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Reproducibility of heart rate variability in patients with positive and negative head-up tilt test.
Ruiz G.A, Madoery C, Menéndez C, Tentori MC.
Buenos Aires. Argentina.
In order to evaluate the reproducibility of heart rate variability (HRV) in frequency domain analysis during head-up tilt test (TT) in patients with syncope, two TT (75°, 45 min) were performed in 30 patients (pts). Both studies were positive in 8 pts (GI, 21.6±7 years), negative in 12 pts (GII, 34±16 years), whereas 10 had one positive and one negative test (GIII, 39.2±20 years). The HRV was recorded in short duration steps (5min) in supine position (baseline) and at 5, 15 and 30 min. The following parameters of HRV were analyzed: high frequency (HF, 0.15-0.4Hz), low frequency (LF, 0.04-0.15 Hz) and low/high ratio (L/H). The values of the first and the second study were compared at baseline (b), 5 min into the TT and a) the last record before the onset of symptoms(BS) in TT+ vs its equivalent in TT- or b) 15 into the test (GII). Results are shown as the HF and LF logarithms (mean), L/H ratio (mean). CC: correlation coefficient between studies.* P<0.05.
Neither the HF and LF power spectra nor the L/H ratio show significant differences between the first and second study, regardless of the TT outcome. Patients who do not replicate the response to TT, nevertheless have a high correlation of the HRV parameters.
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