Cerebral blood flow reserve in patients with syndrome X

Patients with syndrome X frequently show disorders of oesophageal motility, bronchial reactivity or impaired vasodilator capacity of peripheral vascular beds. For these reasons, it has been suggested that syndrome X may represent a generalized abnormality of vascular and non-vascular smooth muscle function, rather than an isolated coronary problem.

To measure the cerebral blood flow and cerebrovascular vasodilator reserve in syndrome X patients and in controls.

We measured the cerebral blood flow and cerebrovascular reserve in 16 patients with syndrome X [11 women, aged 59.5 +/- 10.8 years (mean +/- SD)] and in 16 age-matched healthy volunteers. No patients had evidence of stenoses of carotid and vertebral arteries on Doppler sonography. Cerebral blood flow was measured by the 133Xe inhalation method, using the initial slope index as the cerebral blood flow index. After a baseline measurement, a second cerebral blood flow measurement was performed 20 min after administration of 10 mg/kg acetazolamide intravenously. Acetazolamide is known to be a potent cerebral vasodilator. The percentage increase in cerebral blood flow after acetazolamide administration was considered an index of cerebrovascular vasodilator reserve.

Under basal conditions, both regional and global cerebral blood flow were nearly identical in the control group and in the patient group (initial slope index 50.2 +/- 3.8 versus 50.3 +/-6.2, NS). After acetazolamide administration, the cerebral blood flow increase was 29.0 +/- 14% in the patient group and 29.5 +/- 11% in the control group (NS).

Our data show that cerebral blood flow and cerebrovascular vasodilator reserve were preserved in a series of patients with syndrome X. These results are not consistent with the hypothesis of a diffuse smooth muscle disorder.