生物文献

EDITORIAL Rebecca F.Gottesman, MD,PhD

John Chalmers,MD, PhD Correspondence to

Dr.Gottesman:

rgottesm@https://www.360docs.net/doc/9616244951.html, Neurology?2014;82:1018–1019

See page1027Blood pressure and cerebral ischemia

A continuing dilemma

Classical neurologic teaching suggests that a higher cere-

bral systemic blood pressure(BP)be targeted for individ-

uals with occlusive carotid disease,in order to improve

cerebral perfusion through collaterals.This conflicts,

however,with observational population-based studies

and clinical trials supporting better outcomes associated

with lower BPs.In this issue of Neurology?,Powers

et al.1evaluate nonsurgical controls from the Carotid

Occlusion Surgery Study(COSS)and report lower rates

of stroke recurrence in individuals maintained at a

follow-up BP of130/85mm Hg or lower.

In COSS,195individuals with recent symptomatic

internal carotid artery occlusion and PET data demon-

strating increased ipsilateral oxygen extraction fraction

were randomized to superficial temporal artery–middle

cerebral artery bypass with medical management vs

medical management alone.The study was stopped

early for futility,with similar2-year stroke rates in both

groups.1Medical management included a goal BP of

#130/85mm Hg.In this issue of Neurology,1the91

individuals in the nonsurgical arm of COSS with

follow-up BP measurements were evaluated based on

their actual attained BP.Stroke rates were higher

among those individuals who did not reach the target

BP than among those with a BP at target(#130/85

mm Hg);no other differences were noted between the

groups.Stroke risk was consistently low at lower BPs,

without a J-shaped increase at the lowest pressures,as

has been observed in some other studies.2

Patients in COSS are at high risk for stroke;these

data suggest that findings from observational studies

and clinical trials might be uniformly applied to patients

at risk,regardless of mechanism of https://www.360docs.net/doc/9616244951.html,e of antihy-

pertensive medications for secondary stroke prevention is

consistently associated with lower recurrent stroke rates,

both in clinical trials3and observational studies,4and

even in the acute setting in patients with intracere-

bral hemorrhage.5An increase in stroke risk may

occur at especially low pressures,2although this is

not observed in all studies;whether or not low

pressures are dangerous in some people remains

unknown.The Systolic Blood Pressure Intervention

Trial,currently under way,randomizes patients to

systolic BP of,140mm Hg vs,120mm Hg and

will help address this uncertainty.

Despite multiple clinical trials supporting lower

stroke rates associated with reduction in BP,the Amer-

ican Stroke Association guidelines for secondary stroke

prevention suggest that an“absolute target BP level and

reduction are uncertain and should be individualized.”6

Prior studies of perfusion in individuals with carotid

artery disease suggest that individualizing BP goals

might be needed—individuals with carotid disease

and impaired perfusion may have more stroke at lower

BPs.7Others have recommended that“in patients with

symptomatic carotid occlusion,treatment of hyperten-

sion should not be too aggressive.”8Reanalysis of data

from the carotid surgery trials found no further increase

in stroke risk with lower BPs and a unilateral carotid

occlusion,although there was an increased risk at lower

pressures in individuals with bilateral carotid stenosis.9

The findings in this issue of Neurology,however,sug-

gest that even patients with carotid occlusion might still

require reduction of BP,to a level similar to what is

recommended in a broader population.10Patients with

carotid occlusion are at particularly high risk for stroke,

especially when increased oxygen extraction fraction is

also found.11Therefore,if this population is seen as an

especially high-risk population,and not a unique pop-

ulation in whom standard best clinical practice should

not be applied,tighter BP control makes sense,at least

beyond the acute to subacute time period after symp-

tomatic presentation.

These findings are observational in nature and thus

might be susceptible to biases due to the baseline char-

acteristics of the2BP groups.Individuals who success-

fully maintained BPs below130/85mm Hg are likely to

differ in critical ways from individuals with higher pres-

sures.More antihypertensives were required for those in-

dividuals with higher BPs,suggesting more resistant

hypertension,higher BP at baseline,or lesser adherence

to medications.Any of these factors could indepen-

dently contribute to increased stroke risk,although the

hazard ratio for benefit,that is,for reduction in

stroke during follow-up,was the same among patients

who received antihypertensive treatment at every visit

From the Department of Neurology(R.F.G.),Johns Hopkins University School of Medicine,Baltimore,MD;and The George Institute for Global Health(J.C.),Sydney,Australia.

Go to https://www.360docs.net/doc/9616244951.html, for full disclosures.Funding information and disclosures deemed relevant by the authors,if any,are provided at the end of the editorial.

1018?2014American Academy of Neurology

(3.7,p,0.06)as it was in the group as a whole(also

3.7,p,0.02),suggesting that the benefit was not just

a manifestation of increased baseline risk.Observed BP level could also reflect differences in collateral circula-tion or extent of hemodynamic compromise,and level of BP could just be a surrogate marker for risk of stroke. Yet it should be noted that high BP is usually a man-ifestation of increased vasoconstriction and peripheral resistance,leading to impaired tissue perfusion and greater tendency to ischemia,while a lower pressure suggests relaxation of vascular smooth muscle with improved perfusion.This could have contributed to the reduction in stroke during follow-up.

Although patients with carotid occlusion are likely to differ in some ways from other stroke and TIA patients,the results from this analysis,com-bined with the recently published Secondary Pre-vention of Small Subcortical Strokes data12and other large clinical trials,which suggest lower stroke rates in individuals with systolic BP,130mm Hg, support lower BP goals in the secondary prevention of stroke,regardless of the mechanism.Given that COSS is a purely observational study,the findings reported in this issue can only be regarded as hypothesis generating.The questions surrounding the optimal management of BP in patients with cerebral ischemia or with ischemic stroke can only be resolved by rigorous,well-conducted randomized clinical trials.

STUDY FUNDING

No targeted funding reported.

DISCLOSURE

The authors report no disclosures relevant to the manuscript.Go to https://www.360docs.net/doc/9616244951.html, for full disclosures.REFERENCES

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