Promoting a Hybrid Technique for Repair of Thoracic Aortic Aneurysms in the Complicated Patient

Hybrid Repair of Aortic Arch Aneurysm

Castigliano M Bhamidipati DO MSc, James N Irvine BS, Klaus DHagspiel MD†,

Alan H Matsumoto MD†, Megan C Tracci MD JD, John A Kern MD

†Department of Radiology & Medical Imaging

Department of Surgery

University of Virginia School of Medicine, Charlottesville, VA

Corresponding Author,

John A Kern, MD

Associate Professor of Surgery

Division of Thoracic and Cardiovascular Surgery

University of Virginia Health System

P.O. Box 800679

Charlottesville, VA 22908

Office: 434-982-4301

Fax: 434-243-5781

Email:

ABSTRACT

Hybrid repair of thoracic aortic aneurysm has been used with increasing frequency over the past decade as indications for endovascular therapy have continued to expand. Hybrid techniques may avoid and limit the morbidity and mortality associated with sternotomy or thoracotomy, mechanical circulatory support, and hypothermic arrest. We present the case of extensive aortic aneurysmal disease initially needing open ascending aortic andsubsequentthoracoabdominal repair. However, due to continued enlargement of the aortic arch, ultimatelyhybrid extra-thoracic, extra-anatomic complete aortic arch debranchingandtranscatheter endografting was pursuedwith favorable mid-term results.

CASE SUMMARY

In late 1998,a 68-year-old non-smoker active female with treated hypertension and hypercholesterolemia, and no prior vascular disease,was managed with empiric intravenous antibiotics and aggressive beta-adrenergic blockade foran occult locallyinflammatory abdominalaortitis. Serial erythrocyte sedimentation rates remained above 90mm/hour, and imaging studies revealed a concomitant aortic dissection distal to the inferior mesenteric artery. Repeatedimaginganalyses also revealed anincidental ascending aortic aneurysm (<4.0cm). The aortitis quiesed andthe distaldissection remained stable with medical optimization. Between 1998 and 2000 theascending aortic aneurysm dilatedto 5.2cm, leading to anuncomplicated open aneurysm repair with a 30mm Gelweave™graft (Terumo Cardiovascular Systems Corporation, Ann Arbor, MI). Re-exploration for presumed bleeding did not reveal any surgical source. Seven years later while traveling out of state, the patient presented to an outside emergency department with an acute Type III aortic dissection involving the entire descending aorta. Once clinically feasible the patient was transferred to our facility, where studiesrevealed extension of thedissection into bilateral renal arteries with malperfusion. Percutaneous femoral access revascularization by transcatheterexclusion of both false renal lumens,and aggressive medical therapy for the complicated Type III descending thoracic aorta (DTA) dissection werestabilizing. Within 6 months, despite aggressive betablockade, the patient developed worsening discomfort with progressive aneurysmal dilatation of her distal DTA to 6.0cm. An uneventful left thoracotomy for Crawford Type III thoracoabdominal aneurysm repair, with 38mm x 60mm Gelweave™ graftwas completed. Again re-exploration for presumed bleeding was warranted, yet did not yield a surgical source.

During follow-up surveillance, a known 4.0cm mid-distal aortic arch (Zone 4)aneurysmwith dissection was confirmed angiographically to have enlarged to 6.0cm (Figure 1A). Given the necessity to treat thissignificant arch pathology, in the face of prior extensive surgical repair of the ascending and distal DTA, with previous sternotomy and thoracotomy each requiring separate re-explorations, a hybrid repair was practical. Fortuitously, the aforementioned ascending and descending graftswere putative well-defined landing zones. Taken together,hybrid technique that included, 1)extra-thoracic,extra-anatomic complete debranching of thearch, and 2)transcatheter thoracic endografting of the aortic archwasideal.

There were several important considerationsduring the development and implementation of the surgical plan. Significantly, prior imaging confirmed a complete Circle of Willis, with dominant right vertebral and patent left subclavian arteries. Thus to facilitate an extra-thoracic complete aortic debranching, an extra-anatomic in-flow conduit was fundamental. Debranching of the aortic arch was facilitated via a 10mm ringed Gore-Tex® (W. L. Gore & Associates Inc., Flagstaff, AZ) polytetrafluoroethylene graft from the right femoral to axillary artery (Figure 1B). An 8mm polytetrafluoroethyleneGore-Tex® graft from the right subclavian to the right carotid artery, and then an additional 8mm jump graft from here[right carotid artery] to the left carotid artery were fashioned(Figure 1C), after which bilateral carotid arteries were ligated.

On postoperative day 2, following an intact neurological examination, all four limbs were prepped for transcatheter access. The right arm and groin facilitated locator pigtailcatheter placement(s), while the left groin enabledaccess for device deployment. Multiple endograft devices were required due to aortomegaly and tortuous DTA anatomy. Specifically, a 34mm x 20cm Gore® TAG®endoprosthesis (W. L. Gore & Associates Inc., Flagstaff, AZ) was landed proximally into the previously placed ascending aortic graft. This was followed by telescoped 38mm x 20cm Zenith® TX2® (Cook Medical Inc., Bloomington, IN) and 42mm x 16cm Zenith® TX2® in tandem, such that the proximalstent deployed into the Gore® TAG®endoprosthesiswith satisfactoryoverlap, and distally landedinto the thoracoabdominal repair graft (Figure 1D). Additionally, two Amplatzer® devices (St. Jude Medical, Inc., St. Paul, MN) at each of the bilateral subclavianartery takeoffs,were deployed via ipsilateral arms, to avoid potential endoleaks. During the second right subclavian Amplatzer® device delivery, a small subclavian dissection was noted extending into the right vertebral artery, and so the origin of the right vertebral artery was stented.

No cerebrospinal spinal fluid drains were placed for the above endografting, and despite transient postoperative right upper extremity neuropraxia, imaging studiesdid notidentifyany lesions. Ultimatelythe patient was optimized for acute rehabilitation. Evanescent fever with rigors was treated conservatively, and 6-month follow-up had no evidence of infection. Notably, imaging studies confirmed that the arch aneurysm had remodeled, and the patient made full recovery returning to baseline function. Almost three years later she continues to live independently at home,and has had no further sequelae.

COMMENT

We present complex aortopathy with aortomegaly in an active elderly female with extensive aneurysmal disease presenting with recurrent dilatations andaortic dissection. Extra-anatomic repair in ascending and aortic arch dissection has been described in the past.1-3 In aortic arch aneurysms, occlusion of the supra-aortic branches and arterial bypass is often required before endovascular stent deployment. Our choice of aortic debranching, with complete extra-thoracic, extra-anatomic reconstruction of the aortic arch, permitted anexpanded landing zone for endograft support and avoided redo sternotomy. We selected a combinationof endograft devices since, 1)in our opinion the Gore® TAG® endoprosthesis is more compliantwith better aortic arch trackingand shorter nose cone,and 2) at the time of endograftingaortictortuosity and angulation requireda larger device distally.

Another important deliberation was that the patient had undergone previous sternotomy and thoracotomy,thatboth required second look operations for supposed bleeding. Notably, the tissue was found to be friable and progressively degenerative at each surgical exposure. Given that, 1)from T9-T10 of the DTA through the abdominal aorta was native, 2) dependent on series the 10-year primary patency for axillofemoral bypass is between 60-80%, and 3) tissue quality was very poor for open repair, our described hybrid procedure was preferred. A bilateral femoral to axillary artery bypass could have been another surgical option, however, given the much smaller left vertebral artery and the potential for future lower extremity revascularization, a bilateral approach was not pursued.

Retrospective reflection of this case raised concerns for several connective tissue diseases, aortitis, aortic dissection, metachronous aortic aneurysm, and/or various rheumatologic diagnoses. To this end, the primary provider(s) continue to garner input from appropriate expertise for comprehensive management. A closer temporal review of post-processed high-resolution images revealed several smaller aneurysms and dissections along the celiac, hepatic, gastric, and superior mesenteric arteries. The presence of innumerable asymptomatic stable mesenteric dissections associated with local aneurysms was vexing, and raisedconcerns for segmental mediolytic arteritis (SMA). First discussed in 1976, SMA is a rare vasculopathy of unknown etiology characterized by myolytic dysplasia of the arterial medial layer, with resultant susceptibility for dissection, hemorrhage, and ischemia.4 SMA is initiated by the arterial vascular smooth-muscle cell (VSMC) cytoplasmic contents that transform into dilated vacuoles and store fluid. These vacuoles rupture, causingVSMC disruption leading to mediolysis,which is also associated by fibrin deposition and hemorrhage at the adventitio-medial junction and aortic medial layer. Inflammation is limited to the abluminal surface, and transmural mediolysis leads to arterial wall defects bridged by a serofibrinous deposition. Separately, Verhoeff-Van Gieson stainingof intraoperatively obtained arterial sections was noted to have elastic lamina reduplication. Hence, with an extensive disease burden, seronegative workup, and a vasculitis-like presentation, the overwhelming circumstantial clinical evidence supports the probability of SMA in our patient.

This case illustrates the feasibility and utility of total extra-thoracic,extra-anatomic debranching of the aortic arch to facilitate endograft deployment as an alternative to open repair of arch aneurysms in select patients.5 Patients with large thoracic aortic aneurysms are more likely to die from rupture or complications of aneurysm than from any other cause with 21% 5-year survival. TEVAR continues to evolve with improvements in devices and techniques, especially hybrid approaches that accommodate landing zones along the aortic arch. To the best of our knowledge, no large, long-term observations analyzing hybrid technique for thoracic aortic aneurysms have been reported. Numerous case reports confirm short- and mid-term success, with morbidity and mortality comparable to conventional open repair. Our hybrid approach in select patients where open repair can be prohibitive providesa novel treatment option.

FIGURE LEGEND

Figure 1A. Axial image shows true lumen of acute mid-distal aortic arch (Zone 4) dissection (black asterisks).

Figure 1B. Extra-anatomic right common femoral to axillary artery bypass (red solid arrows) establishes in-flow conduit.

Figure 1C. Right subclavian-carotid-carotid bypass shows cerebral flow conduits (fenestrated red arrows) and aortic arch debranching.

Figure 1D. Thoracic endografting from sino-tubular junction through diaphragm with expanded proximal and distal landing zones (solid white arrows).

REFERENCES

1.Chiesa R, Tshomba Y, Melissano G, et al. Hybrid approach to thoracoabdominal aortic aneurysms in patients with prior aortic surgery. J Vasc Surg. Jun 2007;45(6):1128-1135.

2.Bockler D, Kotelis D, Geisbusch P, et al. Hybrid procedures for thoracoabdominal aortic aneurysms and chronic aortic dissections - a single center experience in 28 patients. J Vasc Surg. Apr 2008;47(4):724-732.

3.Dias Perera A, Willis AK, Fernandez JD, Garrett HE, Jr., Wolf BA. Staged total exclusion of the aorta for chronic type B aortic dissection. J Vasc Surg. Nov 2010;52(5):1339-1342.

4.Slavin RE, Gonzalez-Vitale JC. Segmental mediolytic arteritis: a clinical pathologic study. Lab Invest. Jul 1976;35(1):23-29.

5.Kpodonu J, Peterson MD, Aquiar-Lucas L, Rodriguez-Lopez JA, Diethrich EB. An extra anatomic, close chest approach to manage an aortic arch aneurysm in an 88-year-old woman. Ann Thorac Surg. Sep 2007;84(3):1045-1047.