title: Elevated left ventricular outflow tract velocities on exercise stress echocardiography may be a normal physiologic response in healthy youth.
abstract: BACKGROUND
  Children with heart disease are at risk for sudden death during exercise, yet decisions regarding sports participation are often based on resting data. Acceleration across the left ventricular outflow tract (LVOT) assessed on stress echocardiography may suggest a diagnosis of hypertrophic cardiomyopathy in patients in whom it is not otherwise obvious. However, the range of peak velocities across the LVOT in healthy youth is unknown. The aim of this study was to describe LVOT velocities with maximal exercise in this age group.
  
  
  METHODS
  Subjects up to 18 years old were prospectively enrolled if they had normal results on resting echocardiography and were undergoing exercise testing for other reasons. Subjects with significant comorbidities, suspected cardiomyopathy, or family histories of cardiomyopathy were excluded. Peak LVOT velocities were measured in the upright position using continuous-wave Doppler immediately after maximal exercise.
  
  
  RESULTS
  Fifty subjects (mean age, 13.8 ± 2.8 years) were included. Twenty-eight (56%) were male, and 40 (80%) were Caucasian. The median peak LVOT velocity measured immediately after exercise was 2.5 m/sec (range, 1.3-5.9 m/sec). Sixteen subjects (32%) developed peak LVOT velocities of ≥3 m/sec. Twelve of the 16 (75%) with elevated velocities had a dynamic outflow tract Doppler pattern, of whom eight had evidence of intracavitary narrowing on two-dimensional echocardiography.
  
  
  CONCLUSIONS
  The development of significant exercise-induced LVOT velocities may be a normal physiologic finding in healthy youth. The measurement of LVOT velocities alone with maximal exercise may not help distinguish patients with hypertrophic cardiomyopathy from healthy children.
authors.affiliation: Division of Cardiology, The Children's Hospital of Philadelphia and Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: wittliebc@email.chop.edu.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Wittlieb-Weber
authors.forename: Meryl S
authors.initials: MS
authors.lastname: Cohen
authors.forename: Michael G
authors.initials: MG
authors.lastname: McBride
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Paridon
authors.forename: Robert
authors.initials: R
authors.lastname: Morrow
authors.forename: Melissa
authors.initials: M
authors.lastname: Wasserman
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Paul
authors.initials: P
authors.lastname: Stephens
mesh_terms: D000293:Adolescent / Q000502:physiology*; D002312:Cardiomyopathy, Hypertrophic / Q000000981:diagnostic imaging*; D003951:Diagnostic Errors / Q000517:prevention & control*; D015150:Echocardiography, Doppler / Q000379:methods*; D005080:Exercise Test; D005189:False Positive Reactions; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014694:Ventricular Outflow Obstruction / Q000000981:diagnostic imaging*
keywords: CI; CW; Confidence interval; Continuous-wave; HCM; Hypertrophic cardiomyopathy; IQR; Interquartile range; LVOT; Left ventricular outflow tract; MR; Mitral regurgitation; Pediatric cardiology; RER; Respiratory exchange ratio; SAM; SE; Stress echocardiography; Systolic anterior motion of the mitral valve