Endovascular Treatment of Acute Type B Dissection Complicating Aortic Coarctation

Abstract

Surgical treatment poses a high risk to patients with concomitant aortic coarctation and dissection, and an interventional approach could be an alternative. We describe the case of a 52-year-old man with a long history of untreated hypertension and aortic coarctation who emergently presented at our institution with an acute Stanford type B dissection. The patient's elevated serum creatinine level, perfusion deficit in the right lower limb, and hypertension did not respond to medical therapy, and he did not consent to surgery. By endovascular means, we used a self-expandable stent-graft to cover the entry point of the dissection; then, we deployed a balloon-expandable bare-metal stent to correct residual stenosis. To our knowledge, this is the first report of the endovascular treatment of aortic coarctation complicated by type B dissection.

Coarctation of the aorta is a narrowing of the aortic arch distal to the left subclavian artery.¹ Left untreated, the condition can lead to severe morbidity or be fatal.² Coarctation of the aorta can also occasionally be complicated by acute dissection, chiefly Stanford type A. Acute Stanford type B dissection, a rarer finding, has typically been treated with high-risk surgery.^3–5

Different transcatheter methods have been used to treat aortic coarctation^6–14; however, we found no report of the endovascular treatment of concurrent aortic coarctation and Stanford type B dissection. We report the case of a patient with chronic coarctation whose condition was complicated by acute type B dissection, and we describe our repair of both by endovascular means.

Case Report

In April 2011, a 52-year-old man emergently presented with the chief complaint of severe epigastric pain that radiated to his back and flanks. This pain was accompanied by nausea and right-lower-limb pain. The patient, who was hypertensive, had a 15-year history of severe aortic coarctation (Fig. 1A). He had been a candidate for surgical treatment, but he had refused for personal reasons. He was taking 80 mg of aspirin daily.

Fig. 1 Multidetector computed tomographic angiograms of the ascending aorta with intravenous contrast injection show A) Stanford type B dissection 2 years before the patient's emergent presentation and B) acute type B dissection at presentation.

Ao = ascending aorta; C = coarctation; F = false lumen; T = true lumen

Physical examination revealed a blood pressure of 195/114 mmHg and a grade 3/6 ejection-type systolic murmur, with its highest intensity at the left parasternal border. The pulse in the patient's distal left lower limb was detectable but weak, and no pulse was discernible in the right lower limb. Other physical findings were unremarkable.

Electrocardiography showed a nonspecific ST- or T-wave abnormality. Emergent transthoracic echocardiography showed a left ventricular ejection fraction of 0.55, left ventricular hypertrophy, an ascending aorta dilated to 43 mm, a bicuspid aortic valve with mild stenosis, mild-to-moderate mitral regurgitation, and aortic coarctation with a peak gradient of 40 mmHg.

Multidetector computed tomographic (CT) contrast angiography of the aorta and the iliac and femoral arteries showed a post-ductal aortic coarctation with a 6-mm stenotic segment. The diameters of the aortic root, sinotubular junction, and ascending aorta were 37, 32, and 50 mm, respectively. A Stanford type B aortic dissection just distal to the coarctation site extended to the right femoral artery (Fig. 1B). The celiac, superior mesenteric, renal, and inferior mesenteric arteries originated from the true lumen. The true lumina of the descending aorta, right common iliac artery, and right external iliac artery were completely compressed by the false lumen; however, the dissection did not extend to the left common iliac artery.

The patient's initial serum creatinine level of 1.19 mg/dL rose to 4.4 mg/dL after 3 days. He was given β-blocker and intravenous nitroprusside therapy for 3 days to control his blood pressure; however, these efforts were unsuccessful, and he became oliguric. The patient refused an offer of surgery. Because of his renal impairment, uncontrolled hypertension, and right-lower-limb pulse deficit, we decided to repair the coarctation by interventional means.

The procedures were performed in a hybrid suite with use of digital subtraction angiography and with the patient under general anesthesia. Intraoperative transesophageal echocardiography (TEE) was used to monitor the procedure.

Percutaneous retrograde access to the right radial artery was gained, and a 6F sheath was placed. Open retrograde cannulation of the left femoral artery was performed, and a 6F sheath was inserted over a 0.035-in soft-tipped hydrophilic guidewire. The post-coarctation pressure measured by this sheath was 135/60 mmHg. Heparin was used to achieve an activated clotting time of 250 to 300 seconds.

So that aortography could be performed, a 6F pigtail catheter was placed in the ascending aorta via the radial artery access. The pressure measured by this catheter was 170/90 mmHg; the coarctation gradient was 35 mmHg. Under TEE guidance, another 6F pigtail catheter was advanced via the left femoral access to the true lumen of the dissection in the thoracic aorta and was maneuvered to the coarctation site (Fig. 2A). The 0.035-in hydrophilic guidewire was then exchanged with a 0.035-in Lunderquist® extra-stiff wire (Cook Medical Inc.; Bloomington, Ind) via the pigtail of the left femoral access, and the 6F sheath was removed. Although we were not sure of the feasibility without predilation, a self-expandable Zenith® TX2® TAA Endovascular Stent with Pro-Form™ (Cook Medical) and its 20F sheath was advanced without predilation and was deployed just distal to the left subclavian artery to exclude the dissection entry point. A follow-up aortogram showed that a significant stenosis remained after the deployment of the stent-graft (Fig. 2B), and intraoperative TEE with color-flow Doppler revealed substantial flow from the true lumen to the false lumen (Fig. 3A). At this point, we decided to use a balloon-expandable, uncovered stent to repair the stenosis. An 8 × 3.9-cm CP Stent™ (NuMED, Inc.; Hopkinton, NY) was preloaded onto a 22-mm × 3.5-cm balloon (NuMED) by means of manual crimping, and we deployed it at the coarctation site inside the self-expandable stent (Fig. 2C).

Fig. 2 Digital subtraction aortograms show A) coarctation at the beginning of the procedure, B) remaining stenosis after the insertion (without predilation) of the self-expandable stent-graft just beyond the left subclavian artery, and C) deployment of the CP stent within the stent-graft at the coarctation site.

Ao = ascending aorta; C = coarctation site; CP = balloon-expandable Cheatham Platinum stent; F = false lumen; LSA = left subclavian artery; SG = self-expandable stent-graft; T = true lumen; TEE = transesophageal echocardiographic probe

Fig. 3 Transesophageal echocardiograms show A) remaining flow from the true lumen (T) to the false lumen (F) after insertion of the self-expandable stent-graft, and B) no significant flow after insertion of the balloon-expandable Cheatham Platinum stent into the stent-graft.

After the CP stent was deployed, an aortogram showed that the false lumen had collapsed and the true lumen had expanded, and there was mild residual angiographic evidence of the coarctation. The TEE images showed no visible flow from the true lumen to the false lumen (Fig. 3B). The pressure was 150/80 mmHg, and there was no significant pressure gradient across the coarctation site. Blood flow was unrestricted in the subclavian, renal, celiac, inferior and superior mesenteric, and left iliac arteries; however, flow to the right femoral artery was still restricted. We decided to perform a femorofemoral bypass to restore right femoral arterial flow with use of an EXXCEL™ Soft ePTFE Vascular Graft (MAQUET Cardiovascular, LLC; Wayne, NJ).

The patient was monitored for 24 hours in the intensive care unit for possible sequelae and for blood pressure control. His creatinine levels decreased to near normal, and his blood pressure remained under control. After 3 days, he was discharged from the hospital with instructions to take 80 mg of aspirin daily, 50 mg of atenolol twice daily, and 80 mg of valsartan twice daily.

Follow-up CT angiograms 1 and 7 months after the procedure showed a collapsed false lumen and no peri-stent leak (Figs. 4A and 4B). Blood flow to the patient's kidneys, other abdominal organs, and left femoral artery was normal (Fig. 4C), and the open femorofemoral bypass enabled perfusion of the right lower limb. The patient underwent follow-up for 1 year. His blood pressure was controlled appropriately, his creatinine levels were normal, and he was asymptomatic.

Fig. 4 Computed tomographic angiograms obtained A) 1 month and B) 7 months after the procedure. C) The 3-dimensional view at 1 month shows a collapsed false lumen, a patent graft and stent, and no peri-stent leak.

Ao = ascending aorta; CP = balloon-expandable Cheatham Platinum stent; F-F = femorofemoral bypass; LIA = left iliac artery; PA = pulmonary artery; R = renal artery; RIA = right iliac artery; SG = self-expandable stent-graft

Discussion

To our knowledge, there has been no similar report of aortic coarctation complicated by type B dissection with treatment by endovascular methods.

Acute, uncomplicated Stanford type B dissections are preferably treated by means of conservative medical therapy.¹ Indications for intervention in acute type B aortic dissection are rupture or signs of impending rupture, rapid diameter progression, end-organ malperfusion, persistent pain, and uncontrollable hypertension. Surgery for type B dissection yields a high rate of complications. Endovascular intervention has been proposed as an alternative to surgery, especially in patients with severe comorbidities; however, long-term data are unavailable. Closing the entry tear, usually with stent-grafts, can lead to thrombosis of the false lumen and expansion and remodeling of the true lumen. Furthermore, decreasing the pressure in the false lumen can restore perfusion in any compromised aortic branch vessel.¹

We initially treated our patient conservatively, but his impaired renal function, malperfused right lower limb, and uncontrolled hypertension were indications for intervention. Because he declined open surgical repair (which indeed would have been risky), we sought to repair the dissection and coarctation by endovascular means.

Ultrasonographic techniques, including intravascular ultrasonography (IVUS) and TEE, enable multiplanar access to the aorta. They yield valuable and incremental information for endovascular repair superior to that of angiography alone: identifying the true and false lumina, detecting slow flow in the false lumen after stent-graft implantation, showing incomplete stent-graft apposition,¹⁵ identifying suboptimal results such as peri-stent leaks or small re-entry tears, and aiding the selection of an appropriate stent-graft diameter.¹⁶ Because TEE might be superior to both angiography and IVUS in detecting endoleak after stent-graft implantation,¹⁵ the European Association of Echocardiography recommends the use of intraoperative TEE during and after endovascular intervention for type B aortic dissection.¹⁶ We followed this recommendation.

Among the various transcatheter methods for treating coarctation of the aorta, balloon angioplasty has been associated with dissection, recurrent coarctation, aneurysm formation,^6,7 and vascular injury.⁷ Balloon-expandable stents are a safe and effective alternative to surgery in many patients.⁸ Nitinol self-expandable aortic stents have also been used for this purpose.⁹ The covered balloon-expandable CP stent has been used in the treatment of aortic and recurrent coarctation with increasing frequency,6,10,12–14 and it is the preferred option in some patients.^6,14

Self-expandable stent-grafts have rarely been used in the treatment of aortic coarctation.^10,11 Kenny and colleagues¹¹ reported 3 cases in which self-expandable stents were deployed: one patient presented with mild recurrent coarctation and aneurysm formation, and 2 patients had acute hemoptysis secondary to aneurysm formation after previous coarctation repair. Pedra and associates¹⁰ used a self-expandable stent-graft to repair a coarctation accompanied by aneurysm at a repeat catheterization. Both sets of investigators reported that, although a self-expandable stent had insufficient radial force to open a tight aortic coarctation, it might be preferable to balloon-expandable stents when aneurysms have formed in the presence of aortopathy.^10,11

In our patient, we thought that a self-expandable stent-graft for repair of the dissection would be safer and more appropriate: it could avoid an additional local vascular trauma caused by the radial forces of a balloon, which in turn could have caused aortic rupture and dissection expansion. Consequently, we decided to cover the entry point of the dissection with a self-expandable stent-graft to enable expansion of the true lumen and thrombosis of the false lumen. We anticipated that this kind of stent could not exert radial force sufficient to open the coarctation, which would necessitate using balloon or balloon-expandable stents to repair the remaining coarctation. Therefore, we prepared for a hybrid operation. Because of the small aortic arch radius and aortic coarctation that might necessitate a balloon or balloon-expandable stent, it was important for us to maximize graft-to-wall opposition and ensure stent-graft conformability to the aortic arch; this is why we chose a Zenith TX2 Proform stent-graft that ensures conformability. Nevertheless, our chosen stent-graft might have been incorrect, because it did not expand sufficiently to repair the coarctation completely.

Our patient had a steep aortic arch, which rendered our landing zone suboptimal. In this case, leaving some insignificant residual stenosis (<50%) could potentially avoid unintended migration of the self-expandable stent and at the same time avoid coverage of the left subclavian and left common carotid ostia.

After covering the entry point of the dissection with a single self-expandable stent-graft, we realized that substantial stenosis remained across the coarctation and that there was still substantial flow from the true lumen to the false lumen. Balloon dilation of the coarctation was an option for the repair of the coarctation site, but our concerns about insufficient radial force—as well as the possibility of recoil and restenosis—prompted us to repair the remaining coarctation with a balloon-expandable bare-metal stent. The deployment of this stent inside the first stent reduced the angiographic stenosis and nearly discontinued the flow from the true lumen to the false lumen. It restored blood flow to the kidneys and other vital organs, although we had to perform a femorofemoral bypass to reperfuse the right lower limb.

Considering the high risk of surgery in patients with concomitant coarctation and dissection, endovascular intervention might prove to be an alternative. To maximize safety and success, we recommend performing a hybrid operation under intraoperative TEE guidance.

Acknowledgments

The authors thank Dr. Shapour Shirani for CT angiographic interpretation and gratefully acknowledge Mr. Salar Samimi and Dr. Kianoush Hosseini for their technical assistance.