Blood pressure, fatigue, and the pathogenesis of aneurysmal subarachnoid hemorrhage

BackgroundEndovascular embolization and BP reduction appear to protect cerebral aneurysms from rupture, although they do not totally eliminate aneurysm wall stress as does surgical clipping. We investigate the possible mechanisms of rupture to offer an explanation for this.MethodsFatigue modeling of cerebral aneurysms using BP as the source of wall stress loading and calculating the increase in cycles to failure produced by a reduction in stress loading.ResultsA modest reduction in the stress loading of aneurysms leads to a disproportionately large increase in the time taken for them to rupture. This result is based on the following assumptions and is thus restricted to aneurysm for which they may reasonably be true.1.Fatigue is the dominant mode of failure.2.The final decline in strength is rapid.3.The aneurysm lasts at least 6 weeks before rupturing.ConclusionsA slight reduction in the stress on aneurysm walls can dramatically reduce their risk of rupture.