title: 256-slice CT angiographic evaluation of coronary artery bypass grafts: effect of heart rate, heart rate variability and Z-axis location on image quality.
abstract: OBJECTIVE
  The objective of this study is to assess the effect of heart rate, heart rate variability and z-axis location on coronary artery bypass graft (CABG) image quality using a 256-slice computed tomography (CT) scanner.
  
  
  METHODS
  A total of 78 patients with 254 CABG (762 graft segments) were recruited to undergo CABG assessment with 256-slice CT and prospective ECG-gating. Two observers rated graft segments for image quality on a 5-point scale. Quantitative measurements were also made. Logistic and cumulative link mixed models were used to assess the predictors of graft image quality.
  
  
  RESULTS
  Graft image quality was judged as diagnostic (scores 5 (excellent), 4 (good) and 3 (moderate)) in 96.6% of the 762 segments. Interobserver agreement was excellent (kappa ≥0.90). Graft image quality was not affected by heart rate level. However, high heart rate variability was associated with an important and significant image quality deterioration (odds ratio 4.31; p  =  0.036). Distal graft segments had significantly lower image quality scores than proximal segments (p ≤ 0.02). Significantly higher noise was noted at the origin of the mammary grafts (p  =  0.001), owing to streak artifacts from the shoulders.
  
  
  CONCLUSIONS
  CABG imaging with 270-msec rotation 256-slice CT and prospective ECG-gating showed an adequate image quality in 96.6% of graft segments, and an excellent interobserver agreement. Graft image quality was not influenced by heart rate level. Image quality scores were however significantly decreased in patients with high heart rate variability, as well as in distal graft segments, which are closer to the heart.
authors.affiliation: Radiology, University of Montreal Medical Center (CHUM), Montreal, Quebec, Canada; Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada; Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar der Technischen Universität München, Munich, Germany.
authors.forename: Bettina M
authors.initials: BM
authors.lastname: Gramer
authors.affiliation: Radiology, University of Montreal Medical Center (CHUM), Montreal, Quebec, Canada.
authors.forename: Patricia
authors.initials: P
authors.lastname: Diez Martinez
authors.affiliation: Radiology, University of Montreal Medical Center (CHUM), Montreal, Quebec, Canada.
authors.forename: Anne S
authors.initials: AS
authors.lastname: Chin
authors.affiliation: Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada; Department of Social and Preventive Medicine, University of Montreal, Montreal, Quebec, Canada.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Sylvestre
authors.affiliation: Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada.
authors.forename: Sandra
authors.initials: S
authors.lastname: Larrivée
authors.affiliation: Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada; Cardiac Surgery, CHUM, University of Montreal and CRCHUM, Montreal, Quebec, Canada.
authors.forename: Louis-Mathieu
authors.initials: LM
authors.lastname: Stevens
authors.affiliation: Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada; Cardiac Surgery, CHUM, University of Montreal and CRCHUM, Montreal, Quebec, Canada.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Noiseux
authors.affiliation: Radiology, University of Montreal Medical Center (CHUM), Montreal, Quebec, Canada; Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada.
authors.forename: Gilles
authors.initials: G
authors.lastname: Soulez
authors.affiliation: Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar der Technischen Universität München, Munich, Germany.
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.affiliation: Radiology, University of Montreal Medical Center (CHUM), Montreal, Quebec, Canada; Research Center of the University of Montreal Medical Center (CRCHUM), Montreal, Quebec, Canada.
authors.forename: Carl
authors.initials: C
authors.lastname: Chartrand-Lefebvre
mesh_terms: D000368:Aged; D016477:Artifacts; D064592:Autografts / Q000000981:diagnostic imaging*; D017023:Coronary Angiography / Q000379:methods* / Q000592:standards; D001026:Coronary Artery Bypass / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards