title: A simplified D-shaped model of the mitral annulus to facilitate CT-based sizing before transcatheter mitral valve implantation.
abstract: BACKGROUND
  The nonplanar, saddle-shaped structure of the mitral annulus has been well established through decades of anatomic and echocardiographic study. Its relevance for mitral annular assessment for transcatheter mitral valve implantation is uncertain.
  
  
  OBJECTIVE
  Our objectives are to define the methodology for CT-based simplified "D-shaped" mitral annular assessment for transcatheter mitral valve implantation and compare these measurements to traditional "saddle-shaped" mitral annular assessment.
  
  
  METHODS
  The annular contour was manually segmented, and fibrous trigones were identified using electrocardiogram-gated diastolic CT data sets of 28 patients with severe functional mitral regurgitation, yielding annular perimeter, projected area, trigone-to-trigone (TT) distance, and septal-lateral distance. In contrast to the traditional saddle-shaped annulus, the D-shaped annulus was defined as being limited anteriorly by the TT distance, excluding the aortomitral continuity. Hypothetical left ventricular outflow tract (LVOT) clearance was assessed.
  
  
  RESULTS
  Projected area, perimeter, and septal-lateral distance were found to be significantly smaller for the D-shaped annulus (11.2 ± 2.7 vs 13.0 ± 3.0 cm(2); 124.1 ± 15.1 vs 136.0 ± 15.5 mm; and 32.1 ± 4.0 vs 40.1 ± 4.9 mm, respectively; P < .001). TT distances were identical (32.7 ± 4.1 mm). Hypothetical LVOT clearance was significantly lower for the saddle-shaped annulus than for the D-shaped annulus (10.7 ± 2.2 vs 17.5 ± 3.0 mm; P < .001).
  
  
  CONCLUSIONS
  By truncating the anterior horn of the saddle-shaped annular contour at the TT distance, the resulting more planar and smaller D-shaped annulus projects less onto the LVOT, yielding a significantly larger hypothetical LVOT clearance than the saddle-shaped approach. CT-based mitral annular assessment may aid preprocedural sizing, ensuring appropriate patient and device selection.
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Philipp
authors.initials: P
authors.lastname: Blanke
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Danny
authors.initials: D
authors.lastname: Dvir
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Anson
authors.initials: A
authors.lastname: Cheung
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Jian
authors.initials: J
authors.lastname: Ye
authors.affiliation: Division of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Levine
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Bruce
authors.initials: B
authors.lastname: Precious
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Adam
authors.initials: A
authors.lastname: Berger
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Dion
authors.initials: D
authors.lastname: Stub
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Cameron
authors.initials: C
authors.lastname: Hague
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Darra
authors.initials: D
authors.lastname: Murphy
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Thompson
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Brad
authors.initials: B
authors.lastname: Munt
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Moss
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Boone
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Wood
authors.affiliation: Section of Cardiovascular Radiology, Department of Radiology, University of Freiburg, Freiburg, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Pache
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Webb
authors.affiliation: Center for Heart Valve Innovation, St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada. Electronic address: jleipsic@providencehealth.bc.ca.
authors.forename: Jonathon
authors.initials: J
authors.lastname: Leipsic
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006328:Cardiac Catheterization / Q000295:instrumentation; D005260:Female; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000628:therapy*; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Computed tomography; Mitral annulus; Mitral regurgitation; Transapical mitral valve replacement; Transcatheter mitral valve implantation