Background: The aim of the study was to evaluate whether there are any significant differences in cardiac autonomic regulation in distinct types of hypertensive cardiac remodelling.
Material/Methods: We examined 86 patients with mild to moderate essential hypertension (EH). The parameters of left ventricle (LV) were measured by echocardiography: the diastolic mass normalized for body surface area (LVMI) and relative wall thickness (RWT). All patients were divided into three groups: normal LV geometry (23), concentric left ventricular hypertrophy (LVH) (29) and eccentric LVH (34). The control group included 30 age and sex-matched healthy volunteers. For calculation of heart rate variability (HRV) 512 RR intervals in supine rest and passive tilt were measured. Power spectral analysis with fast Furrier transform was used to obtain the total power, low frequency (LF) power (from 0.003 to 0.14 Hz), high frequency (HF) power (from 0.15 to 0.40 Hz) and sympathovagal index (SVI) as LF: HF ratio.
Results: The parameters of HRV did not differ significantly among the groups studied. In the group with normal LV geometry there was observed a good response to tilt test resulting in an increase of SVI in three times (from 2.4&plusm;0.3 to 7.2&plusm;0.4), while in patients with both types of LVH there were no significant changes in SVI or even an inverse reaction to passive tilt. In the group with normal geometry patients with higher meanings of RWT had higher LF power (r&eguals;0.52, p<0.01), while in patients with LVH the increasement of LVMI and RWT was associated with reduction of HRV (rr&eguals;-0.43, -0.36, p<0.05, respectively).
Conclusions: Heart rate variability is significantly reduced in essential hypertension and is also closely connected with cardiac structure and function. Patients with normal LV geometry are characterized by a preserved response to tilt test. LVH produce significant disturbances of autonomic regulation possibly due to lower sensitivity of cardiac adrenoreceptors independently of the LVH pattern.

Keywords: essential hypertension, left ventricular hypertrophy, heart rate variability, autonomic regulation