Blood flow in abdominal aortic aneurysms indicates severity and threat

The aorta, the major vessel that supplies blood to the body, runs from the heart through the chest and abdomen. An abdominal aortic aneurysm (AAA) occurs when the lower part of the aorta becomes inflamed and enlarged. AAAs can develop slowly and quickly, often proving fatal if they rupture. Clinicians are faced with a dilemma of intervening or surveilling, so routine inspection and monitoring is required.

Monitoring flow features in AAA can demonstrate severity and deviation, but it is not currently used in clinical practice. Norouzi et al. investigate flow physics modeling using spectral proper orthogonal decomposition (SPOD) and identify its role in evaluating AAAs.

“SPOD is an ideal tool for modeling complex flows of this kind and a powerful alternative to methods used in similar applications,” said author Shahrzad Norouzi. “We demonstrate that the half-life time (an indicator for particle residence) in AAA models can distinguish severity, suggesting a promising metric for AAA assessment and decision-making.”

The researchers applied SPOD to a healthy abdominal aorta and three models of AAAs, finding AAA severity is based on underlying flow. Aneurysm expansion ensures flow becomes increasingly complex, accompanied by larger vortical structures, oscillatory flow rates and regions of flow stagnation.

“Using this technique, and with the help of future studies, a model database consisting of many more cases of AAAs can be created to feed learning algorithms and create a predictive flow model,” said Norouzi. “This will ultimately help to better understand cardiovascular flows and potentially lead to developing new parameters applicable to diagnosis, severity assessment and better patient care.”

Source: “Flow examination in abdominal aortic aneurysms: Reduced-order models driven by in vitro data and spectral proper orthogonal decomposition,” by Shahrzad Norouzi, Arnaud Le Floc’h, Giuseppe Di Labbio, and Lyes Kadem. Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0069560 .