J-shaped curve found for SBP and recurrent stroke
MedWire News: Patients with recent stroke may not tolerate low-normal systolic blood pressure (SBP) levels, indicate results from PRoFESS.
There is a J-shaped relationship between SBP and recurrent events in patients with cardiovascular disease, but the relationship between SBP and recurrence in patients with stroke is thought to be linear. The current findings, published in JAMA, dispute this notion.
"Our results indicate that there may indeed be thresholds of benefit or harm with regard to short-term to longer-term SBP 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 BP is within the normal range to promote favorable outcomes," say the researchers.
Bruce Ovbiagele (University of California, San Diego, USA) and colleagues studied SBP and outcomes among 20,330 patients, aged at least 50 years, who participated in the PRoFESS (Prevention Regimen for Effectively Avoiding Second Strokes) trial. The patients had noncardioembolic ischemic stroke no more than 120 days before recruitment; the median was 15 days.
Over an average 2.5 years of follow-up, stroke rates were 8.7% and 14.1% among patients with high SBP (140 to <150 mmHg) and very high SBP (≥150 mmHg), respectively.
Among those with SBP in the normal range, stroke rates were 8.0% when SBP was very low-normal (<120 mmHg), 7.2% when it was low-normal (120 to <130 mmHg), and 6.8% when it was high-normal (130 to <140 mmHg).
After accounting for confounders, the risk for stroke was increased a significant 1.23-fold among patients with high SBP, relative to those with high-normal SBP, and a significant 2.08-fold in the very high SBP group.
However, stroke risk was also significantly elevated among patients with very low-normal SBP, at a 1.29-fold increase.
Rates of a composite outcome of stroke, myocardial infarction, and vascular death were significantly elevated among patients in all SBP categories compared with those in the high-normal group.
The researchers note that their findings are at odds with research in patients at high vascular risk, which suggested that low SBP protects against stroke. They say: "It is conceivable patients free of known stroke may tolerate low-normal BP levels better than those with a recent bout of symptomatic cerebral ischemia with brain parenchymal damage."
They team also suggests that the J-shaped curve may only apply relatively soon after stroke, when patients are conceivably at their most vulnerable, explaining why studies that recruited patients later after the initial stroke found a linear relationship between SBP and stroke risk.
"These data are hypothesis generating and the notion that aggressively and consistently lowering BP 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 BP reduction in the stable follow-up period after a stroke," conclude the researchers.
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By Eleanor McDermid