Effects of angioplasty upon carotid sinus mechanical properties and blood pressure control in the dog.

The effects of vein patch angioplasty of the carotid sinus upon carotid sinus control of blood pressure and carotid sinus mechanical properties were studied in nine vagotomized dogs. Pressures in the isolated carotid sinuses were increased from 60 to 180 mm Hg in steps of 30 mm Hg, and the resulting reflex changes in mean aortic pressure were measured both before and after unilateral angioplasty. Angioplasty significantly decreased aortic pressure for carotid sinus pressures above 60 mm Hg, decreased the calculated carotid sinus reflex set point pressure, and increased the range of control of arterial blood pressure together with the maximal capacity of the arterial baroreceptors to effect vasoconstriction. In five dogs, concomitant changes in carotid sinus diameter were measured. From the latter, together with accompanying changes in sinus wall geometry, were calculated the tension-strain modulus of elasticity of the carotid sinus wall, together with the radial displacement of the media-adventitial junction. Calculated increases in the latter were consistent with the observed increased effectiveness of the carotid sinus baroreceptors after angioplasty. It was concluded that the modification of blood pressure and its control was predominantly due to the surgical exaggeration of normal carotid sinus geometry accompanied by modest changes in carotid sinus wall mechanical properties.