Endoleaks (Type I-V)
An endoleak is a fairly common complication of endovascular aneurysm repair (EVAR) surgery, a surgical technique used primarily to heal abdominal aortic aneurysm (AAA). The procedure involves placing a stent graft within the aorta (the largest blood vessel in the body) to restore aortic functioning without having to operate directly on the aorta.
Endoleaks have been found to occur in as many as 40% of EVAR patients during surgery after placement of the stent, and have been documented in 10% to 30% of patients postoperatively during a visit to their surgeon’s office.
How Do Endoleaks Occur?
An endoleak occurs when blood persistently leaks back into the aneurysm sac outside of the endograft. Usually, an endoleak causes no symptoms at all and is often found during a routine follow-up visit with a vascular surgeon after one has undergone EVAR surgery. An endoleak is usually detected by imaging tests such as a CT angiography or ultrasound.
Endoleaks are commonly referred to as the “Achilles heel” of EVAR, as their occurrence often seems inevitable, resulting from the presence of pre-existing patent branch vessels that originate in the aneurysm sac.
About 30% of patients with PAD die within 5 years, usually due to an ischemic coronary event.
Types of Endoleaks
The five types of endoleaks are typically classified by their respective causes and treatments:
Type I: When the stent graft fails to adequately seal the vessel wall, blood can flow inside the aneurysm sac, increasing the pressure within the sac, which can ultimately cause it to burst.
Type II: The most prevalent type of endoleak stemming from an increase in pressure in the side branches of the aorta that push blood back into the less pressure-filled aneurysm sac, this type of endoleak is generally harmless although its behavior is often unpredictable.
Type III: Caused by faulty endograft materials, by stent graft fracture, or by poor positioning of endograft components. As with type I endoleaks, a type III endoleak generates increased pressure in the aneurysm sac that can lead to rupture. Type III endoleaks also need to be treated urgently.
Type IV: Due to the porous nature of certain graft fabrics, a type IV endoleak can happen shortly after some EVAR surgeries. It normally resolves on its own or with the help of anti-coagulant medication.
Type V: Known as endotension, a type V endoleak remains somewhat of a mystery as aneurysm sac expansion continues in the absence of a clear leak source. One theory explains that graft permeability enables pressure to seep through to the aneurysm sac, causing expansion.
How Are Endoleaks Treated?
Treatment for endoleaks will depend on the category of the endoleak.
Type I endoleaks are normally healed by improving the seal within the artery or by shifting it to a better location. This is done through the use of cuffs or capped stents that are placed at the end of the exposed graft. If these measures fail to secure the leak, especially if the leak occurs during the EVAR procedure, open surgery may be needed to effectively correct the situation.
Several options exist to treat type II endoleaks:
- Sometimes a physician will recommend waiting to see if the endoleak clears up on its own, and if it persists, it is repaired through embolization of the branch vessel with coils or glue.
- A frequently employed method, transarterial embolization, uses microcatheter techniques to release clot-stimulating substances to block the endoleak. The procedure can be time-consuming, highly technical, and can involve a higher rate of radiation exposure.
- More rare procedures involve branch vessel ligation and open surgical intervention.
Type III endoleaks are normally resolved with additional materials to reinforce the lining of the endograft and close the defective part of the graft. If this fails to fix the problem, open surgery can act as a last resort solution.
Type IV endoleaks often clear up on their own once blood clotting returns to normal. No other surgical procedures are normally required.
Treatment for type V endoleaks is complicated as the cause is so hard to detect. Surgeons generally will attempt to reinforce the endograft with extension cuffs, and if that fails, open surgery may be recommended.