Assessing dynamic cerebral autoregulation after stroke using a novel technique of combining transcranial Doppler ultrasonography and rhythmic handgrip.

OBJECTIVES: Dynamic cerebral autoregulation (CA) is impaired after stroke. Methods employed to assess this phenomenon usually involve deliberate alterations in blood pressure (BP) by physical means. We performed a pilot study to assess dynamic CA in acute stroke patients using a novel technique of combining transcranial Doppler (TCD) ultrasonography with rhythmic handgrip.
METHODS: Ten patients with ischaemic stroke in the middle cerebral artery (MCA) territory were studied. We performed continuous recordings of bilateral MCA velocities and used rhythmic handgrip to induce BP oscillations. Changes in autoregulation were indicated by changes in phase shift and gain of MCA velocity in relation to BP. Patients were examined at <7 days, 6 weeks, and 3 months after stroke.
RESULTS: There were no significant differences in phase shift or gain between the affected and unaffected cerebral hemispheres. Combining the results from both hemispheres, there was a trend of increasing phase shift (P=0.04) and decreasing gain (P=0.24) over the first three months after stroke, indicating improving CA. Rhythmic handgrip produced an average percentage change in BP (peak-to-trough) of 10% around the mean, and the frequency of the induced BP oscillations was very similar to that of the rhythmic handgrip.
CONCLUSIONS: Combining TCD with rhythmic handgrip appeared to be a useful technique for assessing dynamic CA and it deserves further studies. In this pilot study, there was some evidence that CA might improve up to 3 months after ischaemic stroke.