title: Changes in cardiac autonomic activities in patients with syndrome X. A study of spectral analysis of heart rate variability.
abstract: The present study was designed to assess cardiac autonomic activities, coronary microvascular function, and their relationship in patients with syndrome X. Control of coronary blood flow is complex, and impaired coronary flow reserve has been attributed as the cause of myocardial ischemia in patients with syndrome X. It is unknown whether cardiac autonomic activities are altered in the presence of coronary microvascular dysfunction in patients with syndrome X. Eighteen patients with syndrome X were studied. Great cardiac vein flow was measured by the thermodilution method and the coronary flow reserve was determined by intravenous dipyridamole (0.56 mg/kg) infusion. Twenty-four-hour ambulatory electrocardiograms were obtained in a drug-free state. Another 14 age- and sex-matched normal subjects served as a control group. The amplitude (in ms) of ultralow (ULF), very-low (VLF), low (LF), and high (HF) frequency bands and total spectra of heart rate variability were measured for twenty-four-hour and every four-hour interval of the day.
authors.affiliation: Department of Medicine, National Yang-Ming University, School of Medicine, Taichung, Taiwan, Republic of China.
authors.forename: W L
authors.initials: WL
authors.lastname: Lee
authors.forename: J W
authors.initials: JW
authors.lastname: Chen
authors.forename: C W
authors.initials: CW
authors.lastname: Kong
authors.forename: J J
authors.initials: JJ
authors.lastname: Wang
authors.forename: C T
authors.initials: CT
authors.lastname: Ting
authors.forename: W L
authors.initials: WL
authors.lastname: Chan
authors.forename: S P
authors.initials: SP
authors.lastname: Wang
authors.forename: M S
authors.initials: MS
authors.lastname: Chang
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology*; D003326:Coronary Circulation / Q000502:physiology*; D015716:Electrocardiography, Ambulatory; D005080:Exercise Test; D005260:Female; D006329:Heart Conduction System / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D017566:Microvascular Angina / Q000503:physiopathology*; D008875:Middle Aged