Idiopathic long QT syndrome with early afterdepolarization induced by epinephrine. Acase report.
A patient with idiopathic long QT syndrome had repeated syncopal episodes. The QTc interval on the electrocardiogram at rest was 530 ms and was prolonged by exercise up to 740 ms with T wave alternation. Intravenous epinephrine (0.1 microg/kg weight per min), but not isoproterenol (0.7 microg/min), produced early after depolarization of the monophasic action potential recorded at the right ventricular apex. Epinephrine prolonged the QTc interval to 710 ms. After the addition of propranolol to the epinephrine, the QTc (580 ms) was longer than at baseline. Methoxamine also prolonged the QTc to 580 ms. The QT interval in long QT syndrome is generally considered to be prolonged by a beta-adrenergic effect, but in the present case alpha-adrenergic stimulation had an additional effect on the prolongation of the QT interval.
Urao
Norifumi
N
Department of Cardiology, Kyoto Prefectural Yosanoumi Hospital, Japan. nori-u@f3.dion.ne.jp
Shiraishi
Hirokazu
H
Ishibashi
Kazuya
K
Hyogo
Masayuki
M
Tsukamoto
Masaki
M
Keira
Natsuya
N
Hirasaki
Satoshi
S
Shirayama
Takeshi
T
Nakagawa
Masao
M
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology / Q000627:therapeutic use; D004562:Electrocardiography / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000188:drug therapy* / Q000209:etiology; D008564:Membrane Potentials / Q000187:drug effects*; D008729:Methoxamine / Q000494:pharmacology / Q000627:therapeutic use; D008875:Middle Aged; D010375:Pedigree
D000316:Adrenergic alpha-Agonists; D008729:Methoxamine; D004837:Epinephrine