Background: Patients with essential hypertension (EH) and left ventricular hypertrophy (LVH) have an increased risk of cardio-vascular complications. Alterations in the autonomic nervous system (ANS) activity may play a role in the development of serious cardiac arrhythmias and mortality in these patients.
Aim: To examine the activity of ANS in patients with established EH in relation to the presence of LVH.
Methods: The study group consisted of 70 subjects: 50 patients with untreated EH (mean age 44.4+/-12.7 years, 28 patients without LVH and 22 with LVH), and 20 age-matched healthy volunteers. ANS reactivity was assessed using heart rate variability (HRV) analysed during tilt table testing at 60 degrees. The following 5-min time-periods were analysed: (A) before tilting (supine position), (B) initial period of tilting, (C) last 5 min of tilting, and (D) immediately after completion of tilt test (after return to supine position).
Results: Patients with EH without LVH had a higher increase of LF/HF values (period B versus period C) compared with controls (p<0.05). The change from tilt to supine position caused significantly lower change in lnHF values in patients with EH and LVH than in controls (p<0.01) or patients with EH without LVH (p<0.005). In patients with EH and LVH a significant correlation between HF and LVmass/height (r=-0.5, p<0.01) was noted. Compared with healthy controls, patients with EH and LVH had significantly lower HRV parameters [lnLF values were significantly lower in all analysed periods, (p<0.05), and lnHF - during period D, (p<0.01)] whereas LF/HF ratio assessed during period D was significantly higher (p<0.05).
Conclusions: In patients with EH without LVH a relative dominance of sympathetic activity is present. LVH in EH leads to a decrease in vagal drive and progressive inhibition of parasympathetic activity, both of which decrease HRV. These changes may play an important role in the electrical instability of hypertrophied myocardium.