Managing False Lumen Patency in Chronic Thoracic Aortic Dissecting Aneurysms With Coil Embolization

CT

computed tomography

SMA

superior mesenteric artery

TEVAR

thoracic endovascular aortic repair

Anti-impulse therapy, which focuses on controlling the heart rate and blood pressure, is the management of choice for uncomplicated type B aortic dissection. Despite being a rare disease with an incidence of 5 to 15 per 100,000 persons per year, 25% to 40% of patients with type B aortic dissection have a complicated case. This presents with unrelenting pain, organ malperfusion, rupture, and/or aneurysmal degeneration.¹  Thoracic endovascular aortic repair (TEVAR) has become an integral modality of treatment for this condition, with the INvestigation of STEnt Grafts in Aortic Dissection (INSTEAD) trial demonstrating improved positive aortic remodeling, reduced mortality from aortic events, and reduced progression of dissection at 2 to 5 years posttherapy.² 

The goal of treatment is to induce adequate thrombosis of the false lumen. Persistent flow into the false lumen pressurizes the aorta, which can lead to aneurysmal degeneration and risk of aortic rupture.³  This may occur from retrograde false lumen flow along the stented true lumen caused by distal reentry tears or from perfusion caused by branches off the false lumen into the abdominal aorta.⁴ 

The literature includes several techniques that address this complication. Kölbel et al,⁵  for example, described the candy-plug technique, where a modified covered stent was deployed into the false lumen, followed by a vascular plug at the waist to occlude distal backflow. However, this can cause luminal narrowing and is not suitable for multiple distal entries or when the visceral artery originates from the false lumen. The same author also described the knickerbocker technique, which is the placement of an oversized thoracic tubular endograft followed by controlled rupture of the dissection membrane in the midsection of the graft.⁶  This case report describes the successful treatment of the patent false lumen using coil embolization, as an adjunct to TEVAR. The patient has provided informed consent.

This is a case of a 59-year-old male with a history of hypertension, lumbar disc disease, and hypothyroidism who was transferred to SUNY Upstate Medical University with an acute complicated type B thoracic aortic dissection (Fig. 1). The dissection flap originated distal to the left subclavian artery, causing significant true lumen compromise and resulting in superior mesenteric artery (SMA) and right renal artery occlusion (Fig. 2). The dissection extended down to the proximal right common iliac artery. An emergency aortogram was performed to place a Zenith Dissection Endovascular Graft (Cook Medical), a 34 × 154-mm thoracic endograft, just distal to the left subclavian artery. Overlapping Omnilink Elite (Abbott) bare metal balloon-expandable stents (6 × 59-mm stent followed by a 7 × 59-mm stent) were placed in the SMA to regain luminal patency. A right hemicolectomy was performed for bowel ischemia. The patient recovered well and was discharged to the rehabilitation unit.

Three months postoperatively, the patient presented with chest and abdominal discomfort. Computed tomography (CT) angiogram demonstrated evidence of a patent false lumen distal to the stent graft with an increase in aortic diameter by 1 cm since the index scan. To address this, a tapered Zenith Dissection Endovascular Graft (Cook Medical) 34 × 159-mm aortic stent graft was placed distally, overlapping the previously placed graft. Effort was made to avoid covering the distal lumbar branches and reduce the risk of spinal ischemia, with spinal drains used intraoperatively. The right hypogastric was patent but had diminished flow, and the left hypogastric was occluded.

Despite the extension, the patient presented 10 months later with back pain. CT angiogram showed enlargement of the type Ib endoleak, which was causing retrograde filling of the false lumen and enlargement of the thoracic aorta (Fig. 3). At this time, it was decided to address the false lumen. An additional Zenith Alpha thoracic stent graft (Cook Medical) measuring 34 × 161 mm was placed distally, and coil embolization of the false lumen was performed using 6 Penumbra 60-cm packing coils (Fig. 4 and Fig. 5). Adequate wall apposition of the distal stent was noted, with complete exclusion of the false lumen. The celiac and SMA stent patency was preserved.

The patient did well until 6 months later, when he developed symptoms of chronic mesenteric ischemia with postprandial pain. He also reported bilateral lower-extremity weakness and occasional numbness as well as limited ability to ambulate short distances. Aortic angiography revealed severe stenosis of the distal and proximal aspects of the SMA stent. Balloon angioplasty of the previously placed stents with the placement of a covered stent in the proximal SMA resolved these symptoms. Magnetic resonance imaging showed T2 hyperintensity in the central spinal cord extending from T10 to T11 to the conus medullaris at L2, which could represent spinal ischemia.

At the 1-month postoperative visit, a CT angiogram was performed, demonstrating stable sac size and thrombosis of the false lumen with patency of the visceral stent. An abdominal duplex ultrasound showed a patent SMA stent with normal velocities. The patient was placed on dual-antiplatelet therapy with aspirin and clopidogrel as well as a statin. He also began physical therapy to regain his leg strength. A follow-up mesenteric duplex ultrasound will be performed at 6 months to monitor the SMA stent patency. In addition, he will undergo a CT angiogram at 6 months and annually thereafter for endograft surveillance.

In 1999, Dake et al⁷  described the use of stent grafts to seal the proximal tear in Stanford type B aortic dissections. Thoracic endovascular aortic repair has gained popularity over open repair because of the resulting improved periprocedural morbidity and mortality. The primary goals of both endovascular and open surgery are to seal the primary entry tear, expand the true lumen, and reduce the false lumen pressure by inducing thrombosis.⁸  Complete false lumen thrombosis depressurizes the false lumen, resulting in a positive effect on aortic remodeling.⁹  This further reduces the risk of aortic adverse events.¹⁰ 

The coil embolization technique is used to enhance false lumen thrombosis and has several advantages. It poses a lower risk of stent graft injury from overexpanding a graft into a large false lumen. By conforming to the false lumen, it mitigates the risk of true lumen narrowing. It can also be performed in cases with challenging anatomy. No coil-related complications occurred in this case nor in other case reports from Rakestraw et al.¹¹ 

As experience in managing these complications evolves, several adjunctive techniques have been described. Spot stenting combined with false lumen endovascular occlusive repair is a technique that combines true and false lumen stent graft placement with coil embolization to promote false lumen thrombosis in select cases.¹²  More recently, a dissection-specific stent graft designed to prevent distal stent graft–induced tears has been reported with promising midterm outcomes.¹³ 

Persistent false lumen patency remains a common challenge in management of dissecting aortic aneurysms. New techniques continue to develop, one of which is coil embolization of the false lumen. This is a safe adjunct to induce false lumen thrombosis and reduce the risk of aortic events.