Feasibility of Zero-Dimensional-Model-Based Pulse Waveform Analysis as a Tool to Detect Ascending Thoracic Aortic Aneurysm Growth

Patients with ascending thoracic aortic aneurysms (ATAA) only have a 10-20% chance of survival upon aneurysm rupture. If aneurysm growth is detected, however, surgical repair can mitigate the rupture risk. Current computed tomography (CT)- and magnetic resonance imaging (MRI)-based surveillance methods require frequent hospital visits, increasing healthcare costs and reducing patient adherence. Pulse-based measurements, which could eventually be performed at home, are an attractive but poorly explored alternative. In this study, we investigated the feasibility of using frequency analysis of the pulse waveform to determine whether the ATAA radius or wall stiffness has changed. We first determined a correction to the standard zero-dimensional (0D) model for blood flow through curved vessels, using fluid-structure-interaction (FSI) modeling as ground truth. We then studied idealized ATAA geometries and found that changes in the size of an aneurysm led to consistent changes in the Fast Fourier Transform of the outlet pressure waveform. Furthermore, when the vessel stiffened and grew, these changes were detectable by comparing the low versus high frequency response of the outlet pressure. Similar trends were observed for FSI simulations based on retrospective study of longitudinal scans of a patient over 5 years. This study showed that analyzing the pulse waveform, as clinically measurable by surface tonometry, has potential to form the basis for an at-home method for detecting ATAA growth.