***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: OBJECTIVES The aim of this study was to determine the diagnostic performance of a new method for quantifying fractional flow reserve ( FFR ) with computational fluid dynamics ( CFD ) applied to coronary computed tomography angiography ( CCTA ) data in patients with suspected or known coronary artery disease ( CAD ) . BACKGROUND Measurement of FFR during invasive coronary angiography is the gold st and ard for identifying coronary artery lesions that cause ischemia and improves clinical decision-making for revascularization . Computation of FFR from CCTA data ( FFR(CT ) ) provides a noninvasive method for identifying ischemia-causing stenosis ; however , the diagnostic performance of this new method is unknown . METHODS Computation of FFR from CCTA data was performed on 159 vessels in 103 patients undergoing CCTA , invasive coronary angiography , and FFR .  Independent core laboratories determined FFR(CT ) and CAD stenosis severity by CCTA . Ischemia was defined by an FFR(CT ) and FFR ≤0.80 , and anatomically obstructive CAD was defined as a CCTA with stenosis ≥50 % . Diagnostic performance of FFR(CT ) and CCTA stenosis was assessed with invasive FFR as the reference st and ard . RESULTS Fifty-six percent of patients had ≥1 vessel with FFR ≤0.80 . On a per-vessel basis , the accuracy , sensitivity , specificity , positive predictive value , and negative predictive value were 84.3 % , 87.9 % , 82.2 % , 73.9 % , 92.2 % , respectively , for FFR(CT ) and were 58.5 % , 91.4 % , 39.6 % , 46.5 % , 88.9 % , respectively , for CCTA stenosis . The area under the receiver-operator characteristics curve was 0.90 for FFR(CT ) and 0.75 for CCTA ( p = 0.001 ) . The FFR(CT ) and FFR were well correlated ( r = 0.717 , p < 0.001 ) with a slight underestimation by FFR(CT ) ( 0.022 ± 0.116 , p = 0.016 ) . CONCLUSIONS Noninvasive FFR derived from CCTA is a novel method with high diagnostic performance for the detection and exclusion of coronary lesions that cause ischemia STUDY OBJECTIVE Coronary computed tomographic ( CT ) angiography has excellent performance characteristics relative to coronary angiography and exercise or pharmacologic stress testing . We hypothesize that coronary CT angiography can identify a cohort of emergency department ( ED ) patients with a potential acute coronary syndrome who can be safely discharged with a less than 1 % risk of 30-day cardiovascular death or nonfatal myocardial infa rct ion . METHODS We conducted a prospect i ve cohort study at an urban university hospital ED that enrolled consecutive patients with potential acute coronary syndromes and a low TIMI risk score who presented to the ED with symptoms suggestive of a potential acute coronary syndrome and received a coronary CT angiography .  Our intervention was either immediate coronary CT angiography in the ED or after a 9- to 12-hour observation period that included cardiac marker determinations , depending on time of day . The main clinical outcome was 30-day cardiovascular death or nonfatal myocardial infa rct ion . RESULTS Five hundred sixty-eight patients with potential acute coronary syndrome were evaluated : 285 of these received coronary CT angiography immediately in the ED and 283 received coronary CT angiography after a brief observation period . Four hundred seventy-six ( 84 % ) were discharged home after coronary CT angiography . During the 30-day follow-up period , no patients died of a cardiovascular event ( 0 % ; 95 % confidence interval [ CI ] 0 % to 0.8 % ) or sustained a nonfatal myocardial infa rct ion ( 0 % ; 95 % CI 0 to 0.8 % ) . CONCLUSION ED patients with symptoms concerning for a potential acute coronary syndrome with a low TIMI risk score and a nonischemic initial ECG result can be safely discharged home after a negative coronary CT angiography test result 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 With the advent of multislice CT more than a decade ago , multislice CT angiography has demonstrated a huge potential in the less invasive imaging of cardiovascular disease , especially in the diagnosis of coronary artery disease . The diagnostic accuracy of multislice CT angiography has been significantly augmented with the rapid technical developments ranging from the initial 4-slice , to the current 64-slice and 256 and 320-slice CT scanners . This is mainly demonstrated by the improved spatial and temporal resolution when compared to the earlier type of CT scanners . Traditionally , multislice CT angiography is acquired with retrospective ECG-gating with acquisition of volume data at the expense of increased radiation dose , since data is acquired at the entire cardiac cycle , although not all of them are used for postprocessing or reconstructions . Recently , there is an increasing trend of utilising prospect i ve ECG-gating in cardiac imaging with latest multislice CT scanners ( 64 or more slices ) with significant reduction of radiation dose when compared to retrospective ECG-gating method . However , there is some debate as to the diagnostic value of prospect i ve ECG-gating in the diagnosis of coronary artery disease , despite its attractive ability to reduce radiation dose . This article will review the performance of retrospective ECG-gating in the diagnostic value of coronary artery disease , highlight the potential applications of prospect i ve ECG-gating , and explore the future directions of multislice CT angiography in cardiac imaging OBJECTIVES The goal of this study was to determine the diagnostic performance of noninvasive fractional flow reserve ( FFR ) derived from st and ard acquired coronary computed tomography angiography ( CTA ) data sets ( FFR(CT ) ) for the diagnosis of myocardial ischemia in patients with suspected stable coronary artery disease ( CAD ) . BACKGROUND FFR measured during invasive coronary angiography ( ICA ) is the gold st and ard for lesion-specific coronary revascularization decisions in patients with stable CAD . The potential for FFR(CT ) to noninvasively identify ischemia in patients with suspected CAD has not been sufficiently investigated . METHODS This prospect i ve multicenter trial included 254 patients scheduled to undergo clinical ly indicated ICA for suspected CAD .  Coronary CTA was performed before ICA . Evaluation of stenosis ( > 50 % lumen reduction ) in coronary CTA was performed by local investigators and in ICA by an independent core laboratory . FFR(CT ) was calculated and interpreted in a blinded fashion by an independent core laboratory . Results were compared with invasively measured FFR , with ischemia defined as FFR(CT ) or FFR ≤0.80 . RESULTS The area under the receiver-operating characteristic curve for FFR(CT ) was 0.90 ( 95 % confidence interval [ CI ] : 0.87 to 0.94 ) versus 0.81 ( 95 % CI : 0.76 to 0.87 ) for coronary CTA ( p = 0.0008 ) . Per-patient sensitivity and specificity ( 95 % CI ) to identify myocardial ischemia were 86 % ( 95 % CI : 77 % to 92 % ) and 79 % ( 95 % CI : 72 % to 84 % ) for FFR(CT ) versus 94 % ( 86 to 97 ) and 34 % ( 95 % CI : 27 % to 41 % ) for coronary CTA , and 64 % ( 95 % CI : 53 % to 74 % ) and 83 % ( 95 % CI : 77 % to 88 % ) for ICA , respectively . In patients ( n = 235 ) with intermediate stenosis ( 95 % CI : 30 % to 70 % ) , the diagnostic accuracy of FFR(CT ) remained high . CONCLUSIONS FFR(CT ) provides high diagnostic accuracy and discrimination for the diagnosis of hemodynamically significant CAD with invasive FFR as the reference st and ard . When compared with anatomic testing by using coronary CTA , FFR(CT ) led to a marked increase in specificity . ( HeartFlowNXT-HeartFlow Analysis of Coronary Blood Flow Using Coronary CT Angiography [ HFNXT ] ; NCT01757678 ) OBJECTIVES We prospect ively studied the prognostic value of predischarge dobutamine stress echocardiography ( DSE ) in low-risk chest pain patients with a normal or nondiagnostic electrocardiogram ( ECG ) and a negative serial troponin T. BACKGROUND Noninvasive stress testing is recommended before discharge or within 72 h in patients with low-risk chest pain . The prognostic value of immediate DSE has not been studied in a blinded , prospect i ve fashion . METHODS Patients presenting at the emergency room within 6 h of symptom onset and a normal or nondiagnostic ECG were eligible .  Dobutamine stress echocardiography was performed after unstable coronary artery disease was ruled out by a st and ard rule-out protocol and a negative serial troponin T ; the occurrence of any new wall motion abnormality was considered positive . Results were kept blinded . End points were cardiac death , myocardial infa rct ion , rehospitalization for unstable angina or revascularization . RESULTS In total , 377 patients were included . There were 2 deaths , 2 myocardial infa rct ions , 8 rehospitalization for unstable angina , and 10 revascularizations at six-month follow-up . The end points occurred in 8/26 ( 30.8 % ) patients with a positive versus 14/351 ( 4.0 % ) patients with a negative DSE ( odds ratio , 10.7 ; 95 % confidence interval , 4.0 to 28.8 ; p < 0.0001 ) . By multivariate analysis , DSE remained a predictor of end points ( p < 0.0001 ) . CONCLUSIONS A predischarge DSE had important , independent prognostic value in low-risk , troponin negative , chest pain patients Objectives To assess feasibility , image quality , and radiation dose of prospect ively ECG-triggered coronary CT angiography ( CTA ) in orthotopic heart transplant ( OHT ) recipients . Methods 47 consecutive OHT recipients ( 40 men , mean age 62.1±10.9 years , mean heart rate 86.3±14.4 bpm ) underwent  dual- source CTA to rule out coronary allograft vasculopathy in a prospect ively ECG-triggered mode with data acquisition during 35 % to 45 % of the cardiac cycle . Two independent observers blindly assessed image quality on a per-segment and per-vessel basis using a four-point scale ( 1- 
    Output:
    
Bivariate analysis revealed that CCTA had statistically greater sensitivity , specificity , PPV and overall diagnostic accuracy when compared to SE and SPECT .
CONCLUSIONS All three modalities , when employed by an experienced clinician , are highly accurate .
Each has its own strengths and limitations making each well suited for different patient groups .
CCTA has higher accuracy than SE and SPECT , but it has many drawbacks , most importantly its lack of physiologic data