Heart rate variability and its determinants in patients with severe or mild essential hypertension

How cardiac autonomic nervous control is related to the severity of essenti al hypertension in patients receiving long-term antihypertensive therapy is not well known. The aim of this study was to examine heart rate variabilit y (HRV), a non-invasive measure of cardiac autonomic function, in patients with long-term and medically treated mild and severe essential hypertension and healthy control subjects, and to assess the clinical determinants of H RV in these patients. Thirty-four patients with severe essential hypertensi on (SEHT) and 29 with mild essential hypertension (MEHT) as well as healthy age- and sex-matched control subjects were studied. HRV was assessed from 10 min ECG-recordings during paced (0.2 Hz) breathing at rest and expressed as time and frequency domain measures. In the SEHT group time (SDNN, RMSSD ) and frequency domain measures (total power, low-frequency (LF) power and high-frequency (HF) power of HRV in absolute units, and LF and HF power of HRV in normalized units) of HRV were significantly lower when compared with those of the control group. The MEHT and control groups did not differ fro m each other with respect to time or frequency domain measures of HRV. Comp arison between the hypertensive groups showed that SDNN, total power, LF po wer and HF power were lower in the SEHT group compared with the MEHT group (P <0.05 for all). Among hypertensive patients RR-interval, age, gender, sy stolic finger blood pressure and diastolic office blood pressure as well as 24-h blood pressure were significant determinants of HRV. In conclusion, w e found that the severity of chronic essential hypertension seems to be rel ated to the severity of impairment of cardiac autonomic control.