title: Age, hypertension, and cardiac responses to beta-agonist in humans.
abstract: OBJECTIVE
  To evaluate the effects of hypertension on heart rate and left ventricular responses to beta-agonist in young and older subjects, as well as the modulating effect of the arterial baroreflex on these responses.
  
  
  METHODS
  Isoproterenol (INN, isoprenaline) alone was infused in 14 young normotensive subjects (mean age, 30 +/- 2 years), 18 older normotensive subjects (mean age, 60 +/- 2 years), 11 young hypertensive subjects (mean age, 36 +/- 1 years), and 17 older hypertensive subjects (mean age, 59 +/- 1 years); isoproterenol combined with ganglionic blockade (trimethaphan [INN, trimetaphan]) was administered to eight young normotensive subjects and eight young hypertensive subjects. Isoproterenol was infused at three to four incremental rates, each rate for 8 minutes. Left ventricular responses were assessed by echocardiography.
  
  
  RESULTS
  Isoproterenol caused similar increases in heart rate in all four groups. With ganglionic blockade, heart rate responses were enhanced but were similar in the young normotensive and hypertensive subjects. In young subjects, hypertension did not affect left ventricular responses to isoproterenol alone, whereas older hypertensive subjects showed some blunting of left ventricular responses compared with older normotensive subjects. With ganglionic blockade, young hypertensive subjects also showed mild blunting of left ventricular responses.
  
  
  CONCLUSIONS
  These results show that, in humans, hypertension does not lead to a decrease in chronotropic responses to infusion of the beta-agonist isoproterenol and causes only a modest decrease in left ventricular responses.
authors.affiliation: Division of Cardiology, University of Ottawa Heart Institute, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: White
authors.forename: A
authors.initials: A
authors.lastname: Fourney
authors.forename: F H
authors.initials: FH
authors.lastname: Leenen
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D002395:Catecholamines / Q000097:blood; D004359:Drug Therapy, Combination; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D007262:Infusions, Intravenous; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome; D014294:Trimethaphan / Q000494:pharmacology*; D016277:Ventricular Function, Left / Q000187:drug effects*
chemical_list: D000318:Adrenergic beta-Agonists; D000959:Antihypertensive Agents; D002395:Catecholamines; D014294:Trimethaphan; D007545:Isoproterenol