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 64.2±8.94 years; at 6.1±4.9 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 (89±15 mm Hg). Baseline BFVs were lower by approximately 30% in the patients with stroke compared with the control subjects ( P =0.0001). BFV declined further with postural changes and remained lower in the stroke group during sitting ( P =0.003), standing ( P =0.003), and tilt ( P =0.002) as compared with the control group. Average BFVs on the stroke side were positively correlated with BP during baseline ( R =0.54, P =0.0022, the slope 0.46 cm/s/mm Hg) and tilt ( R =0.52, P =0.0028, the slope 0.40 cm/s/mm Hg). Regression analysis suggested that BFV may increase approximately 30% to 50% at mean BP >100 mm Hg. Orthostatic hypotension during the first minute of tilt or standing was independently associated with lower BFV on the stroke side ( P =0.0008). Baseline BP–BFV phase shift derived from the phase analysis was smaller on the stroke side ( P =0.0006). 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 >100 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.