title: Left ventricular function quantified by myocardial strain imaging in small-breed dogs with chronic mitral regurgitation.
abstract: BACKGROUND
  The presence of left ventricular (LV) systolic dysfunction may influence prognosis or therapy in dogs with chronic mitral regurgitation (MR). Assessment of LV function in MR by conventional echocardiography is confounded by altered ventricular loading. Myocardial deformation (strain) imaging might offer more sensitive estimates of LV function in this disease.
  
  
  OBJECTIVE
  Prospectively measure myocardial strain in dogs with asymptomatic MR compared to a control group.
  
  
  METHODS
  Forty healthy dogs (3.5-11.5 kg): 20 Controls; 20 dogs with MR and LV remodeling (Stage B2), were evaluated in this study. LV size and function were assessed in a short-axis plane. Segmental radial strain and strain rate and global circumferential strain were measured using a 2D echocardiographic speckle-tracking algorithm (GE EchoPAC). Groups were compared using Bonferroni t-tests. Influences of heart rate and body weight were explored with linear regression.
  
  
  RESULTS
  The MR group had significantly greater mean values for heart rate, LV size, and LV systolic function. Specifically, LV diastolic diameter, diastole area, shortening fraction, averaged peak systolic and early diastolic radial strain, global circumferential strain, and averaged radial strain rate were significantly greater in the MR group (p < 0.015 to p < 0.001). Strain was unrelated to weight, but weakly correlated with heart rate.
  
  
  CONCLUSIONS
  Similar to conventional indices, Stage B2 dogs with MR demonstrate hyperdynamic deformation in the short-axis plane. Short-axis strain variables measured by 2D speckle tracking are greater than for controls of similar age and weight. These results imply either preserved LV systolic function or that LV dysfunction is masked by altered ventricular loading.
authors.affiliation: Department of Veterinary Clinical Sciences and Veterinary Medical Center, The Ohio State University College of Veterinary Medicine, 601 Vernon L Tharp St., Columbus, OH 43210, USA.
authors.forename: Danielle N
authors.initials: DN
authors.lastname: Smith
authors.forename: John D
authors.initials: JD
authors.lastname: Bonagura
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Culwell
authors.forename: Karsten E
authors.initials: KE
authors.lastname: Schober
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D049628:Body Size; D002908:Chronic Disease; D004285:Dogs; D006352:Heart Ventricles; D008944:Mitral Valve Insufficiency / Q000662:veterinary*; D016276:Ventricular Function / Q000502:physiology*