title: Prevalence of exercise-induced left ventricular outflow tract obstruction in symptomatic patients with non-obstructive hypertrophic cardiomyopathy.
abstract: BACKGROUND
  Resting left ventricular outflow tract obstruction (LVOTO) occurs in 25% of patients with hypertrophic cardiomyopathy (HCM) and is an important cause of symptoms and disease progression. The prevalence and clinical significance of exercise induced LVOTO in patients with symptomatic non-obstructive HCM is uncertain.
  
  
  RESULTS
  87 symptomatic patients (43.3 (13.7) years, 67.8% males) with HCM and no previously documented LVOTO (defined as a gradient >or=30 mm Hg) underwent echocardiography during upright cardiopulmonary exercise testing: 54 patients (62.1%; 95% CI 51.5 to 71.6) developed LVOTO during exercise (latent LVOTO); 33 (37.9%; 95% CI 28.4 to 48.5) had neither resting nor exercise LVOTO (non-obstructive). Patients with latent LVOTO were more likely to have systolic anterior motion of the mitral valve (SAM) at rest (relative risk 2.1, 95% CI 1.2 to 3.8; p = 0.01), and higher peak oxygen consumption (mean difference: 10.3%, 95% CI 2.1 to 18.5; p = 0.02) than patients with non-obstructive HCM. The only independent predictors of Delta gradient during exercise were a history of presyncope/syncope, incomplete/complete SAM at rest and Wigle score (all p<0.05). Subsequent invasive reduction of LVOTO in 10 patients with latent obstruction and drug refractory symptoms resulted in improved functional class and less syncope/presyncope (all p<0.05).
  
  
  CONCLUSIONS
  Approximately two-thirds of patients with symptomatic non-obstructive HCM have latent LVOTO. This study suggests that all patients with symptomatic non-obstructive HCM should have exercise stress echocardiography.
authors.affiliation: The Heart Hospital, University College London, UK.
authors.forename: J S
authors.initials: JS
authors.lastname: Shah
authors.forename: M T T
authors.initials: MT
authors.lastname: Esteban
authors.forename: R
authors.initials: R
authors.lastname: Thaman
authors.forename: R
authors.initials: R
authors.lastname: Sharma
authors.forename: B
authors.initials: B
authors.lastname: Mist
authors.forename: A
authors.initials: A
authors.lastname: Pantazis
authors.forename: D
authors.initials: D
authors.lastname: Ward
authors.forename: S K
authors.initials: SK
authors.lastname: Kohli
authors.forename: S P
authors.initials: SP
authors.lastname: Page
authors.forename: C
authors.initials: C
authors.lastname: Demetrescu
authors.forename: E
authors.initials: E
authors.lastname: Sevdalis
authors.forename: A
authors.initials: A
authors.lastname: Keren
authors.forename: D
authors.initials: D
authors.lastname: Pellerin
authors.forename: W J
authors.initials: WJ
authors.lastname: McKenna
authors.forename: P M
authors.initials: PM
authors.lastname: Elliott
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002312:Cardiomyopathy, Hypertrophic / Q000209:etiology* / Q000503:physiopathology; D004452:Echocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D014694:Ventricular Outflow Obstruction / Q000209:etiology* / Q000503:physiopathology