title: Head-up tilt testing with different nitroglycerin dosages: experience in elderly patients with unexplained syncope.
abstract: OBJECTIVE
  Protocols using sublingual nitrates have been increasingly used to improve diagnostic accuracy of head-up tilt testing (HUT). Nevertheless, exaggerated responses to nitrates have been frequently described, particularly in elderly patients. The aim of this article is to evaluate, in an elderly population with unexplained syncope, whether the impact of sublingual nitroglycerin (NTG) used as a provocative agent is dose-dependent.
  
  
  RESULTS
  One hundred and twenty consecutive elderly patients submitted to HUT using NTG after an asymptomatic drug-free phase were studied. Patients were divided into three groups according to the NTG dosage: 500, 375 and 250 microg. The test was considered positive when there was reproduction of symptoms with bradycardia and/or arterial hypotension. A gradual decrease in the blood pressure after NTG was considered an exaggerated response to nitrates. There were no differences in the clinical characteristics of the different subgroups. A positive test was obtained in 50% of the patients in each group. The rate of exaggerated responses was identical in all groups and ranged between 15 and 17%.
  
  
  CONCLUSIONS
  In an elderly population with syncope of unknown origin submitted to HUT, the response to NTG is not dose-dependent, and no difference was found in the rate of exaggerated responses to nitrates with different NTG dosages.
authors.affiliation: Cardiology Department, Santa Marta Hospital, R. Santa Marta, 1169-024 Lisboa, Portugal. ana_timoteo@yahoo.com
authors.forename: Ana Teresa
authors.initials: AT
authors.lastname: Timoteo
authors.forename: Mario Martins
authors.initials: MM
authors.lastname: Oliveira
authors.forename: Joana
authors.initials: J
authors.lastname: Feliciano
authors.forename: Eduardo
authors.initials: E
authors.lastname: Antunes
authors.forename: Manuel Nogueira
authors.initials: MN
authors.lastname: da Silva
authors.forename: Sofia
authors.initials: S
authors.lastname: Silva
authors.forename: Sofia
authors.initials: S
authors.lastname: Santos
authors.forename: Rui
authors.initials: R
authors.lastname: Ferreira
mesh_terms: D000368:Aged; D004305:Dose-Response Relationship, Drug; D005260:Female; D018475:Head-Down Tilt; D006801:Humans; D008297:Male; D005996:Nitroglycerin / Q000008:administration & dosage*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013575:Syncope / Q000175:diagnosis*; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin