Experimental cerebral vasospasm arterial wall mechanics and connective tissue composition.

The elastic properties of the basilar artery were studied in control and treated dogs in which 3 ml of blood was injected intracisternally. Vascular specimens were resected transclivally as cylindrical segments and their external diameters were measured in vitro in the pressure range from 0 mm Hg to 250 mm Hg in the active condition of smooth muscle in Krebs-Ringer solution and in the passive condition in saline solution. The development of cerebral vasospasm was confirmed comparing the diameter difference between these two conditions. The experimental data indicated that vasospasm was most prominent on the 7th day after the treatment of blood injection. In the passive condition no significant dimensional change (i.e. radius and wall thickness) was observed between the control and the treated arteries at various pressure levels. These results imply that the luminal narrowing under vasospasm is not attributable to an irreversible organic change in the wall but to the constriction of vascular smooth muscle. The treated arteries are more distensible and have lower elastic moduli than the control arteries, possibly due to a change in the content of their connective tissues. These changes of the passive elastic properties of arterial walls after blood injection might be one of the factors affecting the development of cerebral vasospasm.