Hemodynamic effect of external counterpulsation is a different measure of impaired cerebral autoregulation from vasoreactivity to breath-holding.

BACKGROUND AND
PURPOSE: External counterpulsation (ECP) is a novel method to increase cerebral blood flow, which may benefit acute ischaemic stroke patients. Our aim was to identify whether the hemodynamic effect of ECP is associated with cerebral vasoreactivity to breath-holding.
METHODS: Thirty-seven recent ischaemic stroke patients with large artery steno-occlusive disease were recruited together with 20 healthy controls. All underwent ECP treatment and a breath-holding test combined with transcranial Doppler monitoring on bilateral middle cerebral arteries was performed. The data of the stroke patients were designated as ipsilateral or contralateral based on the side of the infarct, whilst the average of both sides was used in controls. The cerebral augmentation index (CAI) was used to evaluate the augmentation effects of ECP. Cerebral vasoreactivity was assessed by using the breath-holding index (BHI).
RESULTS: Middle cerebral artery mean flow velocities significantly increased in the stroke group after ECP but not in controls. BHIs were much smaller in the stroke group than in the controls. The CAI did not correlate with the BHI in either the ipsilateral or contralateral side of the stroke group or in controls. For stroke patients, BHI was significantly lower on the ipsilateral side than the contralateral side, but the CAI showed no difference between the two cerebral hemisphere sides. The CAI of stroke patients was significantly related to mean blood pressure change on the ipsilateral side.
CONCLUSION: The dynamic augmentation effects of ECP as measured by the CAI were different from the well established vasoreactivity to breath-holding. The CAI is suggested as a measure of how well the brain accommodates blood flow augmentation during ECP.