title: Feasibility study of electrocardiographic and respiratory gated, gadolinium enhanced magnetic resonance angiography of pulmonary veins and the impact of heart rate and rhythm on study quality.
abstract: BACKGROUND
  We aimed to assess the feasibility of 3 dimensional (3D) respiratory and ECG gated, gadolinium enhanced magnetic resonance angiography (MRA) on a 3 Tesla (3 T) scanner for imaging pulmonary veins (PV) and left atrium (LA). The impact of heart rate (HR) and rhythm irregularity associated with atrial fibrillation (AF) on image and segmentation qualities were also assessed.
  
  
  METHODS
  101 consecutive patients underwent respiratory and ECG gated (ventricular end systolic window) MRA for pre AF ablation imaging. Image quality (assessed by PV delineation) was scored as 1 = not visualized, 2 = poor, 3 = good and 4 = excellent. Segmentation quality was scored on a similar 4 point scale. Signal to noise ratios (SNRs) were calculated for the LA, LA appendage (LAA), and PV. Contrast to noise ratios (CNRs) were calculated between myocardium and LA, LAA and PV, respectively. Associations between HR/rhythm and quality metrics were assessed.
  
  
  RESULTS
  35 of 101 (34.7%) patients were in AF at time of MRA. 100 (99%) patients had diagnostic studies, and 91 (90.1%) were of good or excellent quality. Overall, mean ± standard deviation (SD) image quality score was 3.40 ± 0.69. Inter observer agreement for image quality scores was substantial, (kappa = 0.68; 95% confidence interval (CI): 0.46, 0.90). Neither HR adjusting for rhythm [odds ratio (OR) = 1.03, 95% CI = 0.98,1.09; p = 0.22] nor rhythm adjusting for HR [OR = 1.25, 95% CI = 0.20, 7.69; p = 0.81] demonstrated association with image quality. Similarly, SNRs and CNRs were largely independent of HR after adjusting for rhythm. Segmentation quality scores were good or excellent for 77.3% of patients: mean ± SD score = 2.91 ± 0.63, and scores did not significantly differ by baseline rhythm (p = 0.78).
  
  
  CONCLUSIONS
  3D respiratory and ECG gated, gadolinium enhanced MRA of the PVs and LA on a 3 T system is feasible during ventricular end systole, achieving high image quality and high quality image segmentation when imported into electroanatomic mapping systems. Quality is independent of HR and heart rhythm for this free breathing, radiation free, alternative strategy to current MRA or CT based approaches, for pre AF ablation imaging of PVs and LA.
authors.affiliation: Cardiovascular Imaging Program, Cardiovascular Division, Department of Medicine and Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. jgroarke@partners.org.
authors.forename: John D
authors.initials: JD
authors.lastname: Groarke
authors.forename: Alfonso H
authors.initials: AH
authors.lastname: Waller
authors.forename: Tomas S
authors.initials: TS
authors.lastname: Vita
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Michaud
authors.forename: Marcelo F
authors.initials: MF
authors.lastname: Di Carli
authors.forename: Ron
authors.initials: R
authors.lastname: Blankstein
authors.forename: Raymond Y
authors.initials: RY
authors.lastname: Kwong
authors.forename: Michael
authors.initials: M
authors.lastname: Steigner
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D055424:Cardiac-Gated Imaging Techniques; D017115:Catheter Ablation; D016009:Chi-Square Distribution; D003287:Contrast Media; D004562:Electrocardiography; D005240:Feasibility Studies; D005260:Female; D006325:Heart Atria / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D006339:Heart Rate; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D016015:Logistic Models; D018810:Magnetic Resonance Angiography; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives*; D008875:Middle Aged; D017711:Nonlinear Dynamics; D015588:Observer Variation; D016017:Odds Ratio; D009942:Organometallic Compounds; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011667:Pulmonary Veins / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D015203:Reproducibility of Results; D056152:Respiratory Rate; D059629:Signal-To-Noise Ratio
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine