Introduction
A recent randomized clinical trial showed that blood pressure lowering treatment reduced a stroke recurrence in patients with a prior stroke or transient ischemic attack 1 . However, systemic blood pressure lowering may reduce cerebral perfusion pressure. In some patients with severe occlusive vascular lesions, blood pressure lowering may be harmful in stroke prevention. In this study, we tested our hypothesis that systemic blood pressure may affect the cerebral vascular reserves (CVR).
Methods
We retrospectively investigated 52 consecutive patients who repeatedly underwent I-123 IMP SPECT with acetazolamide (ACZ) challenge test during 3 years (mean interval of the SPECT study was 557 ± 253 days, male/female was 35/17, mean age was 64.9 ± 8.4 years old). Before the SPECT study, each patient underwent neurological and neuroradiological evaluations (duplex carotid ultrasonography, MRI, and MR angiography). We measured systemic mean arterial blood pressure (MABP) at each examination time. The CVR was defined as follows; CVR (%) = (counts at ACZ loading SPECT - counts at resting SPECT) / counts at resting SPECT * 100. The CVR was classified as follows; normal (CVR >= 34.1%), mild impairment (25.3 % < CVR < 34.1 %), or severe impairment (CVR <= 25.3 %). The above dividing CVR thresholds were determined as mean CVR - 1SD and mean CVR - 2SD of control group. We categorized the patients into 3 groups according to the longitudinal changes in the CVR classification as follows; the CVR classification was worsened or the CVR was impaired in both studies (Group 1), the CVR classification was improved (Group 2), or the CVR was both normal (Group 3).
Results
17 of 52 patients were classified as Group 1. In this group, their follow up MABP (93.3 ± 12.3 mmHg) was significantly lower than their initial MABP (99.2 ± 9.9 mmHg, p < 0.05). 11 and 46 patients were classified as Group 2 and Group3, respectively. In Group 2 and Group 3, their follow up MABP (97.6 ± 9.2 mmHg, 99.2 ± 12.3 mmHg, respectively) was not significantly changed from their initial MABP (94.6 ± 9.0 mmHg, 98.3 ± 11.9 mmHg, respectively). The frequency of arterial occlusion in Group 1 (11 of 17 patients; 65%) was significantly higher than that in Group 2 and 3 (4 of 11 patients; 36%, 8 of 24 patients; 33%).
Conclusion
The present study demonstrated that systemic blood pressure reduction may impair cerebral vascular reserves. Patients who had vascular occlusion must be carefully treated in blood pressure lowering treatment.