Heart rate variability in white-coat hypertension

Abstract

The objective of this study was to compare heart rate variability (HRV) in patients with essential hypertension, in patients with white-coat hypertension and in normotensive control individuals, and to investigate a possible relation between HRV and vasoactive hormones. Patients with essential hypertension (n=19, 61 years, median and interquartile range: 40-66 years), patients with white-coat hypertension (n=8, 52 years, median and interquartile range: 41-64 years) and normotensive participants (n=13, 50 years, median and interquartile range: 39-57 years) participated in the study. HRV was measured at rest in the supine position, during standing and during controlled forced breathing (respiration frequency >20/min). Power spectral density was calculated using Fourier transformation. Controlled breathing caused a decrease in low frequency (LF) variation and LF/high frequency variation (LF/HF) in all blood pressure groups. The decrease in LF was smaller in the hypertensive group (-60 ms2) than in the normotensive group (-139 ms2) (P=0.03; hypertensive group vs. normotensive group). The decrease in LF/HF induced by controlled breathing was -0.9 ms in the hypertensive group, -2.0 ms2 in the white-coat hypertensive group and -2.8 ms2 in the normotensive group, (P=0.037; hypertensive group vs. normotensive group). We found a positive correlation between baseline plasma renin concentration and LF (r=0.330, P=0.037) and LF/HF (r=0.378, P=0.016) at rest. The observed differences in HRV might reflect the impaired responsiveness to autonomic challenge in hypertensive patients. We did not find the HRV spectrum in white-coat hypertension different from the HRV spectrum in hypertension or normotension.