Cerebral Flow Velocities During Daily Activities Depend on Blood Pressure in Patients With Chronic Ischemic Infarctions

Abstract

Background and Purpose-Target blood pressure (BP) values for optimal cerebral perfusion after an ischemic stroke are still debated. We sought to examine the relationship between BP and cerebral blood flow velocities (BFVs) during daily activities. Methods-We studied 43 patients with chronic large vessel ischemic infarctions in the middle cerebral artery territory (aged 64.2Ϯ8.94 years; at 6.1Ϯ4.9 years after stroke) and 67 age-matched control subjects. BFVs in middle cerebral arteries were measured during supine baseline, sitting, standing, and tilt. A regression analysis and a dynamic phase analysis were used to quantify the BP-BFV relationship. Results-The mean arterial pressure was similar between the groups (89Ϯ15 mm Hg). Baseline BFVs were lower by approximately 30% in the patients with stroke compared with the control subjects (Pϭ0.0001). BFV declined further with postural changes and remained lower in the stroke group during sitting (Pϭ0.003), standing (Pϭ0.003), and tilt (Pϭ0.002) as compared with the control group. Average BFVs on the stroke side were positively correlated with BP during baseline (Rϭ0.54, Pϭ0.0022, the slope 0.46 cm/s/mm Hg) and tilt (Rϭ0.52, Pϭ0.0028, the slope 0.40 cm/s/mm Hg). Regression analysis suggested that BFV may increase approximately 30% to 50% at mean BP Ͼ100 mm Hg. Orthostatic hypotension during the first minute of tilt or standing was independently associated with lower BFV on the stroke side (Pϭ0.0008). Baseline BP-BFV phase shift derived from the phase analysis was smaller on the stroke side (Pϭ0.0006). Conclusion-We found that BFVs are lower in patients with stroke and daily activities such as standing could induce hypoperfusion. BFVs increase with mean arterial pressure Ͼ100 mm Hg. Dependency of BFV on arterial pressure may have implications for BP management after stroke. Further prospective investigations are needed to determine the impact of these findings on functional recovery and strategies to improve perfusion pressure during daily activities after ischemic stroke. (Stroke. 2010;41:61-66.)

Postural Changes in Blood Pressure and Incidence of Ischemic Stroke Subtypes

“…Another possible mechanism is a systemic BP drop directly leading to the occurrence of nonlacunar thrombotic and cardioembolic stroke. Cerebral blood flow and systemic BP are positively associated, 26 and its autoregulation is impaired in patients who have orthostatic tachycardia during an orthostatic challenge. 27 Moreover, postural change has been identified as the most important trigger of ischemic stroke out of seven predefined emotional, behavioral or environmental stimuli.…”

The relationship between blood pressure and cognitive function

“…18 Therefore, in the setting of hypotension syndromes, the upright-position BP might be below the range of effective regulation, leading to perfusion decline. In these patients, daily living activities can induce hypoperfusion 25 and lead to syncope, 26 falls, or ischemia and cognitive changes. 27 …”

Update on the Management of Hypertension for Secondary Stroke Prevention

“…In these patients, the velocities of basal cerebral blood flow were 30% lower than in subjects without prior stroke, and cerebral flow velocities were more dependent on BP values [14]. …”