Flow-independent dynamics in aneurysm (FIDA): pressure measurements following partial and complete flow impairment in experimental aneurysm model

Abstract

Background: There have been growing concerns regarding delayed aneurysm rupture subsequent to the
flow-diverting stent deployment. Therefore, more investigations are needed regarding hemodynamic
changes secondary to flow-diverting stent deployment.
Objective: To study intra-aneurysmal and perianeurysmal pressures after partial and complete flow
impairment into the aneurysm.
Methods—A silicone model of an 8-mm-sized aneurysm (neck diameter: 5 mm, vessel size: 4 mm) was
used. The aneurysm wall was encapsulated and sealed within a 5 ml syringe filled with saline and a pressure sensor guide wire (ComboWire, Volcano Corp.) to detect pressure changes in the perivascular compartment (outer aneurysm wall). A second pressure sensor guide wire was advanced inside the aneurysm
sac. Both pressure sensors were continuously measuring pressure inside and outside the aneurysm under
pulsatile flow under the following conditions: 1) baseline (reference); 2) a 16 mm by 3.75 mm flow-diverting stent (ev3/Covidien Vascular, Mansfield, MA) deployed in front of the aneurysm; 3) two flow-diverting
stents (16 mm by 3.5 mm) were deployed; and 4) a covered stent (4 mm by 16 mm VeriFlex coronary
artery stent covered with rubber sheet) was deployed.
Results: Mean (±SD) baseline pressures inside and outside the aneurysm were 53.9 (±2.4) mmHg (range
120–40 mmHg) and 15.4 (±0.7) mmHg (range 40–8mmHg), respectively. There was no change in pressure
inside and outside the aneurysm after deploying the first and second flow-diverting stents (partial flow
impairment) and it remained at 53.9 (±2.7) mmHg and 14.9 (±1) mmHg for the pressure inside and outside
the aneurysm, respectively. The pressure recording from outside the aneurysm dropped from 15.4 (±0.7)
mmHg to 0.3 (±0.7) mmHg after deploying the covered stent (complete flow impairment). There was no
change in pressure inside the aneurysm after deploying the covered stent. Mean (±SD) pressure within the
aneurysm was 55.1 (±1.7) mmHg and it remained 54.7 (±1.7) mmHg after covered stent deployment.
Conclusion: Our findings suggest a major discordance between the pressures within the aneurysm and
partial or complete flow impairment (flow independent). The outer wall pressure is reduced after covered
stent placement. These finding may assist clinicians in better understanding of aneurysm hemodynamics
and rupture after flow-diverting stent deployment.