Asymmetric features of short-term blood pressure variability.

Prolongations of cardiac cycles have a significantly larger contribution to short-term heart rate variability than shortenings--this is called heart rate asymmetry. Our aim is to establish the existence of blood pressure asymmetry phenomenon, which has not been done so far. We used 30-min resting continuous recordings of finger pressure waveforms from 227 healthy young volunteers (19-31 years old; 97 female), and performed Poincaré plot analysis of systolic blood pressure (SBP) to quantify the effect. Median contribution of SBP increases (C(i)) to short-term blood pressure variability was 52.8% (inter-quartile range: 50.9-55.1%) and median number of SBP increases (N(i)) was 48.8% (inter-quartile range: 47.2-50.1%). The C(i)>50% was found in 82% (P<0.0001; binomial test) and N(i)<50% in 75% (P<0.0001) of the subjects. Although SBP increases are significantly less abundant than reductions, their contribution to short-term blood pressure variability is significantly larger, which means that short-term blood pressure variability is asymmetric. SBP increases and reductions have unequal contribution to short-term blood pressure variability at supine rest in young healthy people. As this asymmetric behavior of blood pressure variability is present in most of the healthy studied people at rest, it can be concluded that blood pressure asymmetry is a physiological phenomenon.