© 2004 by European Society of Cardiology
ORIGINAL ARTICLE
Impact of age and blood pressure on the lower arterial pressure limit for maintenance of consciousness during passive upright posture in healthy vasovagal fainters: preliminary observations*
Cardiac Arrhythmia Center, Department of Medicine (Cardiovascular Division), University of Minnesota Minneapolis, MN, United States
Maintenance of consciousness importantly depends on systemic arterial blood pressure (BP) remaining above the lower pressure limit for cerebrovascular autoregulation. This study evaluated the impact of age and baseline arterial blood pressure (BP) on the BP recorded at onset of syncope in otherwise healthy individuals undergoing passive head-up tilt (HUT) testing for suspected vasovagal syncope. Since hypertension is thought to shift the lower autoregulation point to higher values, and since older healthy patients tend to have higher BP than younger individuals, we hypothesized that even among healthy individuals HUT-induced syncope would occur at higher BP in older compared with younger subjects. Three groups of otherwise healthy individuals who had positive HUT were identified: Group 1: <25 years, n=17; Group 2: 2559 years, n=18; and Group 3:
60 years, n=7. As expected, baseline arterial systolic blood pressure of patients
60 years (162±37 mmHg) was significantly higher than in the other two groups (Group 1: <25 years, 116±15 mmHg; Group 2: 2559 years, 128±12 mmHg). Further, the
60 age group tolerated upright posture for a longer period before syncope than did younger patients. However, despite a trend for BP at syncope to increase with age, differences were small (Group 3:
60 years, 61±15 mmHg, Group 2: 2559 years, 58±6 mmHg, and Group 1: 54±16 mmHg) and were not statistically significant. Thus, in generally healthy individuals, age and baseline BP has only a minor effect on the lower limit of BP necessary for maintenance of consciousness. On the other hand, higher baseline BP provides older individuals a greater blood pressure reserve for maintenance of consciousness compared with younger subjects.
Key Words: syncope, cerebral autoregulation, head-up tilt testing
*Corresponding author. Tel.: +1-612-625-4401; fax: +1-612-624-4937. E-mail address: bendi001{at}umn.edu (D.G. Benditt).
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