Percutaneous transluminal angioplasty in a canine model of cerebral vasospasm: angiographic, histologic, and pharmacologic evaluation.

BACKGROUND

Cerebral vasospasm following subarachnoid hemorrhage (SAH) is one of the leading factors that deteriorate the clinical outcome after aneurysmal surgery. Percutaneous transluminal angioplasty (PTA) is a method to directly dilate the constricted vessel using the intravascular neurosurgical technique.

METHODS

Angiographic, histologic, and pharmacologic evaluations related to PTA are presented, using a canine double-injection model of SAH. In angiographic evaluation, we studied the effect of PTA performed on day 1, 4, or 7 of SAH. We performed sequential histologic study by light microscopy using the same for the angiographic evaluation. In pharmacologic evaluation, we measured in vitro isotonic constrictive force using two vasoconstrictors immediately after PTA on normal basilar arteries (control group) and basilar arteries on day 7 of SAH.

RESULTS

In angiographic evaluation, we observed the effective dilation of spastic artery immediately after PTA and saw no recurrence of vessel constriction when PTA was performed on day 7 of SAH. However, the preventive effect of PTA was inconsistent when it was performed earlier after SAH (days 1, 4). In histologic evaluation, PTA segments immediately after PTA showed denuding of endothelial cells and stretching of the internal elastic lamina without disruption of the muscle layer. In pharmacologic evaluation, there was no difference in isotonic constrictive force created by vasoconstrictors between the PTA and non-PTA segments without SAH. However, there was a statistically significant reduction of isotonic constrictive force on the PTA segment with SAH.

CONCLUSIONS

We suggest that the mechanism of PTA vasodilation in vasospasm after SAH may result from mild functional changes in the vascular wall when PTA was applied on day 7 of SAH. The functional changes would not be adequately induced to prevent recurrence of vasoconstriction when PTA was applied soon after SAH.