Hypertension has long been known to be a causative factor in intracranial hemorrhage, but how much of that is from direct effect? Piechnik and colleagues have investigated this concept via observation of the pressure required for rupture of cadaveric cerebral arteries. 31 vessel segments of the main cerebral arteries at the level of the circle of Willis were collected. Donor age ranged from 24-80 years, and vessel segments averaged 1-2cm in length and 2.6mm in diameter. Segments were mounted on a flared needle, and the open end and perforators were clipped/ligated. Saline was used to pressurize the vessels until rupture, and vessels were then inspected microscopically.
The average rupture pressure was 2.35 +/- 0.55atm, which authors note exceeds the highest observed systolic blood pressure seen in en-vivo by several times. Pressure and vessel dilation at rupture correlated inversely to age, with vessels from older donors breaking at lower pressures and % dilatation. Compensating for age trends, ANOVA did not reveal significant differences between rupture pressures and vessel location, presence of bifurcation and type of rupture. Similarly, the presence of plaque (n=3) or aneurism (n=2) did not result in any statistically significant effect on rupture pressure or maximum vessel distensibility.
Observed rupture pressures were well above physiologic stress, thus making the case that additional pathology is required for vessels to be prone to bleeding, and that the known correlation of HTN and ICH is likely secondary (at least to some degree) to chronic changes. It would be interesting to see similar experiments directed at perforators, as these vessels are often implicated in IPH. Age does appear to play a significant role in vessel compliance, which reinforces the need for aggressive stroke prevention in the elderly, and may additionally play a role in the setting of angioplasty or intervention in this population.