title: Subaortic right ventricular characteristics and relationship to exercise capacity in congenitally corrected transposition of the great arteries.
abstract: BACKGROUND
  In congenitally corrected transposition of the great arteries (cc-TGA), the morphologic right ventricle acts as the subaortic (systemic) ventricle, and deterioration of the ventricle over time is a well-known complication. The objective of this study was to characterize the right ventricle and explore factors that may be contributing to ventricular dilation and dysfunction and the relationship with exercise capacity.
  
  
  METHODS
  This was a prospective study of adults with cc-TGA. All patients underwent cardiopulmonary stress testing, ventricular volume and fibrosis assessment by cardiac magnetic resonance imaging, and Velocity Vector Imaging strain echocardiography.
  
  
  RESULTS
  Twenty-six patients were included (mean age, 38 ± 16 years; 54% women). Exercise capacity was significantly reduced in patients with cc-TGA compared with normal subjects (20.9 ± 6.0 vs 30.8 ± 9.2 mL/kg/min, P = .001). The majority of patients (61%) had right ventricular (RV) ejection fractions ≤ 40%. There was no evidence of fibrosis on cardiac magnetic resonance imaging. There was a significant difference in diastolic volumes among those with RV ejection fractions > 40% versus ≤ 40% (173 ± 29mL vs 233 ± 65 mL, P = .02) and moderate or severe versus no or mild tricuspid regurgitation (240 ± 80mL vs 190 ± 38mL, P = .04). RV apical longitudinal and mid free wall circumferential strain was decreased compared with these values in controls.
  
  
  CONCLUSIONS
  In this relatively "well" cc-TGA population, subaortic RV dilation, dysfunction, and exercise intolerance are a common problem. Significant systemic tricuspid atrioventricular valvular regurgitation is an important contributor to the problem. In this study, subaortic RV myocardial deformation parameters were found to be abnormal, suggesting that there is a failure of the ventricle to adapt to systemic pressures, and therapies to reduce afterload should be explored. Recurrent ischemia resulting in fibrosis likely does not contribute to RV dilation or dysfunction as demonstrated by the magnetic resonance imaging findings in this study.
authors.affiliation: Division of Cardiology, University of British Columbia Pacific Adult Congenital Heart Disease Clinic, St. Paul's Hospital, Vancouver, British Columbia, Canada. grewaljasmine@hotmail.com
authors.forename: Jasmine
authors.initials: J
authors.lastname: Grewal
authors.forename: Andrew
authors.initials: A
authors.lastname: Crean
authors.forename: Patrick
authors.initials: P
authors.lastname: Garceau
authors.forename: Rachel
authors.initials: R
authors.lastname: Wald
authors.forename: Anna
authors.initials: A
authors.lastname: Woo
authors.forename: Harry
authors.initials: H
authors.lastname: Rakowski
authors.forename: Candice K
authors.initials: CK
authors.lastname: Silversides
mesh_terms: D000328:Adult; D001011:Aorta / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D000080041:Congenitally Corrected Transposition of the Great Arteries; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D014188:Transposition of Great Vessels / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014463:Ultrasonography; D018497:Ventricular Dysfunction, Right / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*