title: Supersensitive response to isoproterenol in patients with marked global reduction of cardiac metaiodobenzylguanidine uptake.
abstract: It is unknown whether the non-transplanted, denervated human heart is supersensitive to beta-adrenergic agonist in terms of inotropism and chronotropism. In the present study, 36 patients with normal left ventricular (LV) wall motion were divided into 3 groups according to the cardiac metaiodobenzylguanidine (MIBG) scintigrams: group I with normal MIBG uptake, group II with regionally reduced MIBG uptake, and group III with globally reduced MIBG uptake (heart-to-mediastinum ratio <1.6). Before isoproterenol (IP) infusion, heart rate (HR), blood pressure (BP) and echocardiographic indices were similar among the groups. There was a trend toward a greater increase in HR with IP (0.01 microg x kg (-1) x min(-1)) in group III (27+/-18 beats/min) than in groups I (20+/-8) and II (17+/-8) despite the lack of a significant difference in BP reduction by IP. During IP infusion, increases in posterior wall motion amplitude and LV fractional shortening were significantly greater in group III (4.5+/-1.8 mm and 16.4+/-5.4%, respectively) than in groups I (1.5+/-2.5 mm and 8.7+/-6.4%) and II (2.6+/-1.7 mm and 8.9+/-7.9%). The present results suggest that the sympathetically denervated human heart is supersensitive to IP and the exaggerated responses may be caused, at least in part, by a postsynaptic mechanism.
authors.affiliation: The Second Department of Internal Medicine, Toyama Medical & Pharmaceutical University, Toyama, Japan.
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Nozawa
authors.forename: Makoto
authors.initials: M
authors.lastname: Nonomura
authors.forename: Norio
authors.initials: N
authors.lastname: Igarashi
authors.forename: Bun-ichi
authors.initials: B
authors.lastname: Kato
authors.forename: Nozomu
authors.initials: N
authors.lastname: Fujii
authors.forename: Akihiko
authors.initials: A
authors.lastname: Igawa
authors.forename: Hidetsugu
authors.initials: H
authors.lastname: Asanoi
authors.forename: Hikaru
authors.initials: H
authors.lastname: Seto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inoue
mesh_terms: D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D004452:Echocardiography; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000294:innervation; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D013564:Sympathetic Nervous System / Q000503:physiopathology
chemical_list: D000318:Adrenergic beta-Agonists; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine; D007545:Isoproterenol