Aortic Longitudinal Stretch and Recoil Affect Cerebral Perfusion: Insights from a Physiologically Accurate In-Vitro...

Blood transport in the cardiovascular system depends on the interaction between cardiac dynamics and arterial function. While the left ventricle is the primary driver of flow, recent evidence suggests that longitudinal stretch and recoil of the aorta may generate a wave-pumping effect. However, the contribution of this mechanism to cerebral blood flow remains unclear.

In this study, we developed a physiologically relevant in-vitro model to isolate the effects of longitudinal aortic motion in the absence of left ventricular pumping. Aortic phantoms with varying stiffness (quantified by pulse wave velocity [PWV]) were subjected to controlled physiologically accurate cyclic stretching across a range of frequencies and amplitudes. Carotid flow waveforms were measured, and a mechanistic model was formulated based on two governing parameters: an elastic energy term associated with longitudinal stretch and a dimensionless wave condition number characterizing wave dynamics.

Our results suggest that longitudinal stretch-recoil generated a wave-pumping effect in the carotid artery, producing bidirectional net mean flow depending on wave conditions. The magnitude and direction of flow were strongly dependent on PWV, stretching frequency, and amplitude. Furthermore, the proposed mechanistic model showed strong agreement with the measured experimental data ( $r=0.827$ , $p<0.0001$ ).

Our findings demonstrate that aortic longitudinal stretch and recoil can actively contribute to cerebral blood flow through a wave-based pumping mechanism. This provides a mechanistic link among the heart, aorta, and cerebral perfusion.