Biomechanical Considerations in the Unruptured Cerebral Aneurysm Study (UCAS Japan): Rupture Risk and True Stress of Wall

Fumio Nogata,Nigishi Hotta,William R Walsh,Tetsuya Mouri,Takakahiko Kawamura,Kenji Kagechika,Yoko Kawamura,Hiroyuki Morita,Yasunari Yokota,Yoshiyuki Uno

doi:10.4236/jbm.2021.910015

Abstract

When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effectiveness of diagnostic and therapeutic devices and the risk-benefit ratio of patients, caregivers, and healthcare professionals. The guidelines evidence-based of large clinical data for this purpose are presented by national medical societies. As one of the rupture risk indicators, there is the hazard risk ratio derived by the UCAS Japan research group based on the statistical method of 6697 aneurysms in 5720 patients with cerebral aneurysms of 3 mm or more. Therefore, we investigated the biomechanical significance of this hazard risk ratio using a spherical aneurysm model. It was revealed that 1) the reason why the frequency of aneurysm rupture is relatively high up to about 10 mm, 2) the UCAS hazard risk ratio corresponds to stress of the aneurysm wall, and the true stress can be calculated by multiplying the patient’s blood pressure, and 3) the factors that cause the daughter’s sac (irregular protrusion of the aneurysm wall). In addition, our two methods for measuring the strength of the blood vessel wall of an individual patient were described.

Highlights

An aneurysm occurs in locally weakened part of the blood vessel wall, and the part that expands to more than 1.5 times the size of normal arterial diameter is called aneurysms [1] [2] [3]
We demonstrated that the hazard risk value derived based on the clinical data statistics published by the Unruptured Cerebaral Aneurysm Study (UCAS) Japan investigators corresponds to the stress of a spherical aneurysm model’s wall
The biomechanical signification of the hazard risk ratio of 6697 unruptured aneurysms reported by the UCAS Japan research group based on statistical method was discussed using a spherical aneurysm model

Summary

Introduction

An aneurysm occurs in locally weakened part of the blood vessel wall, and the part that expands to more than 1.5 times the size of normal arterial diameter is called aneurysms [1] [2] [3]. Several guidelines including the latest issues have been published that provide comprehensive evidence-based recommendations for managing patients with unruptured aneurysms by the American Heart Association/Stroke Association [6], the European Society of Cardiology (ESC) [17] [18], and the Unruptured Cerebaral Aneurysm Study (UCAS) in Japan [19] [20] [21] These guidelines aim to provide guidance for making the best final decision taking into consideration the effects of specific diagnostic or therapeutic measures and the risk-benefit ratio by patients, caregivers and responsible healthcare workers

Methods

Results

Conclusion