Effect of cardiac resynchronization therapy on cerebral blood flow

Decreased cerebral blood flow is frequently observed in patients with heart failure, and this could be the result of impaired cardiac systolic function. Cardiac resynchronization therapy (CRT) improves cardiac function and heart failure symptoms in selected patients. The effects of CRT on cerebral blood flow have not been previously evaluated. In the present study, left ventricular systolic function and cerebral blood flow were assessed in 35 patients with heart failure, before and 6 months after CRT. Additionally, 15 patients with heart failure, who were not candidates for CRT, were included as a control group. The peak systolic velocity, end-diastolic velocity, mean velocity, and pulsatility index ([peak systolic velocity--end-diastolic velocity]/mean velocity) were obtained using transcranial Doppler from the right middle cerebral artery from the temporal window in all subjects. Response to CRT was defined as a reduction in the left ventricular end-systolic volume of > or =15%. At 6 months of follow-up, the peak systolic velocity had significantly increased from 83 +/- 20 cm/s to 100 +/- 20 cm/s (p = 0.001), the end-diastolic velocity had increased from 29 +/- 7 cm/s to 37 +/- 8 cm/s (p <0.001), and the mean velocity had increased from 47 +/- 10 cm/s to 58 +/- 11 cm/s (p <0.001) only in the responders to CRT. In contrast, no significant changes in cerebral blood flow were observed in the nonresponders and the controls. In conclusion, CRT induced an increase in cerebral blood flow in patients with heart failure. This increase in cerebral blood flow was related to the improvement in left ventricular systolic function.