title: Clinical characteristics and outcomes of patients with hypertrophic cardiomyopathy with latent obstruction.
abstract: BACKGROUND
  The purpose of this article is to describe the demographic and clinical features of patients with hypertrophic cardiomyopathy (HCM) and latent obstruction, with an emphasis on identifying factors associated with disease progression and survival. The presence of a resting left ventricular outflow obstruction in patients with HCM has been well described and is associated with increased symptoms and adverse long-term outcomes. However, less is known about patients with latent obstruction.
  
  
  METHODS
  Four hundred fifteen patients with echocardiographic or catheterization findings of latent obstruction, defined as a left ventricular outflow pressure gradient <30 mm Hg at rest, which increases to > or =30 mm Hg with provocation, were identified and included in the study group.
  
  
  RESULTS
  The mean age was 55.0 +/- 17.9, and 226 (54.6%) patients were male. There were 330 (79.5%) patients with New York Heart Association (NYHA) functional class I and II at baseline. Fifty-nine (17.9%) of these patients had symptom progression requiring septal reduction therapy. Eighty-five patients had severe symptoms (NYHA functional class III and IV) at baseline, and 23 (27.1%) underwent septal reduction. Overall survival at 1, 5, and 10 years was 98%, 91%, and 81%, respectively. Survival among patients after undergoing invasive relief of outflow obstruction was equivalent to the general US population.
  
  
  CONCLUSIONS
  Latent obstruction in HCM is an important pathophysiologic entity and may cause heart failure symptoms. One-third of patients in this referral series required invasive therapy for relief of symptoms. The evaluation of HCM patients with resting outflow tract gradients <30 mm Hg must include provocative maneuvers to identify this substantial subset of patients, preferably by physiologic exercise.
authors.affiliation: Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, MN, USA. jvaglio@yahoo.com
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Vaglio
authors.forename: Steve R
authors.initials: SR
authors.lastname: Ommen
authors.forename: Rick A
authors.initials: RA
authors.lastname: Nishimura
authors.forename: A Jamil
authors.initials: AJ
authors.lastname: Tajik
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Gersh
mesh_terms: D000704:Analysis of Variance; D006328:Cardiac Catheterization; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000209:etiology; D011379:Prognosis; D012189:Retrospective Studies; D016019:Survival Analysis; D014463:Ultrasonography; D014694:Ventricular Outflow Obstruction / Q000000981:diagnostic imaging / Q000209:etiology*