title: A simplified and reproducible method to size the mitral annulus: implications for transcatheter mitral valve replacement.
abstract: OBJECTIVE
  Transcatheter mitral valve replacement (TMVR) provides definitive valve replacement through a minimally invasive procedure. In the setting of TMVR, it remains unclear how relevant the differences between different mitral annular (MA) diameters are. We sought to define a simplified and reproducible method to describe the MA size.
  
  
  RESULTS
  Using cardiac computed tomography angiography (CTA) studies of 47 patients, 3D MA perimeter (P3D) was annotated. The aorto-mitral continuity was excluded from MA contour either by manual annotation (yielding a saddle-shape model) or by simple truncation at the medial and lateral trigones (yielding a D-shape model). The method of the least squares was used to generate the projected MA area (Aproj) and perimeter (Pproj). Intercommissural (IC) and septolateral (SL) diameters, Dmean = (IC diameter + SL diameter)/2, area-derived diameter (DArea = 2 x √(A/π)) and perimeter-derived diameter (DPerimeter = P/π) were measured. MA eccentricity, height, and calcification (MAC) were assessed. Thirty studies were re-read by the same and by another observer to test intra- and inter-observer reproducibility. Patients (age, 75 ± 12 years, 66% males) had a wide range of mitral regurgitation severity (none-trace in 8%, mild in 55%, moderate-severe in 37%), MA size (area: 5-16 cm2), eccentricity (-8-52%), and height (3-11 mm). MAC was seen in 11 cases, in whom MAC arc occupied 26 ± 20% of the MA circumference. DArea (36.0 ± 4.0 mm) and DPerimeter (37.1 ± 3.8 mm) correlated strongly (R2 = 0.97) and were not significantly different (P = 0.15). The IC (39.3 ± 4.6 mm) and the SL (31.4 ± 4.5 mm) diameters were significantly different from DArea (P < 0.001) while Dmean (35.4 ± 4.0 mm) was not (P = 0.5). The correlation of DArea was stronger with Dmean (R2 = 0.96) than with IC and SL diameters (R2 = 0.69 and 0.76, respectively). The average difference between DArea and Dmean was +0.6 mm and the 95% limits of agreement were 2.1 and -0.9 mm. Similar results were found when the D-shape model was applied. All MA diameters showed good reproducibility with high intraclass correlation coefficient (0.93-0.98), small average bias (0.37-1.1 mm), and low coefficient of variation (3-7%) for intra- and inter-observer comparisons. Reproducibility of DArea was lower in patients with MAC.
  
  
  CONCLUSIONS
  MA sizing by CTA is readily feasible and reproducible. Dmean is a simple index that can be used to infer the effective MA size.
authors.affiliation: Depatment of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Abdelghani
authors.affiliation: Cardialysis Clinical Trials Management and Core Laboratories, Rotterdam, The Netherlands.|Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Ernest
authors.initials: E
authors.lastname: Spitzer
authors.affiliation: Cardialysis Clinical Trials Management and Core Laboratories, Rotterdam, The Netherlands.|Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Osama I I
authors.initials: OII
authors.lastname: Soliman
authors.affiliation: Department of Biomedical Imaging and Image Guided Therapy, Medical University Vienna, Vienna, Austria.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Beitzke
authors.affiliation: Department of Biomedical Imaging and Image Guided Therapy, Medical University Vienna, Vienna, Austria.
authors.forename: Roberta
authors.initials: R
authors.lastname: Laggner
authors.affiliation: Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Rafael
authors.initials: R
authors.lastname: Cavalcante
authors.affiliation: Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Tateishi
authors.affiliation: The Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.|Hospital Israelita Albert Einstein, São Paulo, Brazil.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Campos
authors.affiliation: 3mensio Medical Imaging BV, Bilthoven, The Netherlands.
authors.forename: Luc
authors.initials: L
authors.lastname: Verstraeten
authors.affiliation: Depatment of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Sotomi
authors.affiliation: Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Erhan
authors.initials: E
authors.lastname: Tenekecioglu
authors.affiliation: Cardialysis Clinical Trials Management and Core Laboratories, Rotterdam, The Netherlands.|Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Onuma
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Tijssen
authors.affiliation: Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: de Winter
authors.affiliation: Department of Cardiothoracic Surgery, University Hospital of Zurich, Zurich, Switzerland.
authors.forename: Francesco
authors.initials: F
authors.lastname: Maisano
authors.affiliation: Cardiovascular Science Division of the NHLI within Imperial, College of Science, Technology and Medicine, London, UK.
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Serruys
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006328:Cardiac Catheterization / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006350:Heart Valve Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D008943:Mitral Valve / Q000000981:diagnostic imaging*; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging* / Q000601:surgery*; D011446:Prospective Studies; D019919:Prosthesis Implantation / Q000379:methods*; D015203:Reproducibility of Results; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
keywords: Computed tomography; Mitral annulus; Mitral regurgitation; Mitral valve; Transcatheter mitral valve replacement