Cerebral blood flow velocity and vasomotor reactivity during autonomic challenges in heart failure.

Background: Significant alterations in autonomic nervous system (ANS) function, vasomotor reactivity, and cerebral blood flow may develop from damage to brain ANS regulatory areas in heart failure (HF). This preferentially right-sided injury occurs largely in autonomic structures perfused by the middle cerebral artery. Indications of altered, asymmetrical perfusion raise the potential for further neural damage.

Objective: To determine whether the extent of middle cerebral artery blood flow velocity and vasomotor reactivity is altered on one side of the brain over the other in HF versus control subjects, three ANS challenges were administered-each challenge recruited ANS regulatory areas potentially injured in HF.

Methods: Transcranial Doppler ultrasonography was used to measure cerebral blood flow velocity and vasomotor reactivity in 40 HF (mean age = 52.7 years, SD = 7.5; 27 men; left ventricular ejection fraction = 26.8, SD = 8.3) and 42 control subjects (mean age = 48.3 years, SD = 6.0; 22 men) during 5% CO2 and hyperventilation, Valsalva, and orthostatic (upper body tilt) challenges.

Results: Lower cerebral blood flow velocity and abnormal vasomotor reactivity (p < .01) were noted in HF middle cerebral arteries during all challenges. More right-sided flow velocity reductions appeared in HF, with laterality differences noted during CO2 and orthostatic (p < .05), but not Valsalva challenges.

Discussion: Diminished cerebral blood flow velocity and altered vasomotor reactivity were associated with HF, changes being preferentially on the right side; the asymmetry was more pronounced during CO2 and orthostatic challenges. The impaired blood flow regulation may contribute to the lateralized brain pathology in ANS areas, undermining autonomic control in HF.