PREDICTIVE VALUE OF BLOOD-PRESSURE DIPPING AND SWINGING WITH REGARD TO VASCULAR-DISEASE RISK

This prospective 6-year follow-up study of 176 patients treated with a ntihypertensive drugs investigates the extent to which an excessive ci rcadian blood pressure (BP) amplitude (above the 90th percentile of ge nder- and age-matched peers) contributes to the risk of adverse vascul ar outcomes (coronary events, ischaemic stroke, renal failure and reti nal bleeding). The results are compared with those based on the standa rd deviation (SD) of BP and a measure of 'dipping' (night-time vs dayt ime BP difference). A relative risk invariably larger than unity is fo und for 'over-swingers', that is for patients with an excessive circad ian BP amplitude, and with one exception also for patients with an SD in the upper decile of the distribution, A classification of patients as dippers vs non-dippers does not detect any statistically significan t difference in the incidence of adverse vascular outcomes in the samp le investigated. A combination of ambulatory or manual BP monitoring a nd chronobiological data analysis and interpretation facilitates the d iagnosis of an excessive circadian BP amplitude and can serve to guide the timing of treatment, not only for lowering BP but also to reduce BP variability in particular, an excessive circadian amplitude. The la tter condition, and an SD in the upper decile of the distribution, in this order, were associated with the largest increase in risk for isch aemic stroke and nephropathy. The excessive circadian BP amplitude con stitutes an a priori no-win situation in the case of reliance upon con ventional casual measurements, since in this condition, the BP is elev ated only during part of the day. Thus, if casual BP measurements are taken when pressures are acceptable, the patient is likely to be left untreated, but would remain at a very high risk of developing vascular disease, Conversely, should the patient be examined when pressures ar e high, drugs may be prescribed that may lower the BP too much when gi ven at the wrong time when, unknowingly, pressures are already spontan eously low and may barely suffice for perfusion. Since some antihypert ensive drugs can reduce both BP and BP variability, further studies ar e required in order to examine whether treatment aimed at reducing an excessive circadian BP amplitude improves prognosis in subjects with h igh BP variability.