Frequency shift in baroregulatory oscillation in borderline hypertensive subjects.

The aim of this study was to quantify the frequency shift in vasomotor oscillations in blood pressure we observed in borderline hypertensive individuals in our previous study. Electrocardiogram and intraarterial blood pressure were recorded in 33 normotensive, 29 borderline hypertensive, and 33 mildly hypertensive men (aged 35 to 45 years). Five-minute stationary periods in supine, sitting, and standing positions, and during sleep were extracted from the recordings for autoregressive frequency domain analysis. In borderline hypertensive subjects vasomotor oscillations in the range of 0.05 to 0.12 Hz in blood pressure and heart rate, assumed to be associated with baroreceptor activity, were shifted to lower values as compared with the other two groups. The frequency shift was assessed by median frequency of the oscillations. Significant between-group differences were observed in the supine and sitting positions. No significant between-group differences were seen in normalized spectral power estimates. Further studies are required to determine whether the frequency shift provides prognostic information on cardiovascular morbidity.