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Systolic blood pressure that is too low -- as well as too high -- may put patients who have had a noncardioembolic ischemic stroke at risk for another one, researchers found.

Compared with patients who maintained a systolic pressure in the 130s, those with average readings below 120, or of 140 and higher, had an elevated risk of recurrent stroke (HRs 1.23 to 2.08), according to Bruce Ovbiagele, MD, of the University of California San Diego, and colleagues.

Also, those same groups, in addition to patients with a systolic pressure of 120 to less than 130, had a greater risk of a composite of stroke, MI, or death from vascular causes (HRs 1.16 to 1.94), the researchers reported in the Nov. 16 issue of the Journal of the American Medical Association.

"Our results indicate that there may indeed be thresholds of benefit or harm with regard to short-term to longer-term systolic blood pressure levels after a recent noncardioembolic ischemic stroke, and imply that clinicians regularly caring for stroke patients in the outpatient setting may need to be vigilant about how low a given patient's blood pressure is within the normal range to promote favorable outcomes," they wrote.

Guidelines from the American Heart Association/American Stroke Association indicate that the risk of recurrent stroke continues to decrease as the systolic blood pressure drops, with a reading of less than 120 mm Hg considered normal.

There are no data, however, regarding the association of maintaining various systolic blood pressure levels within the normal range and the risk of vascular events after a recent ischemic stroke.

To explore the issue, Ovbiagele and colleagues conducted a post-hoc analysis of the Prevention Regimen for Effectively Avoiding Second Strokes (PRoFESS) trial, which involved 20,330 patients (mean age 66.1) who had had a recent noncardioembolic ischemic stroke.

The trial compared aspirin and extended-release dipyridamole with clopidogrel and also telmisartan (Micardis) with placebo for the prevention of recurrent stroke. None of the treatments carried a significant advantage through an average of 2.5 years of follow-up.

So in the post-hoc analysis, the researchers grouped all of the patients together and divided them according to their average systolic blood pressure during the study -- very low-normal was less than 120, low-normal was 120 to less than 130, high-normal was 130 to less than 140, high was 140 to less than 150, and very high was 150 and higher.

Recurrent stroke rates were 8%, 7.2%, 6.8%, 8.7%, and 14.1%, respectively, across the groups.

Compared with patients in the high-normal group, those at both ends of the systolic blood pressure spectrum had a greater risk of recurrent stroke.

The researchers noted that the relationship between very low-normal systolic blood pressure and recurrent stroke "could simply represent a marker of known or unknown poor global health, keying healthcare practitioners to facilitate optimal management of the patient's known chronic severe conditions or to consider further inquiry into potentially undiagnosed major medical problems."

But many of these major conditions were accounted for in the analysis, suggesting that very low-normal readings may not have been an indication of an underlying severe condition at baseline, they wrote.

"These data are hypothesis generating, and the notion that aggressively and consistently lowering blood pressure levels within the normal range in the short term to longer term after an index ischemic stroke is not beneficial remains unproven, and will require the conduct of dedicated clinical trials comparing intensive with usual blood pressure reduction in the stable follow-up period after a stroke."

Ovbiagele and colleagues suggested that clinicians may want to shoot for higher blood pressure targets than those in the guidelines.

"The results of this analysis support aiming for consistent systolic blood pressure levels of less than 140 mm Hg and less than 90 mm Hg for diastolic blood pressure among recent ischemic stroke patients, particularly within the first six months," they wrote.

They acknowledged that the study was limited by the post-hoc design, the potential for unmeasured confounding, and the unknown applicability to patients with cardioembolic stroke.

From the American Heart Association:

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