title: The child with recurrent syncope: autonomic function testing and beta-adrenergic hypersensitivity.
abstract: Recurrent syncope in the child with a normal heart poses both diagnostic and therapeutic problems. To assess autonomic contributions to syncope, formal autonomic function testing was performed in 22 children (aged 7 to 18 years) with recurrent syncope and a normal heart. Autonomic testing consisted of eight to nine separate tests; 14 of the 22 patients had reproduction of syncope or symptoms during testing. Patients with a positive test had a lower norepinephrine level while supine (334 +/- 86 versus 547 +/- 169 pg/ml, p less than 0.01) and lower norepinephrine level in the upright position (628 +/- 219 versus 891 +/- 270 pg/ml, p less than 0.05) than did patients with a negative test. The slope of heart rate response versus log isoproterenol dose was greater in patients with a positive test than in those with a negative test (1.70 +/- 0.70 versus 0.89 +/- 0.19, p less than 0.01). All five patients with a positive test who were given intravenous propranolol had elimination of syncope with repeat testing. Eight of 10 patients with a positive test were successfully treated with atenolol, including 2 patients without prior resolution of symptoms after pacemaker implantation for symptoms attributed to bradycardia. Beta-adrenergic hypersensitivity may cause recurrent syncope in young patients. Inappropriate heart rate response to standing may elicit the Bezold-Jarisch reflex, resulting in bradycardia or hypotension, or both, in some patients. Beta-adrenergic blockade is of benefit in many of these patients.
authors.affiliation: Department of Pediatric, Baylor College of Medicine, Texas Children's Hospital, Houston.
authors.forename: J C
authors.initials: JC
authors.lastname: Perry
authors.forename: A
authors.initials: A
authors.lastname: Garson
mesh_terms: D000293:Adolescent; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D001262:Atenolol / Q000627:therapeutic use; D001341:Autonomic Nervous System / Q000503:physiopathology*; D002648:Child; D004837:Epinephrine / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007545:Isoproterenol; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011187:Posture; D011433:Propranolol / Q000627:therapeutic use; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D012008:Recurrence; D013575:Syncope / Q000097:blood / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology*
chemical_list: D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; D001262:Atenolol; D011433:Propranolol; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine