Comparative Study Of Blood Pressure Variability And The Importance Of Blood Pressure Variability In Vascular Damage

Part â… Comparative study of blood pressure variability in SHR and SHR-SPAim: To obtain genomic information on blood pressure variability (BPV), one of the strategies is to use linkage analysis in segregating populations produced by crossbreeding of inbred strains. We demonstrated and compared BPV, as well as other hemodynamic phenotypes such as blood pressure (BP), and baroreflex sensitivity (BRS) in genetic hypertensive rats to find out which animal is more appropriate as a parental strain in our BPV linkage studies. And as little is known about the BPV of SHR-SP, we also wonder if its BPV is higher than SHR in parallel with their BP changes.Methods: BP was recorded continuously in conscious, freely moving rats using a computerized technique. BPV was expressed as the standard deviation of beat-to-beat BP values during a 1-h period. BRS was determined by measuring the heart period prolongation in response to the elevation in BP produced by an intravenous injection of phenylephrine.Results: Body weight and heart period were not different between spontaneously hypertensive rats (SHR) and stroke- prone spontaneously hypertensive rats (SHR-SP) at the age of 15 weeks. The BP level was markedly higher in SHR-SP than SHR, whereas there were no significant differences in BPV and BRS. Quantitatively, systolic, diastolic and mean BP were significantly elevated by 36.9%, 42.9% and 39.5%, respectively, in SHR-SP compared with SHR (P < 0.01). However, their variabilities were elevated only by 14.0%, 0.4% and 10.1%, respectively, without statistical significance (P > 0.05).Conclusion: BPV and BRS were not changed in parallel with the BP alterationsin SHR and SHR-SP. And As far as we know, this is the first report about the BPV of SHR-SP. Considering the shorter life span of SHR-SP (about 45weeks) compared with SHR (about 75 weeks) we concluded that SHR was more suitable than SHR-SP for crossbreeding in BPV linkage studies. Our study also provided a new good example to delineate that BPV is not necessarily dependent on BP level.Part IIThe importance of blood pressure variability in vascular damageBlood pressure (BP) level is a well-known determinant for the cardiovascular damage in hypertensive patients and animals, and BP reduction has been emphasized to be important for cardiovascular protection. However, it is certainly not the unique determinant for cardiovascular damage. A lot of researches have shown that blood pressure variability (BPV), which is defined by the extent of the variation in BP, is a novel risk factor for end-organ damage, including vascular damage.Aim: The present study was designed to determine how important the novel risk factor of elevated BPV is in the determination of vascular damage by comparison with the classic risk factor of a high BP.Methods and results: The effects of haemodynamics on vascular morphology were evaluated by univariate and multivariate regression analysis in male sham-operated and sinoaortic-denervated Wistar-Kyoto rats and spontaneously hypertensive rats (n =34), with an enlarged distribution of haemodynamics. BPV was more important than BP for aortic hypertrophy, and almost equal to BP for the remodeling of tissue arterioles, indicated by the change in WT/ID.Conclusion: BPV is a critical and independent risk factor involved in vascular damage, which is more important than BP for aortic hypertrophy. Therefore, BPV control will be much beneficial to vascular protection, from the view of therapeutics.