Reproducibility of heart rate variability in patients with positive and negative head-up tilt test.

Ruiz G.A, Madoery C, Menéndez C, Tentori MC.

Hospital Fernández.
Buenos Aires. Argentina.

Abstract
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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