title: Tissue Doppler imaging during exercise stress echocardiography demonstrates a mechanism for impaired exercise performance in children with hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Hypertrophic cardiomyopathy (HCM) is associated with decreased exercise tolerance in children, presumably due to diastolic dysfunction. Modern imaging techniques to assess myocardial function during active exercise have not been applied to this population. We hypothesized that impaired contractile reserve, as assessed by tissue Doppler imaging (TDI) and strain, contributes to reduced exercise capacity in affected individuals.
  
  
  METHODS
  Children (<18 years) with HCM and healthy age- and sex-matched controls were prospectively enrolled. Resting echocardiograms and staged upright cycle ergometry with simultaneous echocardiograms were performed. During exercise, left ventricular outflow tract (LVOT) gradients and color Doppler maps of apical four-chamber and parasternal short-axis views were obtained. Post processing of images was performed to obtain TDI velocities, and measurements of strain were attempted. Exercise parameters and staged TDI values were compared.
  
  
  RESULTS
  The study population consisted of 58 subjects (22 with HCM and 36 controls). Patients with HCM had significantly higher peak LVOT gradients compared to controls at baseline and at each exercise stage. TDI revealed that diastolic function, as assessed by E' velocities at septal and lateral mitral annuli, normalized with exercise in HCM patients. Further, systolic function (S' velocity) of HCM patients at rest was normal but failed to augment normally at peak exercise.
  
  
  CONCLUSIONS
  Children with HCM have decreased TDI velocities at rest. With exercise, they may increase their E' velocities but fail to augment S' velocities, demonstrating decreased contractile reserve. In the patient with suspected HCM but equivocal findings, exercise TDI assessment may complement the diagnostic evaluation.
authors.affiliation: Sibley Heart Center/Children's Healthcare of Atlanta, Emory University, Atlanta, Georgia.
authors.forename: Matthew Eric
authors.initials: ME
authors.lastname: Ferguson
authors.affiliation: Sibley Heart Center/Children's Healthcare of Atlanta, Emory University, Atlanta, Georgia.
authors.forename: Ritu
authors.initials: R
authors.lastname: Sachdeva
authors.affiliation: Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Gillespie
authors.affiliation: Children's Healthcare of Atlanta, Atlanta, Georgia.
authors.forename: Gemma
authors.initials: G
authors.lastname: Morrow
authors.affiliation: Sibley Heart Center/Children's Healthcare of Atlanta, Emory University, Atlanta, Georgia.
authors.forename: William
authors.initials: W
authors.lastname: Border
mesh_terms: D000293:Adolescent; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D002648:Child; D003971:Diastole; D015150:Echocardiography, Doppler / Q000379:methods; D025401:Echocardiography, Stress / Q000379:methods*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D011446:Prospective Studies; D012146:Rest / Q000502:physiology; D013599:Systole; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology
keywords: exercise stress echocardiography; hypertrophic cardiomyopathy; tissue Doppler imaging