Background and purpose: External counterpulsation improves cerebral perfusion velocity in acute stroke and may stimulate collateral artery growth. However, whether (non-acute) at-risk patients with high-grade carotid artery disease may benefit from counterpulsation needs to be validated.

Methods: Twenty-eight patients (71 ± 6.5 years, five women) with asymptomatic unilateral chronic severe internal carotid artery stenosis (>70%) or occlusion were randomized to receive 20 min active counterpulsation followed by sham treatment or vice versa. Cerebral blood flow velocity (CBFV) (measured bilaterally by transcranial middle cerebral artery Doppler), tissue oxygenation index (TOI) (measured over the bilateral prefrontal cortex by near-infrared spectroscopy) and cerebral hemodynamic parameters, such as relative pulse slope index (RPSI), were monitored.

Results: Ipsilateral mean CBFV (ΔV_mean +3.5 ± 1.2 cm/s) and tissue oxygenation (ΔTOI +2.86 ± 0.8) increased significantly during active counterpulsation compared to baseline, whilst the sham had little effect (ΔV_mean +1.13 ± 1.1 cm/s; ΔTOI +1.25 ± 0.65). On contralateral sides, neither counterpulsation nor sham control had any effect on either parameter. During counterpulsation, early dynamic changes in ΔRPSI of the ipsilateral CBFV signal predicted improved tissue oxygenation during counterpulsation (odds ratio 1.179, 95% confidence interval 1.01-1.51), whilst baseline cerebrovascular reactivity to hypercapnia failed to show an association.

Conclusions: In patients with high-grade carotid disease, ipsilateral cerebral oxygenation and blood flow velocity are increased by counterpulsation. This is a necessary condition for the stimulation of regenerative collateral artery growth and thus a therapeutic concept for the prevention of cerebral ischaemia. This study provides a rationale for further clinical investigations on the long-term effects of counterpulsation on cerebral hemodynamics and collateral growth.