Thoracic endovascular aortic repair (TEVAR), first performed in 1992, has become the treatment of choice for the majority of thoracic aortic pathologies, including thoracic aortic aneurysms (TAAs) and complicated Type B aortic dissections (TADs).
Presence of an endoleak is one of the most common reasons for early or late reinterventions and/or treatment failure following TEVAR. Endoleaks can be classified into four categories. A fifth category, called endotension, refers to aneurysmal sac pressurization without documented evidence of endoleak ( Fig. 19.1 ). Endoleaks after TEVAR have been reported in 15%–30% of cases. TEVAR failure in TAAs is most often a result of endoleaks, and failures in TADs are mainly because of persistent false lumen perfusion. The key element in prevention of endoleak formation is careful preoperative planning. However, once endoleaks develop, it is important to understand the cause of the endoleak as well as the anatomy of the aorta.
This chapter focuses on different techniques for treating endoleaks following TEVAR.
Type I Endoleaks
Type I endoleaks originate from the sealing zones of the endograft and are further subdivided into proximal (Type Ia) or distal (Type Ib). Early Type I endoleaks are most often a result of an inadequate sealing zone in severely angulated, highly calcified aortic arches with increased thrombotic burden and vessel wall irregularity. Graft in-folding secondary to more than 30% oversizing and bird-beak configuration ( Fig. 19.2 ) are two very common reasons for Type Ia endoleaks. Progression of aortic disease is the cause of late Type I endoleaks.
If Type I endoleak is identified on completion angiogram, the first step is balloon angioplasty. This corrects potential in-folding of oversized grafts. Nonetheless, this is not a simple maneuver and requires caution, particularly in dissection cases, where there is a risk of retrograde dissection. In addition, during balloon inflation, graft migration can occur as a result of windsock effect. This can be prevented by lowering blood pressure and ensuring good support from an introducer sheath. Rapid ventricular pacing is occasionally necessary.
Bird-beak formation was more frequently seen in early generation devices. This can potentially lead to complete collapse of the stent graft, with the risk correlating to the length of the beak. The endoleak secondary to bird beak is approached with a combination of interventions. Proximal stent-graft placement in conjunction with coverage and coil embolization of the left subclavian artery is often sufficient to correct the condition. However, placement of a proximal extension can be hazardous, because it may interfere with the left carotid artery. To minimize the risk of carotid coverage and to optimize stent graft placement, a sheath or a guidewire is introduced from the left carotid into the ascending aorta. This can be very helpful for bail-out stenting if unintentional coverage of the carotid occurs or intentional coverage is necessary for snorkel placement.
If a Type Ia endoleak results from insufficient neck length and placement of an extension cuff is not possible without cervical debranching, the use of Heli-FX EndoAnchor has been occasionally successful. Use of the active fixation prevents graft migration in cases of complex aortic anatomy. Placement of a Palmaz stent in a short neck to eliminate Type I endoleak is unlikely to be successful. The treatment of perioperative Type Ib endoleak is balloon angioplasty and, if not successful, placement of an extension cuff. If coverage of the celiac trunk is needed, we use the sandwich technique to maintain celiac patency. However, if the celiac orifice is stenotic, it can be covered. The chimney or sandwich techniques are becoming more common procedures, allowing creation of prolonged proximal and distal landing zones without compromising perfusion of the branches.
Another option is transcatheter embolization of the Type I endoleak. Published experiences include endoleak embolization using coils, cyanoacrylate, and Onyx.
Open conversion, with partial or full extraction of the stent graft, allows easy access to the site of the endoleak but carries a particular high risk in old, frail patients who represent the majority of the population with aortic disease. In addition, the presence of the stent graft can complicate the repair, and hypothermic circulatory arrest may be necessary with modification of standard exposure.
Type II Endoleaks
Type II is the most frequent form of endoleak following TEVAR. Common sources of Type II endoleaks include the intercostal and bronchial arteries. Intraoperative Type II endoleaks are not routinely treated, since most resolve spontaneously. Nonetheless, endoleak from the subclavian artery may require special attention because of the large diameter of the vessel and its relationship to the aortic arch. The vessel can be easily accessed via a retrograde approach from the left brachial artery, and embolization with an Amplatzer plug or coils can be performed. A transthoracic approach for embolization of the subclavian artery can be used if a transbrachial approach is not possible (inadvertent ligation of subclavian artery distal to vertebral artery orifice, Fig. 19.3 ). The subclavian artery can be covered with a low incidence of side effects. However, revascularization with carotid–subclavian bypass is mandatory in patients with prior CABG with LIMA bypass, dominant left vertebral artery, or pre-existing incomplete posterior circulation.