title: Contribution of mitral valve leaflet length and septal wall thickness to outflow tract obstruction in patients with hypertrophic cardiomyopathy.
abstract: We sought to examine whether elongation of the mitral valve leaflets in patients with hypertrophic cardiomyopathy (HCM) is synergistic to septal wall thickness (SWT) in the development of left ventricular outflow tract obstruction (LVOTO). HCM is a common genetic cardiac disease characterized by asymmetric septal hypertrophy and predisposition towards LVOTO. It has been reported that elongation of the mitral valve leaflets may be a primary phenotypic feature and contribute to LVOTO. However, the relative contribution of this finding versus SWT has not been studied. 152 patients (76 with HCM and 76 non-diseased age, race and BSA-matched controls) and 18 young, healthy volunteers were studied. SWT and the anterior mitral valve leaflet length (AMVLL) were measured using cine MRI. The combined contribution of these variables (SWT × AMVLL) was described as the Septal Anterior Leaflet Product (SALP). Peak LVOT pressure gradient was determined by Doppler interrogation and defined as "obstructive" if ≥ 30 mmHg. Patients with HCM were confirmed to have increased AMVLL compared with controls and volunteers (p < 0.01). Among HCM patients, both SWT and SALP were significantly higher in patients with LVOTO (N = 17) versus without. SALP showed modest improvement in predictive accuracy for LVOTO (AUC = 0.81) among the HCM population versus SWT alone (AUC = 0.77). However, in isolated patients this variable identified patients with LVOTO despite modest SWT. Elongation of the AMVLL is a primary phenotypic feature of HCM. While incremental contributions to LVOTO appear modest at a population level, specific patients may have dominant contribution to LVOTO. The combined marker of SALP allows for maintained identification of such patients despite modest increases in SWT.
authors.affiliation: Department of Medicine, London Health Sciences Centre, London, ON, Canada.
authors.forename: Kareem
authors.initials: K
authors.lastname: Morant
authors.affiliation: Stephenson Cardiac Imaging Centre at Libin Cardiovascular Institute of Alberta, University of Calgary, Suite 0700 - Special Services Building, Foothills Medical Centre, 1403 - 29th Street NW, Calgary, AB, T2N 2T9, Canada.|Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mikami
authors.affiliation: Imaging Research Laboratory- Robarts Research Institute, Western University, London, ON, Canada.
authors.forename: Immaculate
authors.initials: I
authors.lastname: Nevis
authors.affiliation: Department of Medicine, London Health Sciences Centre, London, ON, Canada.
authors.forename: David
authors.initials: D
authors.lastname: McCarty
authors.affiliation: Imaging Research Laboratory- Robarts Research Institute, Western University, London, ON, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Stirrat
authors.affiliation: Imaging Research Laboratory- Robarts Research Institute, Western University, London, ON, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Scholl
authors.affiliation: Imaging Research Laboratory- Robarts Research Institute, Western University, London, ON, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Rajchl
authors.affiliation: Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Giannoccaro
authors.affiliation: Stephenson Cardiac Imaging Centre at Libin Cardiovascular Institute of Alberta, University of Calgary, Suite 0700 - Special Services Building, Foothills Medical Centre, 1403 - 29th Street NW, Calgary, AB, T2N 2T9, Canada.|Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Louis
authors.initials: L
authors.lastname: Kolman
authors.affiliation: Stephenson Cardiac Imaging Centre at Libin Cardiovascular Institute of Alberta, University of Calgary, Suite 0700 - Special Services Building, Foothills Medical Centre, 1403 - 29th Street NW, Calgary, AB, T2N 2T9, Canada.|Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Bobby
authors.initials: B
authors.lastname: Heydari
authors.affiliation: Stephenson Cardiac Imaging Centre at Libin Cardiovascular Institute of Alberta, University of Calgary, Suite 0700 - Special Services Building, Foothills Medical Centre, 1403 - 29th Street NW, Calgary, AB, T2N 2T9, Canada.|Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Carmen
authors.initials: C
authors.lastname: Lydell
authors.affiliation: Stephenson Cardiac Imaging Centre at Libin Cardiovascular Institute of Alberta, University of Calgary, Suite 0700 - Special Services Building, Foothills Medical Centre, 1403 - 29th Street NW, Calgary, AB, T2N 2T9, Canada.|Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Howarth
authors.affiliation: Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Grant
authors.affiliation: Department of Medicine, London Health Sciences Centre, London, ON, Canada. jawhit@ucalgary.ca.|Stephenson Cardiac Imaging Centre at Libin Cardiovascular Institute of Alberta, University of Calgary, Suite 0700 - Special Services Building, Foothills Medical Centre, 1403 - 29th Street NW, Calgary, AB, T2N 2T9, Canada. jawhit@ucalgary.ca.|Department of Cardiac Sciences at Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada. jawhit@ucalgary.ca.
authors.forename: James A
authors.initials: JA
authors.lastname: White
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016022:Case-Control Studies; D015150:Echocardiography, Doppler; D005260:Female; D006346:Heart Septum / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015588:Observer Variation; D011237:Predictive Value of Tests; D012372:ROC Curve; D012042:Registries; D015203:Reproducibility of Results; D016277:Ventricular Function, Left; D014694:Ventricular Outflow Obstruction / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology
keywords: Cardiac magnetic resonance; Hypertrophic cardiomyopathy; LVOTO; Mitral valve leaflet length; Septal thickness