ABC | Volume 110, Nº4, April 2018

Original Article Silva et al Postural hypotension: spectral analysis Arq Bras Cardiol. 2018; 110(4):303-311 Figure 3 – Spectral analysis of a female patient (62 years of age) without orthostatic hypotension in supine position. RR: number of QRS in sinus rhythm; VLF: very low frequency; LF: low frequency; HF: high frequency; HFnu: HF normalized unit. 10000 7500 2500 5000 0 0.0 0.1 0.2 0.3 0.4 0.5 Frequency (c/b) Duration: 5 min Total RR: 366 corrected: 0 RR average: 820 ms 73 bpm Total potential: 484 VLF Power: 205 (0.00–0.04)Hz LF Power: 233 (0.04–0.15)Hz LFnu: 83.5 HF Power: 35 (0.15–0.40)Hz HFnu: 12.4 LF/HF: 6.75 Figure 2 – Spectral analysis of a male patient (67 years of age) with orthostatic hypotension (same of Figure 1) in orthostatic position, showing a decrease in low frequency (LF) component and in the LF/high frequency (HF) ratio, in relation to supine position. RR: number of QRS in sinus rhythm; VLF: very low frequency; HFnu: HF normalized unit. 26 K 19 K 13 K 6 K 0 0.0 0.1 0.2 0.3 0.4 0.5 Frequency (c/b) Duration: 5 min Total RR: 280 corrected: 0 RR average: 1074 ms 56 bpm Total potential: 2424 VLF Power: 1828 (0.00–0.04)Hz LF Power: 342 (0.04–0.15)Hz LFnu: 57.5 HF Power: 244 (0.15–0.40)Hz HFnu: 41.0 LF/HF: 1.40 of BP and HR. Increases in norepinephrine plasma levels, decreased sensitivity of beta-adrenergic receptors, decreased vasomotor response mediated by alpha receptors, and reduced baroreflex response and parasympathetic tone contribute to the occurrence of OH in the elderly. 8,9 Therefore, while approximately 5% of middle-aged adults have OH, 16 the prevalence increases to nearly 41% in those aged 80 years or older. 6 In the present study, patients with and without OH were age-matched and all of them were younger than 60 years, and hence results were not affected by age. Previous studies have shown different results in the prevalence of OH and its association with gender, according to age and study setting. In a study conducted in the 90’s decade, Rutan et al. 17 evaluated a population of 5,201 elderly subjects (≥65 years), with an OH prevalence of 18.2% and no difference between the sexes. In patients hospitalized for OH, the prevalence was higher in men (55.3% in the age range of 65 – 74 years), although 54% of patients aged 75 years or older were women, with a total of 15,858 admissions for OH in a year. 18 In our population, there was a predominance of men in the group of patients with OH; however, Spearman’s correlation coefficient was 0.27, i.e., of small magnitude, which suggest that there was no statistical difference in sex between the groups. Also, sex was not an OH predictor in multivariate analysis. Studies have demonstrated the importance of rises in HR in the orthostatic position, its association with increased sympathetic activity and higher orthostatic tolerance. 19 Nevertheless, the role of HR in the supine position in OH patients has not been well established yet. Changes in autonomic tone 13 and sinus node 307