title: Assessment of autonomic activity during daily life of patients with head-up tilt-induced prolonged asystole.
abstract: Autonomic activity is important in the pathophysiology of neurally mediated syncope (NMS) patients diagnosed by the head-up tilt (HUT) test, and prolonged systole induced by HUT is associated with a malignant vasovagal syndrome. This study investigated whether or not daily autonomic activity evaluated by heart rate variability (HRV) assessed through 24-hour ambulatory ECG monitoring was augumented in HUT-induced asystole (AS; > 30 s) and whether or not HRV differed between NMS patients with and without AS. Ambulatory ECG monitoring was performed in 176 patients with suspected NMS and in 62 age-matched healthy control subjects (C group, age: 36 +/- 13 yr), with HRV time and frequency domain indices measured within 48 hours of HUT. Six patients displayed prolonged AS (PAS group, age: 33 +/- 12 yr), and 109 patients had positive HUT (P group, age: 29 +/- 17 yr), while 61 patients had negative HUT (N group, age: 40 +/- 18 yr). Several HRV indices in the P group were higher than those in the N and C groups. However, HRV indices did not differ between the P group and the PAS group. It is concluded that impairment of autonomic activity specifically related to orthostatic stress could be important in the pathophysiology of HUT-induced prolonged asystole, while impairment of autonomic activity in daily life is not as important in NMS patients with HUT-induced prolonged asystole.
authors.affiliation: National Defense Medical College Research Institute, Division of Biomedical Engineering, 3-2, Namiki Tokorozawa City, Saitama 359-8513, Japan. dui1577@db3.so-net.ne.jp
authors.forename: Bonpei
authors.initials: B
authors.lastname: Takase
authors.forename: Takashi
authors.initials: T
authors.lastname: Akima
authors.forename: Kimio
authors.initials: K
authors.lastname: Satomura
authors.forename: Takemi
authors.initials: T
authors.lastname: Mastui
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Ohsuzu
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ishihara
authors.forename: Akira
authors.initials: A
authors.lastname: Kurita
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D015716:Electrocardiography, Ambulatory / Q000379:methods; D005260:Female; D006323:Heart Arrest / Q000209:etiology* / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007564:Japan; D008297:Male; D018579:Patient Selection; D011187:Posture / Q000502:physiology*; D013575:Syncope / Q000175:diagnosis / Q000503:physiopathology; D018667:Tilt-Table Test / Q000379:methods*; D013997:Time Factors