Complementary treatments in cases of aortic dissection

Jos C. van den Berg MD PhD

Service of Interventional Radiology, Ospedale Regionale di Lugano, sede Civico
Lugano
Switzerland

Introduction


Arterial obstruction in patients with aortic dissection can be caused by the dissection flap itself (either dynamic or static), distal embolization, occlusion of a vessel arising from the false lumen, thrombosis in a region of stasis and problems caused by a pre-existing arterial stenosis.
Treatment options consist of surgical repair and endovascular repair. Stentgraft placement is indicated in cases of malperfusion of the true lumen and its branches. In some cases however, the extension of the dissection does not permit safe stentgraft placement.
This paper describes a case of extension of the intimal flap in a patient with a type A dissection into the celiac trunk, leading to occlusion.


Discussion


Aortic dissection is a life-threatening disease with a high mortality rate and an elevated incidence of early and long-term complications1. Most cases of acute type A dissection are managed surgically.
Most cases of acute type B dissection are managed medically, although open surgery or stent-graft placement is sometimes performed. Patients with type B or surgically treated type A dissection may develop vascular complications such as mesenteric or peripheral ischemia, which cannot be managed medically. In these cases arterial obstruction can be caused by the dissection flap itself (either dynamic or static), distal embolization, occlusion of a vessel arising from the false lumen, thrombosis in a region of stasis and problems caused by a pre-existing arterial stenosis2, 3.
Treatment options consist of surgical repair and endovascular repair. Stentgraft placement is indicated in cases of malperfusion of the true lumen and its branches. In some cases however, the extension of the dissection does not permit safe stentgraft placement. The contraindications for endovascular treatment using a stentgraft are most often related to anatomic considerations. Stent-graft placement requires adequate vascular access (sufficient diameter of the iliac artery and abdominal aorta without severe tortuosity), and an aortic lesion without excessive tortuosity and whose neck extends more than 15 mm above the celiac artery and is more than 5 mm distal to the left subclavian artery, without mural thrombus (more than 50% of patients present with thrombosis of the false lumen) and dilatation4. Other contraindications are: a tear too proximal to crucial branch vessels, inadequate seal of the stentgraft or unavailability of an adequate size stentgraft. In cases of ischemic complications related to aortic dissection where contraindications for stentgraft placement exist, alternative treatment options such as fenestration and stent placement should be employed5. Goal of these therapies is to allow outflow from the false lumen, to relieve branch vessel obstruction, to reduce intraluminal pressure and to reduce the risk of extension of the dissection.

Treatment options


Fenestration is a method to decompress the hypertensive false lumen by creating a hole in the distal part of the dissection flap, and thus augmenting flow in the true lumen (and its branches at risk)6. Fenestration is the treatment option of first choice.
Two different techniques to create and enhance communication between the true and false lumen exist:
Balloon technique:
With this technique a guidewire is placed across an existing communication between false and true lumen (either going from true to false or vice versa); a large size balloon (>15 mm) is used to enlarge the pre-existing hole.
Creation of a novel communication by puncturing the intimal flap using the back-end of a guidewire or needle systems as used in TIPS procedures; puncture guidance can be performed using a loop snare in false lumen as target, using multiplanar or 3D rotational angiography, TEE or IVUS; subsequently the puncture hole is enlarged as described above.
Scissor technique:
With this technique the arterial system is accessed at a point beyond the dissection with a 6F or 7F introduction sheath; selective canulation of the true and false lumen is performed, and guide wires are left in place; a guiding catheter is then advanced over both guidewires and will tear the intimal flap in a longitudinal fashion5.

It is of utmost importance to measure intra-arterial pressure within the true and false lumen. The aim is to reduce the pressure gradient to less than 5 mm Hg. In case this objective can not be reached a second angioplasty with a larger balloon or a second fenestration can be performed.
Complications of fenestration procedures include dehiscence of intimal flap (on CTA presenting as a tube-in-tube sign), aneurysm formation, transmural perforation and finally propagation of dissection7, 8.
Stent placement:
Indications for stent placement are the presence of static dissection (i.e. extension of dissection up to and/or into aortic side branch in absence of re-entry tear, resulting in constriction of lumen) into a branch vessel only. This can be performed by direct access, in a way similar to stent placement in cases of atherosclerotic stenotic disease. In case the occlusion can not be recanalized in an antegrade fashion, collaterals can be used to perform a retrograde recanalization.
Other indications are persisting pressure gradient after fenestration, the presence of significant thrombus in the false lumen (this increases the risk of embolization during fenestration procedures), and finally failure to perform a fenestration.
It has to be kept in mind that stent placement (especially in the false lumen) might compromise future thoracic surgery.
Technical success can be achieved in up to 90% of cases, with a clinical success of 43% to 91%6, 9. About one-third of patients die in cases of visceral artery involvement.

Conclusion


Aortic dissection can be complicated by occlusion of visceral side branches that may lead to life-threatening visceral ischemia. Several surgical and endovascular treatment options are available.
 


References


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