Our goal was to evaluate physical factors in the initiation and propagation of dissections in human aortas. Aortic dissection was simulated in 21 open unpressurized human autopsy aortas by infusing dyed isotonic saline into the media at constant flow. Pressure during growth of the fluid filled cavity was monitored and correlated with volume to give pressure-volume curves, from which distensibility, peak pressure, and work data were calculated. Dissections in specimens occurred at a very high nonphysiological mean pressure of 79 ± 29 (SD) kPa (596 ± 214 mmHg). Age and tear depth had no significant effect on medial strength of human aortas but sex, location and atherosclerotic plaque formation did (p < 0.05). The mean pressure value for the female abdominal fibrous/calcified group (92 ± 30 kPa, 691 ± 222 mmHg) differed from that of the male abdominal fibrous/calcified group (69 ± 36 kPa, 508 ± 269 mmHg). We also observed a significant difference between the male thoracic fibrous calcified (80 ± 31 kPa, 601 ± 230 mmHg) and male abdominal fibrous/calcified (68 ± 36 kPa, 508 ± 269 mmHg) groups. Significant differences were observed between the female fatty/normal (75 ± 25 kPa, 562 ± 187 mmHg) and fibrous/calcified (91 ± 23 kPa, 685 ± 176 mmHg) groups of the thoracic aorta and between the male fatty/normal (86 ± 23 kPa, 650 ± 169 mmHg) and fibrous/calcified (68 ± 36 kPa, 508 ± 269 mmHg) groups of the abdominal aorta. Distensibility data showed no trends. It is probable that dissection does not occur spontaneously in the absence of a connective tissue disorder and/or surgical procedure. Atherosclerosis is not responsible for dissection initiation but may alter the propagation of dissection.

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