Cardiovascular computed tomography imaging 839

rograde approach alone and 13 (38.2%) of the attempts utilized a bidirectionalapproach. The overall success rate per attempt was 85.3%. Calcium occupying>50% of CSA by CTCA was the only predictor of failure of the antegrade ap-proach for CTO PCI; p=0.036. There were trends of longer estimated CTO dura-tion and longer estimated CTO length in the failed antegrade approaches for CTOPCI (p=0.073, p=0.063 respectively). None of the CTCA or the CCA factors wasfound to predict the outcome of the retrograde approach for CTO PCI. A trendof successful outcome of the retrograde approach for CTO PCI was noted withhigher Werner collateral channel grades (p=0.057).Conclusions: CTCA provides better means of detection and assessment of cal-cification within the coronary CTO lesions than CCA. Severe calcification (>50%of CSA by CTCA) was the only statistically significant predictor of failure of theantegrade approach for CTO PCI.

P4678 | BEDSIDEPrognostic value of coronary CT angiography and exercise ECG

A. Tralhao1, A. Miguel Ferreira2 , P. De Araujo Goncalves2, M. BorgesSantos1, H. Dores1, M. Salome Carvalho1, N. Cardim2, F. Pereira Machado2,H. Marques3. 1Hospital Santa Cruz, Carnaxide, Portugal; 2Hospital Luz,Cardiovascular Center, Lisbon, Portugal; 3Hospital Luz, Imaging Center, Lisbon,Portugal

Purpose: To assess and compare the prognostic value of coronary CT angiogra-phy (CCTA) and exercise ECG (ExECG) in patients with suspected stable anginapectoris.Methods: Patients with suspected coronary artery disease (CAD) who had un-dergone both ECG exercise stress testing (ExECG) and CCTA (within 180 days)were identified retrospectively in a single center registry. The presence of 50% orgreater coronary stenosis was assessed with CCTA. ExECG results were clas-sified as normal, ischemic, or nondiagnostic. Patients were followed-up for majoradverse cardiac events (MACE), defined as cardiac death, nonfatal myocardialinfarction, unstable angina requiring hospitalization, and revascularization >90days after index CCTA. Univariable and multivariable Cox regression analysis wasused to determine the prognostic values, and discriminative power was assessedwith continuous net reclassification improvement (cNRI).Results: Follow-up was completed for 467 patients (88%), with a median durationof 2.6 years (IQR 2.0-3.8). A total of 23 patients experienced MACE, including 3deaths and 2 non-fatal myocardial infarctions. In the univariable model, modifiedCAD Consortium 2 score (HR 1.05, 95% CI 1.02-1.08), non-obstructive CAD (HR5.63, 95% CI 1.25-25.43) and obstructive CAD (HR 15.43 CI 3.38-70.45) werepredictors of MACE. In the multivariable model, only CCTA findings remainedindependently predictive of MACE. Addition of CCTA results to the clinical andExECG model yielded a cNRI of 70% (222 reclassified upward, 245 downward).

Conclusions: CCTA findings are strongly predictive of MACE. Its prognosticpower seems superior and incremental to clinical and exercise ECG data.

P4679 | BEDSIDEThe risk of ischemic stroke is associated with coronaryatherosclerotic burden, but not with myocardial ischemia inpatients with suspected coronary artery disease

H.S. Lee1, Y.J. Kim1, Y.E. Yoon2, H.L. Kim3, S.P. Lee1, H.K. Kim1, G.Y. Cho2,D.W. Sohn1, B.H. Oh1, Y.B. Park1. 1Seoul National University Hospital,Department of Internal Medicine, Division of Cardiology, Seoul, Korea, Republicof; 2Seoul National University Bun-Dang Hospital, Department of Internalmedicine, Division of Cardiology, Seoul, Korea, Republic of; 3Seoul NationalUniversity Boramae Hospital, Seoul, Korea, Republic of

Purpose: We sought to evaluate whether coronary artery disease (CAD) evalu-ated by coronary computed tomographic angiography (CCTA) and photon emis-sion computed tomography (SPECT) are related to the risk of future ischemicstroke in patients with suspected CAD.Methods: From 1874 consecutive patients undergoing both 64-slice CCTA andSPECT for the evaluation of CAD between 2004 and 2011, 516 patients with his-tory of CAD, 148 patients with history of ischemic stroke, and 56 patients with lackof clinical information were excluded. Among them (n=1154), follow-up informa-tion was obtained for the occurrence of ischemic stroke in 1137 subjects (98.5%).

Kaplan-Meier survival model and cox proportional hazards model were used forthe analysis.Results: During a median follow-up of 26 months (interquartile range 14 to 43months), ischemic stroke occurred in 25 of 1137 patients (2.2%). The presenceof CAD on CCTA was associated with a >4-fold hazard increase for ischemicstroke (unadjusted HR 4.38, 95% CI 1.03-18.64, p = 0.029). Furthermore, CADinvolving two or more vessels on CCTA demonstrated a >3-fold hazard increasefor ischemic stroke compared to 1-vessel involvement (unadjusted HR 3.68, 95%CI 1.57-8.62, p = 0.003). In contrast, the presence of perfusion defect (PD) onSPECT was not associated with ischemic stroke (unadjusted HR 0.87, 95% CI0.36-2.09, p = 0.747). PD with summed stress score (SSS) ≥8 did not show thehazard increase for ischemic stroke compared to that with SSS <8 (unadjustedHR 0.49, 95% CI 0.07-3.69, p = 0.493).

Kaplan-Meier event-free survival by CCTA

Conclusions: The risk of ischemic stroke is associated with coronary atheroscle-rotic burden but not with myocardial ischemic burden. It seems that CCTA canprovide additional information with regard to the risk of future ischemic stroke inpatients with suspected CAD.

P4680 | BEDSIDEProspective randomized trial on radiation dose estimates of CTangiography in patients applying Iterative image reconstructiontechniques - results of the PROTECTION V study

S.D.C. Deseive1, A.L. Menges1, J. Leipsic2, G. Korosoglou3, S. Mirsadraee4,E. Martuscelli5, M. Chen6, S. Martinoff7, M. Hadamitzky7, J. Hausleiter8.1German Heart Center, Clinic for Heart and Circulatory Diseases, Munich,Germany; 2St. Paul’s Hospital, Vancouver, Canada; 3University Hospital ofHeidelberg, Department of Cardiology, Heidelberg, Germany; 4University ofEdinburgh, Clinical Research Imaging Centre, Edinburgh, United Kingdom;5University of Rome, Polyclinic "Tor Vergata", Department of Internal Medicine,Rome, Italy; 6National Institutes of Health, Clinical Center, Radiology andImaging Sciences, Bethesda, United States of America; 7German Heart Center,Department of Radiology and Nuclear Medicine, TUM, Munich, Germany;8Ludwig-Maximilians University, Department of Cardiology, Munich, Germany

Introduction: Despite a significant reduction of radiation dose associated withcoronary CT angiography (CCTA) over the last decade, concerns still exist aboutthe radiation exposure and the very low stochastic risk for the developmentof radiation-induced cancer. Recently, iterative image reconstruction algorithmshave been developed by different CT vendors, possibly allowing for reduced tubecurrent leading to lower radiation dose.Objectives: The PROTECTION V study investigates the impact of reduced tubecurrent combined with iterative image reconstruction techniques in comparisonto standard cCTA (using standard tube current levels with traditional filtered backprojection image reconstruction) on diagnostic image quality and radiation dose.Methods: The PROTECTION V study is an international, prospective, random-ized, multi-center, multi-vendor clinical trial. 400 patients were randomized to ei-ther one of the groups described above. All participating centres were highlyencouraged to use axial image acquisition and other available dose reductionstrategies. The primary study end point was to prove non-inferior diagnostic im-age quality with iterative image reconstruction and reduced tube current in com-parison to standard image acquisition (predifined margin of inferiority 0.2). Imagequality was assessed using a nominal scale ranging from 1 to 4 - 1 representingnon-diagnostic image quality, 4 representing excellent image quality). Secondarystudy endpoints were radiation dose and the need for downstream testing within30 days after coronary cCTA.Results: Patient recruitment is complete and data is currently being analysed.Radiation dose is currently available for 166 patients in the conventional group(3.2 mSv) and 171 patients in the group using reduced tube voltage and iterativeimage reconstruction (2.3 mSv), corresponding to a dose reduction of 28.1%. Fullresults including image quality, radiation dose and 30 day follow-up for all patientswill be presented.

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