Endologix Ovation

Deployment

After delivery of the stent graft, it is unsheathed and the proximal nitinol stent is deployed in two stages with the RO markers ensuring proper positioning of the graft ( Fig. 7.3B ). After the release of the first knob, the mid-crown is deployed. The stent graft can still be repositioned at this time. It is prudent to start deployment higher than the intended final position, since it is easier to pull the stent graft down than to push it up. After the second knob is released, the suprarenal stent is completely deployed, anchoring the stent graft. The polymer is mixed in the two syringes of the polymer kit and infused using the autoinjector ( Fig. 7.3A ). The polymer begins to fill the stent graft, inflating the sealing ring against the aortic wall. The autoinjector exerts a constant pressure against the aortic wall allowing the seal to conform to the aortic wall. Holding the stent delivery system or applying forward pressure on it is not recommended. The stiff wire is withdrawn into the body of the graft to facilitate conformance of the stent to native aortic anatomy, especially when acute angulation is present. The deployment of the main body is completed by turning the third knob to disconnect the filling tube from the stent graft.

Instructions for use (IFU)

According to the IFU, the anatomic criteria for the use of the Ovation stent graft include proximal aortic diameter between 16 and 30 mm at 13 mm below the inferior most renal artery, with an aortic angle of ≤60 degrees if proximal neck is ≥10 mm and ≤45 degrees if proximal neck is <10 mm. There should be at least 10 mm iliac landing zone with diameters between 8 and 20 mm. Patients with known allergy to the device materials (including PTFE, polyethylene glycol (PEG)-based polymers, fluorinated ethylene propylene [FEP] or nitinol) should not be treated with the Ovation stent graft.

Polymer-related complications

As mentioned above, the Ovation stent graft is contraindicated in patients who are allergic to device materials including PTFE, PEG, or nitinol. There have been reports of inadvertent leakage of polymer into the systemic circulation with resulting allergic reactions including anaphylaxis. In the majority of cases, the exact cause of the leakage was not identified and was attributed to defects in the polymer kit system.

To prevent polymer-related complications, the IFU should be followed when deploying the stent. The following steps and key points should be considered to prevent polymer-related issues:

• After deployment of the suprarenal stent, the delivery system should not be pulled as it may cause inadvertent detachment of the polymer fill connecter from the main body leading to leakage of the polymer into the blood.

• The delivery system should not be detached prematurely (time to polymerize is 20 minutes for the TriVascular Fill Polymer Kit or 14 minutes for the CustomSeal Kit) to prevent leakage of the polymer.

• The patient’s body temperature should also be considered. The polymer is designed to cure at core body temperature of 37°C and might take longer at lower temperatures. If the core body temperature is lower than 35°C, it may require at least one additional minute per degree below 35°C prior to disconnection.

• If there is an error in mixing or transferring the polymer or delay in infusing after mixing (3 or more minutes after mixing if using the TriVascular Fill Polymer Kit or injection has been delayed 2 or more minutes using the CustomSeal Kit), the polymer should be discarded and a new kit opened.

• The polymer should be infused using the autoinjector only; hand injections can damage the stent causing delamination of the polymer channels.

• The filling of the polymer should be initially observed under fluoroscopy. Lack of filling of the polymer channels or rapid emptying of the syringe may indicate that the polymer is not being infused into the stent and may be leaking into the blood.

If there is suspicion or evidence of leakage, the autoinjector and the polymer fill syringe should be immediately detached from the delivery system to ensure patient safety.

In case of allergic reactions, standard treatment (antihistamines, steroids, vasopressors, airway protection) should be administered.

Type IA Endoleak

Type IA can result from incomplete or lack of filling of the sealing rings or secondary to in-folding of the sealing ring. The IFU and the key points described in the previous section should be followed to prevent and minimize the chances of a type IA endoleak.