From the Guidelines
Low blood pressure that can cause an ischemic stroke typically occurs when systolic blood pressure falls below 100 mmHg or diastolic pressure drops below 70 mmHg, as noted in a study by Castillo et al, cited in the guidelines from the American Heart Association/American Stroke Association 1. This hypotension reduces cerebral perfusion pressure below the threshold needed to maintain adequate blood flow to brain tissue. When blood pressure drops too low, areas of the brain that are already compromised by atherosclerosis or other vascular conditions may not receive sufficient oxygen and nutrients, leading to ischemic damage. The risk is particularly high in patients with significant carotid artery stenosis or intracranial arterial disease, as these conditions already limit blood flow to certain brain regions. Some key points to consider include:
- The cause of hypotension should be sought, with potential causes including aortic dissection, volume depletion, blood loss, and decreased cardiac output secondary to myocardial ischemia or cardiac arrhythmias 1.
- Correction of hypovolemia and optimization of cardiac output are important priorities during the first hours after stroke, with treatment including volume replacement with normal saline and correction of cardiac arrhythmias 1.
- If these measures are ineffective, vasopressor agents such as dopamine may be used, as noted in the guidelines from the American Heart Association/American Stroke Association 1.
- A more recent study published in 2013 also highlights the importance of individualizing the definition of arterial hypotension, considering a blood pressure that is lower during acute ischemic stroke than the premorbid pressure as potentially harmful 1. Elderly patients and those with diabetes or hypertension are especially vulnerable to hypotension-induced strokes. If you experience symptoms of low blood pressure along with any neurological symptoms like weakness, numbness, vision changes, or speech difficulties, seek emergency medical attention immediately as prompt treatment is essential to minimize brain damage.
From the Research
Low Blood Pressure Level and Ischemic Stroke
- The relationship between low blood pressure and ischemic stroke is complex, and research has yielded mixed results 2.
- A study published in 2021 found that a diastolic blood pressure of less than 60 mmHg was associated with an increased risk of cardiovascular events, including nonfatal stroke, in patients with high cardiovascular risk and a treated systolic blood pressure of less than 130 mmHg 2.
- The same study found that a diastolic blood pressure between 70 and 80 mmHg was associated with the lowest risk of cardiovascular events, including nonfatal stroke 2.
- Another study published in 2019 found that dual antiplatelet therapy with clopidogrel and aspirin was associated with a lower risk of recurrent stroke, but also an increased risk of bleeding, compared to monotherapy 3.
- The optimal blood pressure target for patients with a history of ischemic stroke or transient ischemic attack is not well established, and further research is needed to determine the best approach for managing blood pressure in these patients 4, 5, 6.
Key Findings
- A diastolic blood pressure of less than 60 mmHg is associated with an increased risk of cardiovascular events, including nonfatal stroke 2.
- A diastolic blood pressure between 70 and 80 mmHg is associated with the lowest risk of cardiovascular events, including nonfatal stroke 2.
- Dual antiplatelet therapy with clopidogrel and aspirin may be effective for secondary stroke prevention, but is also associated with an increased risk of bleeding 3.