Hemodynamic Factors and Symptomatic Carotid Artery Occlusion

To the Editor: Dr Grubb and colleagues¹ used positron emission tomography to demonstrate the influence of cerebral hemodynamic changes resulting from internal carotid arteryocclusion on the subsequent occurrence of ischemic strokes. Presumably, the reduction of cerebral blood flow due to a reduced perfusion pressure is one of the most important determinants of the hemodynamic changes. A recent study using ambulatory blood pressure monitoring has shown that variations in the diurnal rhythm of blood pressure may also influence cerebral ischemic events. Both nondipping (a diminished nocturnal blood pressure fall) and extreme dipping (an exaggerated fall) appear to be risk factors for silent cerebral infarction as assessed by brain magnetic resonance imaging in elderly persons with hypertension, when compared with the normal dipping pattern of nocturnal blood pressure decrease.² Thus, in extreme dippers who also have carotid artery occlusion, aggressive antihypertensive treatment based on an elevated clinic daytime blood pressure might be expected to trigger ischemic cerebrovascular episodes during the night. Since more than half of the patients described in the study by Grubb et al¹ were hypertensive, information about the status of their antihypertensive treatment and the time of onset of their strokes would be helpful for deciding the best medical treatment of patients with carotid artery occlusion.