Autonomic modulation in hypertension without hypertrophy

Cardiac autonomic modulation and baroreflex sensitivity are altered in individuals with essential hypertension. Hypertension is considered as a strong and independent risk factor for supraventricular and ventricular arrhythmias. The aim of the present study was to evaluate cardiac autonomic control and the arrhythmogenic risk by using 24-h heart rate variability (HRV) and heart rate turbulence (HRT) analysis in essential hypertension without left ventricular hypertrophy (LVH).

Fifty-eight newly diagnosed untreated hypertensive patients without LVH (mean age 51 ± 12 years, 26 women) and 56 adult, healthy volunteers (mean age 49 ± 12 years, 24 women) were included in the study. Subjects with secondary causes of hypertension or autonomic dysfunction were excluded. The diagnosis of hypertension was based on ambulatory blood pressure monitoring results. Time-domain HRV parameters and HRT parameters were calculated from 24-hour Holter recordings.

Values of SDNN and SDANN in the hypertension group were significantly lower than in the control group (P < 0.01 and P < 0.01, respectively). At least one of the turbulence onset (TO) and turbulence slope (TS) values were found abnormal in 10 of 32 hypertensive patients and in 5 of 24 control individuals (P = 0.38). There was no significant difference between HRT parameters, TO and TS (P = 0.67 and P = 0.12, respectively).

Sympathetic tone begins to increase in hypertension before LVH develops. However, the impact of this increase on HRT is not clear. There is a need for further research to investigate the impact of hypertension and LVH on HRT.