Increased blood pressure variability during the subacute stage of ischemic stroke is associated with worsened functional outcomes at 3 months

Image: PD

Key study points:

1. There is a high prevalence of hypertension among patients during the subacute stage of stroke.

2. Presence of a large difference between maximum and minimum recorded blood pressures during the subacute stage of ischemic stroke was the most significant predictor of poor functional outcome.

Primer: Blood pressure (BP) management has long been a topic of interest when discussing prevention and management of ischemic stroke. Numerous publications have suggested that lowering BP can reduce risk of primary stroke as well as delay or prevent recurrence in those who have already suffered a stroke. Indeed, research has shown that treatment with antihypertensive agents reduce risk of stroke, non-fatal stroke, myocardial infarction, and total vascular events among those who had previously suffered an ischemic or hemorrhagic stroke or transient ischemic attack. Moreover, several studies suggest that BP may be an important prognostic factor in patients actively suffering an ischemic stroke. High BP during acute ischemic stroke and primary intracranial hemorrhage has been associated with subsequent death, dependency, or deterioration. Thus, by theoretically reducing brain edema, decreasing the risk of hemorrhagic conversion, and preventing recurrent ischemic stroke, lowering BP during the acute stage has been thought to be beneficial.

However, several recent studies suggest aggressive reductions in BP may actually worsen outcomes, likely due to reduce perfusion in already ischemic brain regions. As a result, treatment of hypertension during acute ischemic stroke remains a controversial issue and the AHA/ASA guidelines now recommend withholding antihypertensive agents unless the patient is extremely hypertensive (systolic BP > 220 mmHg or diastolic BP > 120 mmHg)

However, there is a paucity of research regarding the role of BP during the subacute stage – the time after patients have been stabilized but before they have recovered sufficiently for discharge. The authors of this study sought to investigate the role of BP during this subacute stage in determining short-term functional outcomes among patients suffering ischemic strokes.

Background reading:

1. Blood Pressure Reduction and Secondary Prevention of Stroke and Other Vascular Events [Stroke]

2. High Blood Pressure in Acute Stroke and Subsequent Outcome [Hypertension]

3. Guidelines for the Early Management of Adults With Ischemic Stroke [Stroke]

This [retrospective, observational] study: Data on 2,271 consecutive patients hospitalized for a stroke at the Seoul National University Bundang Hospital between 2004 and 2009 were obtained. Several BP parameters were noted for each individual. Patients were then surveyed at 3 months after stroke onset to assess function on the modified Rankin scale (mRS). Function was adjusted for the severity of the stroke (baseline National Institutes of Health Stroke Scale (NIHSS) score). The authors found that 46.5% of patients had a mean systolic BP (SBP) ≥ 140 mmHg and 9.4% had a mean diastolic BP (DBP) ≥ 90 mmHg. However, the average BP was lower by 1.5 (CI: 0.94-1.98) mmHg in subacute stage compared to acute stage of ischemic stroke. Further, BP variables indicating BP variability (including difference between maximum and minimum values, standard deviation (SD), and coefficient of variation (CV) of SBP and maximum, difference between maximum and minimum values, SD, and CV of DBP) were independently associated with worse functional outcomes. Conversely, mean SBP and DPB were not associated with poor short term function after ischemic stroke.

In sum: This study was one of the first to investigate the role of BP in the subacute stage of ischemic stroke and provides the strongest evidence to date supporting two key findings: 1) BP remained elevated in the subacute stage despite medical and neurological stabilization of the patient and 2) Variability in BP, but not mean BP, was associated with worsened 3-month functional outcomes in patients suffering an ischemic stroke. The authors speculate that variation in BP may put patients at risk for stroke recurrence, end organ damage, and cerebral hypoperfusion. Thus, BP variability may provide an important prognostic factor for future function in stroke patients and the reduction of this variability may be a crucial clinical goal.

Several important limitations to the study are present. First, as the study design was retrospective and based on data gathered in a single center, there may be limits to its generalizability. Second, no data was gathered on the use of hypertensive agents. Given the effect of these medications on brain perfusion, their preferential use in certain patients may have affected functional outcomes. Finally, it may be possible that BP variability is caused by stroke severity and thus the results linking BP variations to functional outcomes may be confounded.

Click to read the study in [Neurology]

By [MK]

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