title: Sublingual isosorbide dinitrate for the detection of obstruction in hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  Hypertrophic cardiomyopathy (HCM) is predominantly associated with left ventricular outflow tract (LVOT) obstruction. The assessment of the obstruction with a provoking test should be a routine part of HCM evaluation. The aim of the study was to determine the utility of a sublingual spray application of isosorbide dinitrate (ISDN) for detection of an obstruction.
  
  
  RESULTS
  We have prospectively analysed 77 consecutive HCM patients, measuring the LVOT gradient at rest, using the sublingual spray application of ISDN (2.5 mg; after 2, 5, and 10 min), and with exercise echocardiography. An obstruction was defined as a gradient ≥ 30 mmHg. An obstruction was present in 15 patients (19%) at rest, in 42 patients (55%) after ISDN, and in 55 patients (71%) after exercise. The ISDN test had a sensitivity of 76% and the specificity of 100% relative to exercise echocardiography, while at-rest measurements had a sensitivity of 27% and a specificity of 100%. The chronological difference in the prevalence of obstructions during the ISDN test was statistically significant (P < 0.05); at ISDN plus 2 min, obstructions were seen in only 29 patients (38%, gradient 28.8 ± 25.0 mmHg), however, at ISDN plus 5 and 10 min, obstructions were found in 42 patients (55%, gradient 44.5 ± 39.6 mmHg).
  
  
  CONCLUSIONS
  The ISDN test is a reliable screening method for the detection of an HCM obstruction, however, the measurement should be delayed 5-10 min after the application of ISDN. Patients with negative ISDN tests should undergo exercise echocardiography.
authors.affiliation: Department of Cardiology, University Hospital Motol, First and Second Medical School of Charles University, V Uvalu 84, 150 21 Prague, Czech Republic. zejada@seznam.cz
authors.forename: David
authors.initials: D
authors.lastname: Zemánek
authors.forename: Pavol
authors.initials: P
authors.lastname: Tomasov
authors.forename: Stanislava
authors.initials: S
authors.lastname: Homolová
authors.forename: Katerina
authors.initials: K
authors.lastname: Linhartová
authors.forename: Josef
authors.initials: J
authors.lastname: Veselka
mesh_terms: D000286:Administration, Sublingual; D002312:Cardiomyopathy, Hypertrophic / Q000503:physiopathology*; D025401:Echocardiography, Stress; D005080:Exercise Test; D005260:Female; D006801:Humans; D007548:Isosorbide Dinitrate / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D014665:Vasodilator Agents / Q000008:administration & dosage; D014694:Ventricular Outflow Obstruction / Q000150:complications / Q000000981:diagnostic imaging*
chemical_list: D014665:Vasodilator Agents; D007548:Isosorbide Dinitrate