title: Mitral valve abnormalities identified by cardiovascular magnetic resonance represent a primary phenotypic expression of hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Whether morphological abnormalities of the mitral valve represent part of the hypertrophic cardiomyopathy (HCM) disease process is unresolved. Therefore, we applied cardiovascular magnetic resonance to characterize mitral valve morphology in a large HCM cohort.
  
  
  RESULTS
  Cine cardiac magnetic resonance images were obtained in 172 HCM patients (age, 42±18 years; 62% men) and 172 control subjects. In addition, 15 HCM gene-positive/phenotype-negative relatives were studied. Anterior mitral leaflet (AML) and posterior mitral leaflet lengths were greater in HCM patients than in control subjects (26±5 versus 19±5 mm, P<0.001; and 14±4 versus 10±3 mm, P<0.001, respectively), including 59 patients (34%) in whom AML length alone, posterior mitral leaflet length alone, or both were particularly substantial (>2 SDs above controls). Leaflet length was increased compared with controls in virtually all HCM age groups, including young patients 15 to 20 years of age (AML, 26±5 versus 21±4 mm; P=0.0002) and those ≥60 years of age (AML, 26±4 versus 19±2 mm; P<0.001). No relation was evident between mitral leaflet length and LV thickness or mass index (P=0.09 and P=0.16, respectively). A ratio of AML length to LV outflow tract diameter of >2.0 was associated with subaortic obstruction (P=0.001). In addition, AML length in 15 genotype-positive relatives without LV hypertrophy exceeded that of matched control subjects (21±3 versus 18±3 mm; P<0.01).
  
  
  CONCLUSIONS
  In HCM, mitral valve leaflets are elongated independently of other disease variables, likely constituting a primary phenotypic expression of this heterogeneous disease, and are an important morphological abnormality responsible for LV outflow obstruction in combination with small outflow tract dimension. These findings suggest a novel role for cardiac magnetic resonance in the assessment of HCM.
authors.affiliation: Hypertrophic Cardiomyopathy Center, Division of Cardiology, Tufts Medical Center, No. 70, 800 Washington St, Boston, MA 02111, USA. mmaron@tuftsmedialcenter.org
authors.forename: Martin S
authors.initials: MS
authors.lastname: Maron
authors.forename: Iacopo
authors.initials: I
authors.lastname: Olivotto
authors.forename: Caitlin
authors.initials: C
authors.lastname: Harrigan
authors.forename: Evan
authors.initials: E
authors.lastname: Appelbaum
authors.forename: C Michael
authors.initials: CM
authors.lastname: Gibson
authors.forename: John R
authors.initials: JR
authors.lastname: Lesser
authors.forename: Tammy S
authors.initials: TS
authors.lastname: Haas
authors.forename: James E
authors.initials: JE
authors.lastname: Udelson
authors.forename: Warren J
authors.initials: WJ
authors.lastname: Manning
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Maron
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002312:Cardiomyopathy, Hypertrophic / Q000473:pathology* / Q000503:physiopathology; D016022:Case-Control Studies; D002648:Child; D015331:Cohort Studies; D005260:Female; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000473:pathology / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000473:pathology* / Q000503:physiopathology; D010641:Phenotype; D014694:Ventricular Outflow Obstruction / Q000473:pathology / Q000503:physiopathology; D055815:Young Adult