title: Variability of left ventricular outflow tract gradient during cardiac catheterization in patients with hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  This study characterizes left ventricular outflow tract (LVOT) gradient variability in patients with hypertrophic cardiomyopathy (HCM) during cardiac catheterization.
  
  
  BACKGROUND
  Management of HCM is directed by the presence and magnitude of LVOT obstruction. The magnitude and clinical impact of spontaneous variability during a single cardiac catheterization has not been described.
  
  
  METHODS
  Fifty symptomatic patients with HCM (mean age 55 ± 15 years; 48% men) underwent cardiac catheterization with high-fidelity, micromanometer-tip catheters and transseptal measurement of left ventricular pressures. Obstruction was defined as resting LVOT gradient ≥ 30 mm Hg and severe obstruction as ≥ 50 mm Hg. Variability in LVOT gradient was calculated as the difference of the largest and smallest LVOT gradients in the absence of provocative maneuvers or interventions.
  
  
  RESULTS
  The largest LVOT gradient was 54.6 ± 56.4 mm Hg. The spontaneous variability in LVOT gradient was 49.0 ± 53.1 mm Hg (range 0 to 210.8 mm Hg, median 15 mm Hg). Discrepant classification of resting LVOT gradient severity was possible in 25 patients (50%). Twenty patients (40%) with severe obstruction could have been misclassified with regard to obstruction severity.
  
  
  CONCLUSIONS
  In patients with HCM, the LVOT gradient fluctuates significantly during a single hemodynamic assessment. Spontaneous variability could lead to misclassification of obstruction severity in one-half of studied patients. The dynamic nature of LVOT obstruction must be considered when assessing resting hemodynamics or the success of a given intervention during cardiac catheterization.
authors.affiliation: Divisions of Cardiovascular Diseases and Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Geske
authors.forename: Paul
authors.initials: P
authors.lastname: Sorajja
authors.forename: Steve R
authors.initials: SR
authors.lastname: Ommen
authors.forename: Rick A
authors.initials: RA
authors.lastname: Nishimura
mesh_terms: D001011:Aorta / Q000473:pathology*; D006328:Cardiac Catheterization; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy; D003657:Decision Making; D005260:Female; D006305:Health Status Indicators; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D011379:Prognosis; D018709:Statistics, Nonparametric; D013997:Time Factors; D014694:Ventricular Outflow Obstruction / Q000209:etiology / Q000473:pathology*