Hypertension in Acute Ischemic Stroke: A Compensatory Mechanism or an Additional Damaging Factor?

Abstract and Introduction

Hypertension is the most important modifiable risk factor for ischemic stroke, and antihypertensive treatment is of paramount importance to reduce the incidence of stroke mortality and morbidity. However, the significance and best management of hypertension observed during the first hours after stroke onset are still a matter of debate. Recent guidelines recommend clinical trials to ascertain whether antihypertensive therapy in the acute phase of stroke is beneficial.This review summarizes previous reports on blood pressure management during the first 72 hours after an acute ischemic stroke and shows that a large number of papers published in the past 20 years failed to convince that early use of antihypertensives in unselected patients with acute ischemic stroke is beneficial.The authors stress that only blood pressure values repeatedly higher than 220/120 mm Hg should be gradually lowered and kept in the range of 180-220 mm Hg systolic and 100-120 mm Hg diastolic.The usefulness of increasing blood pressure with vasopressive agents in selected patients may deserve adequate testing with randomized clinical trials.

Stroke is the third leading cause of death in Western populations after coronary heart disease and cancer. Furthermore, stroke is the most common life-threatening neurological disorder, and the resulting disability is the most important single cause of inability among these populations.

High blood pressure is the most prevalent modifiable risk factor for stroke.^[1] Large-scale observational studies have shown that blood pressure is positively and continuously associated with the risk of stroke in a log-linear fashion. Elevated blood pressure is positively related to both ischemic and hemorrhagic stroke, but the association is steeper for hemorrhagic stroke. A similar association exists for blood pressure and the risk of recurrent stroke.

Blood pressure lowering is an effective measure to reduce the burden of stroke. According to many clinical trials, blood pressure lowering in various high-risk groups reduces the risk of stroke by more than one third. Not only do hypertensive patients benefit from blood pressure lowering, but high-risk patients with normal blood pressure also benefit.^[1] Trials have shown that diuretics, ß blockers, angiotensin-converting enzyme inhibitors, calcium antagonists, and angiotensin-II-receptor blockers are effective in reducing the risk of stroke.^[1]

Hypertension is common in patients admitted for an acute ischemic stroke, and a transient blood pressure rise can be found also in previously normotensive patients, whereas in patients with hemorrhagic stroke hypertension in the acute phase is more severe than the usual blood pressure elevation.^[2] It is probably linked to lesions of particular cerebral areas causing impaired neurogenic cardiovascular control, dysautonomic regulation, and a reflex response to cerebral ischemia^[3] or secondary to baroreflex failure.^[4] Other mechanisms of stroke "related" to hypertension include mental stress^[5] and increased sympathetic drive.^[6]

The appropriate management of raised blood pressure at stroke onset remains an unsolved question. In fact, blood pressure may decline spontaneously and unpredictably without intervening medications.^[7] Furthermore, the incorrect use of antihypertensive drugs in acute stroke may reduce the pressure-dependent cerebral perfusion to the ischemic penumbra, the area surrounding the ischemic necrotic core perfused by collaterals at low flow, and therefore may worsen cerebral damage.^[8] Conversely, poststroke hypertension could be deleterious and facilitate edema and hemorrhagic transformation in the ischemic tissue.^[9]

For these reasons, it is not surprising that previous studies gave variable results regarding the prognostic value of high blood pressure in acute stroke.^[10,11,12] It also has to be noted that many studies were uncontrolled and did not distinguish between ischemic and hemorrhagic strokes. Finally, little is known about the relationships between type and site of acute stroke, rise of blood pressure, and neurologic outcome. Not unexpectedly, even the most recent guidelines on blood pressure management in acute stroke provided circumstantial suggestions based not on clinical trials but on pathophysiological reasoning and recommended ad hoc clinical trials.^[13] However, are clinical trials on antihypertensive treatment in acute stroke really needed, or is the clinical evidence collected so far enough for clinical decision making in acute ischemic stroke?

To answer this question, we summarized the reports published during the past 20 years on the relationships between blood pressure during the first hours after acute ischemic stroke and outcome and on the effects of deliberately changing blood pressure in patients with acute stroke. To this end, PubMed^[14] was searched for "acute ischemic stroke" and "blood pressure." Then, the Cochrane review^[15] was compared with the search results and the searched literature collected so far and cross-checked for consistency.

Cardiovasc Rev Rep. 2004;25(2) © 2004 Le Jacq Communications, Inc.

Cite this: Hypertension in Acute Ischemic Stroke: A Compensatory Mechanism or an Additional Damaging Factor? - Medscape - Mar 01, 2004.