Relationship between blood pressure and stroke risk in patients with symptomatic carotid occlusive disease
P M Rothwell1, S C Howard, J D Spence
1Stroke Prevention Research Unit, Department of Clinical Neurology, Radcliffe Infirmary, Woodstock Rd, Oxford OX2 6HE UK. peter.rothwell@clneuro.ox.ac.uk
Insights
Blood pressure lowering reduces stroke risk, but aggressive reduction may be harmful for patients with severe bilateral carotid stenosis. This specific group has an inverted blood pressure-stroke risk relationship.
Area of Science:
- Neurology
- Cardiovascular Medicine
- Clinical Trials
Background:
- Blood pressure management is crucial for preventing recurrent stroke and cardiovascular events after TIA or stroke.
- Severe carotid occlusive disease, including carotid occlusion or bilateral stenosis, presents unique challenges due to potential cerebral hypoperfusion.
- Systemic blood pressure may directly influence cerebral perfusion in patients with critical carotid stenosis.
Purpose of the Study:
- To investigate the effect of carotid artery disease on the relationship between blood pressure and stroke risk in patients with recent TIA or stroke.
- To determine if severe carotid stenosis modifies the blood pressure-stroke risk association.
- To assess risks and benefits of blood pressure lowering in patients with severe carotid occlusive disease.
Main Methods:
- Compared blood pressure-stroke risk relationships in TIA/stroke patients with significant carotid stenosis (ECST, NASCET) versus those with low carotid disease prevalence (UK-TIA).
- Analyzed blood pressure-stroke risk in subgroups with unilateral carotid occlusion and bilateral >=70% stenosis within ECST and NASCET trials.
- Examined interactions between blood pressure parameters (systolic, diastolic, pulse pressure) and stroke risk based on carotid disease severity.
Main Results:
- Stroke risk increased with blood pressure in most patients, but less steeply in those with carotid stenosis compared to the general TIA/stroke population.
- Unilateral carotid occlusion did not alter the blood pressure-stroke risk relationship.
- Bilateral >=70% carotid stenosis significantly inverted the blood pressure-stroke risk relationship, with higher risks at lower blood pressures.
Conclusions:
- While elevated blood pressure generally increases stroke risk in symptomatic carotid artery disease, the relationship is attenuated.
- Aggressive blood pressure lowering may be contraindicated in patients with bilateral >=70% carotid stenosis due to an inverted risk profile.
- This subgroup, though small, faces a high risk of recurrent stroke and requires careful management consideration.
Background And Purpose:
Blood pressure lowering in patients with a previous transient ischemic attack (TIA) or stroke reduces the risk of recurrent stroke and coronary vascular events. However, there is uncertainty about the risks and benefits in patients with severe carotid occlusive disease, particularly those with a carotid occlusion or bilateral > or =70% carotid stenosis in whom cerebral perfusion is often impaired and may depend directly on systemic blood pressure. Therefore, we studied the effect of carotid artery disease on the relationship between blood pressure and stroke risk in patients with recent TIA or stroke.
Methods:
We compared the relationship between blood pressure (systolic and diastolic blood pressures, pulse pressure) and stroke risk in TIA and stroke patients with documented stenosis of at least 1 carotid artery [European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET)] with that in TIA and stroke patients with a low prevalence of carotid disease [United Kingdom Transient Ischaemic Attack (UK-TIA) Aspirin Trial]. In ECST and NASCET, we also determined the relationship between blood pressure and stroke risk in patients with unilateral carotid occlusion and patients with bilateral > or =70% carotid stenosis.
Results:
Stroke risk on medical treatment increased with blood pressure in ECST and NASCET, but the relationships were less steep than in the UK-TIA trial. The relationship between blood pressure and stroke risk was not affected by the presence of a unilateral carotid occlusion but was significantly affected by the presence of bilateral carotid stenosis > or =70% (interaction: systolic blood pressure, P=0.002; diastolic blood pressure, P=0.03; pulse pressure, P=0.003). In this group, the relationship was inverted because of the high stroke risks at lower blood pressures. This interaction was not present after carotid endarterectomy and was not present for the risk of myocardial infarction.
Conclusions:
The risk of stroke increases with blood pressure in the great majority of patients with symptomatic carotid artery disease, but the relationship is less steep than in other patients with TIA or stroke. The relationship is unaffected by unilateral carotid occlusion alone but is inverted in patients with bilateral > or =70% carotid stenosis, suggesting that aggressive blood pressure lowering may not be advisable in this group. These patients represent only a few percent of all patients with TIA or stroke but have a high risk of recurrent stroke.
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