Spectral coherence between blood pressure and inter-beat intervals in hypertension.

Continuous registration of blood pressure (BP) was obtained in 31 normotensives and 76 hypertensives (divided into 3 stages of hypertension) by a method where the blood pressure in a human finger was measured non-invasively in a beat-by-beat fully calibrated manner. From this signal, the power density spectra of inter-beat intervals (IBI), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were derived. Total spectral power (TP) and low/high spectral frequency ratios of all spectra were calculated. Cross-correlation analysis between IBI, SBP and DBP spectra showed that the level of amplitude and phase spectral coherence (SC) was strongly dependent of the stage of hypertension. SC was calculated by means of appropriate mathematical algorithms. Multiple step regression analysis pointed out that the observed phenomenon is highly significant for both--the amplitude and the phase SC (p < 0.01).

Relationship between heart rate variability and hypercholesterolaemia.

A statistically significant correlation between chronic (tonic) distress (expressed by long-term depression of heart rate variability-HRV) and the increase of the serum lipid level was found in the experimental group (39 clinically healthy subjects with hypercholesterolaemia; 16 women and 23 men; mean age 42.4 +/- 2.45 years). A statistically significant relationship was found also between the experimental and control group (39 healthy normocholesterolaemic subjects; 18 women and 21 men; mean age 43.7 +/- 2.18 years) when comparing distress indicating HRV-based measurements. Significant predictors of HRV depression were: total cholesterol and low-density lipoprotein cholesterol. The effect of a 3-month special diet served to 17 subjects selected from the experimental group led to a decrease of serum lipids but did not influence substantially HRV parameters. It can be concluded that HRV parameters reflecting stress reaction correlate with atherogenic serum lipids; their separate follow-up (which is quicker, easier and cheaper) can be used for prediction of cardiovascular health risk and probably for disorders in serum lipid metabolism.