Experimental Dissection of Media of Aorta by Pressure
ITS RELATION TO SPONTANEOUS DISSECTING ANEURYSM
The pressure required to produce intramural dissection was determined by injection of water into the media of strips of aorta obtained at postmortem examination. The mean pressure required reached a maximum in the second and third decades and decreased gradually thereafter. No differences in the pressure required was noted when comparisons were made by race, sex, different segments of the aorta, different strata of the media, or in the region of atherosclerotic lesions. Pregnancy (postpartum state) did not decrease the resistance in two instances. A slight increase in the pressure required was observed in the aortas of patients with hypertensive disease, and a marked increase was encountered in the presence of syphilitic aortitis. The resistance of the aorta in spontaneously occurring dissecting aneurysm was variable; one case had a normal resistance while the other was impaired.
The authors postulate that a solitary focus of medial degeneration strategically located is an adequate stimulus for dissection. Subsequently, rupture of vasa vasorum into this weakened area results in a rapidly expanding bleb. The pressure required to produce further enlargement of the bleb will vary inversely with its diameter, thus tending to extend the dissection. This mechanism may explain the frequent finding of an histologically normal aorta in random sections from cases with extensive intramural dissection.
- Received November 17, 1961.
- © 1962 American Heart Association, Inc.