P.018 Abdominal Aortic Aneurysms and their Effect on Arterial Wave Reflection and Morphology

Abstract

Background

As already known in ancient times, cardiovascular disease can be traced by analyzing arterial (pressure) waveforms, for these can be attributed to cardiovascular properties like arterial geometry and elasticity. Consequently, we hypothesize that an abdominal aortic aneurysm (AAA) will influence arterial wave reflection and waveforms because it entails an arterial dilation accompanied by a change in arterial elasticity.

Methods

An experimental and numerical model, relying on an AAA-geometry reconstructed from patient CT-images, was designed. A silicon rubber AAA was inserted into a hydraulic bench model of the systemic circulation. Pressure and flow waves were simultaneously measured with and without aneurysm. The nature of the waves was determined with wave intensity analysis and the reflection coefficient. With the numerical model, arterial waves were simulated at the same locations. Results were verified in a preliminary study in 3 patients before and after AAA-repair.

Results and discussion

Both models demonstrated that AAA changed the nature of the reflected waves. A healthy arterial tree is characterized by positive reflections due to tapering and progressive stiffening, as was confirmed experimentally and numerically. An aortic dilation causes the opposite effect: we observed negative reflections in the upper aorta. A numerical parameter study showed that larger and more compliant AAA generated stronger negative reflections. The reflection coefficient measured in vivo increased after AAA-repair in all 3 patients, conforming the model findings.

Conclusions

Both models proved the impact of AAA on arterial waveforms elsewhere in the arterial system. These effects also appear measurable in humans.