Key result
Age, not the head-up tilt test response, is the major determinant of autonomic behavior during early HUT, with young patients significantly increasing sympathovagal balance unlike the elderly.
Why the study?
Does age or head-up tilt test outcome determine autonomic behavior (HRV) during early head-up tilt test in patients with syncope?
Observational (n=102)
Does age or head-up tilt test outcome determine autonomic behavior (HRV) during early head-up tilt test in patients with syncope?
Age, rather than the head-up tilt test outcome, is the major determinant of autonomic behavior (heart rate variability) during early head-up tilt testing in patients with syncope.
Age warrants consideration when interpreting early HUT autonomic changes in syncope; leaves open whether tilt response adds independent value.
The study of autonomic behavior during a head-up tilt test (HUT) has been deemed important to understand the loss of consciousness mechanism. Though HRV in patients with HUT(+) and HUT(-) has been compared, few trials emphasized the importance of age. HRV in frequency domain was analyzed based on 5-minute samples in the supine position, and between 5 and 10 minutes during early tilt test (R1) in 102 patients with one or more episodes of syncope (mean age 44.3 +/- 20.8, range 15-85 years, 55 women). Two subgroups were selected afterwards: (1) young patients between 15 and 35 years of age (41 patients) and (2) elderly patients aged 60 or more (36 patients). The following parameters were taken into account: the sum of low (LF) and high frequency (HF) (LF and HF in absolute values and in normalized units), the LF/HF ratio (L/H ratio), and the percentage of change between baseline and R1 values. The HRV behavior in young and elderly patients with positive and negative HUT was established. We then analyzed the correlation between HRV and age and HUT outcome. A multiple regression analysis encompassing age, HUT outcome, gender, and number of syncope episodes was performed. In young patients, the LF and HF areas and the L/H ratio changed significantly between baseline and R1. The L/H ratio increases from baseline to R1. Conversely, these differences were not significant in the elderly. No differences between HUT(+) and HUT(-) within the same age group were observed. Age related significantly to practically all HRV parameters analyzed, whereas the tilt test outcome correlates poorly with HF normalized units and LF normalized units during R1, and the L/H ratio changes between baseline and R1. By means of a multivariate analysis, only age shows a significant correlation with the HRV values. Despite an all age triggering of vasovagal syncope during HUT, the young and elderly patients' autonomic behavior differs. The young considerably increase their sympathovagal balance during HUT, whereas the elderly have a mitigated autonomic response. No significant differences were observed during the first minutes of the test between those with a HUT(+) and those with a HUT(-) within the same age group. Age, and not the HUT response, is the major determinant of the autonomic behavior during early HUT.
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Ruiz et al. (2000) conducted an observational in Syncope (n=102). Head-up tilt test (HUT) vs. Age groups (15-35 vs ≥60 years) and HUT outcome (+ vs -) was evaluated on Heart rate variability (HRV) parameters (LF, HF, L/H ratio) during early tilt test. Age, not the head-up tilt test response, is the major determinant of autonomic behavior during early HUT, with young patients significantly increasing sympathovagal balance unlike the elderly.
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