Among 103 consecutive patients ( 40 % female ; mean age , 54+/-12 years ) , 14 patients had ACS . Both the absence of significant coronary artery stenosis ( 73 of 103 patients ) and nonsignificant coronary atherosclerotic plaque ( 41 of 103 patients ) accurately predicted the absence of ACS ( negative predictive values , 100 % ) . Multivariate logistic regression analyses demonstrated that adding the extent of plaque significantly improved the initial models containing only traditional risk factors or clinical estimates of the probability of ACS ( c statistic , 0.73 to 0.89 and 0.61 to 0.86 , respectively ) . CONCLUSIONS Noninvasive assessment of coronary artery disease by MDCT has good performance characteristics for ruling out ACS in subjects presenting with possible myocardial ischemia to the emergency department and may be useful for improving early triage 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 coron 
    Output:
    
CCTA either as first line or as a layering test may represent a cost effective strategy for initial evaluation of patients with CAD prevalence of 10%-50 % in both near-term and long-term diagnostic periods .
For CAD prevalence ≥70 % , ICA as initial test may represent cost effective strategy for diagnosis of stable chest pain .
CCTA may represent cost-effective strategy when performed as a layering test to equivocal initial stress imaging before performing ICA .
Use of CCTA is cost- and time-effective strategy for evaluation of low risk ( < 30 % CAD prevalence ) acute chest pain patients in emergency department and can be used for safe exclusion of acute coronary syndrome ( ACS ) .
Use of coronary calcium score as an initial test may require further evidence to be deemed cost-effective strategy .
CCTA may represent a cost effective and may be associated with less downstream testing for diagnosis of stable chest pain patients in low to intermediate risk patients whereas for low risk acute chest pain patients , use of CCTA is associated with expedited patient management , less cost and safe exclusion of ACS