  Rupture of aortic aneurysms is by far the most fatal heart disease, with a
mortality rate exceeding 80%. There are no reliable clinical protocols to
predict growth, dissection, and rupture because the fundamental physics driving
aneurysm progression is unknown. Here, via in-vitro experiments, we show that a
blood-wall, fluttering instability manifests in synthetic arteries under
pulsatile forcing. We establish a phase space to prove that the transition from
stable flow to unstable aortic flutter is accurately predicted by a flutter
instability parameter derived from first principles. Time resolved strain maps
of the evolving system reveal the dynamical characteristics of aortic flutter
that drive aneurysm progression. We show that low level instability can trigger
permanent aortic growth, even in the absence of material remodeling.
Sufficiently large flutter beyond a secondary threshold localizes strain in the
walls to the length scale clinically observed in aortic dissection. Lastly,
significant physical flutter beyond a tertiary threshold can ultimately induce
aneurysm rupture via failure modes reported from necropsy. Resolving the
fundamental physics of aneurysm progression directly leads to clinical
protocols that forecast growth as well as intercept dissection and rupture by
pinpointing their physical origin.
