Clinical trials with hard outcome measures:
Such a trial was the Action to Control Cardiovascular Risk in Diabetes (ACCORD)， published in 2010. In the BP component of ACCORD [4]， subjects were randomized to systolic BP (SBP) targets of 120-139 mm Hg. (standard therapy) or <120 mm Hg (intensive therapy). The primary outcome measure was a composite of CV death， myocardial infarction (MI) or stroke. After a mean follow up of 4.7 years， the mean SBP in the standard and intensive groups were 133.5 and 119.3 mm Hg respectively， a difference of 14.2 mm Hg. The results were totally unexpected: there was no significant difference between the two groups for the primary outcome measure， or for CV death or MI (Fig. 5). There was a small but statistically significant benefit of the intensive therapy for stroke. This led the ACCORD investigators to conclude: “The results provide no evidence that the strategy of intensive BP control reduces the rate of a composite of major CV events in such patients”.
However， a different interpretation can be placed on these data. What is of particular interest is that the mean DBP in the intensive group was 60-65 mm Hg over the last 4 years of follow-up. Therefore， in terms of the lower limit of coronary autoregulation discussed above， the right question may not be “is intensive therapy beneficial?” but rather “is intensive therapy harmful?”， that is， was there an increased risk of CV events at these low DBPs? The answer， from ACCORD， is clearly no; in fact the incidence of the primary outcome， of non-fatal MI， and of a major coronary artery disease event was lower in the intensive group， but did not reach statistical significance. In addition， stroke was reduced in the intensive group， and this was statistically significant (Fig. 5).
Conclusion:
Does this mean that we should aim for <120/80 mm Hg in all our hypertensive patients? The evidence for stroke prevention is fairly solid， so that a patient who is felt to be at particular risk for stroke may be seriously considered to be appropriate for the lower BP target. A patient with coronary artery disease， or with a high risk of coronary artery disease (including those with diabetes)， may also be a suitable candidate for more intensive BP lowering. For all others the traditional <140/90 mm Hg target is acceptable [5].
References:
1. Vasan RS， Larson MG， Leip EP， et al. Impact of high normal blood pressure on the risk of cardiovascular disease. N Engl J Med. 2001;345:1291-1297.
2. Lewington S， Clarke R， Qizilbash N， et al. Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002;360:1903–1913.
3. Sipahi I， Tuzcu EM， Schoenhagen P， et al. Effects of normal， pre-hypertensive， and hypertensive blood pressure levels on progression of coronary atherosclerosis. J Am Coll Cardiol. 2006;48:833-838.
4. The ACCORD Study Group. Effects of intensive blood-pressure control in type 2 diabetes mellitus. N Engl J Med. 2010:362:1575-1585.
5. Rosendorff C， Black HR， Cannon CP， et al. AHA Scientific Statement. Treatment of hypertension in the prevention and management of ischemic heart disease. Circulation 2007;115:2761-2788.
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