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Original Articles: Adult Cardiac

Distal Landing Zone Open Fenestration Facilitates Endovascular Elephant Trunk Completion and False Lumen Thrombosis

Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio

Accepted for publication August 8, 2011.

^_* Address correspondence to Dr Roselli, Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, The Cleveland Clinic, 9500 Euclid Ave, J4-1, Cleveland, OH, 44195 (Email: roselle{at}ccf.org).

Presented at the Poster Session of the Forty-seventh Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 31–Feb 2, 2011.

	Abstract

Top Abstract Introduction Patients and Methods Results Comment References

 
Background: Controversy surrounds the endovascular treatment of chronic dissection because of inconsistent remodeling of the aorta. The purpose of this study was to assess efficacy and safety of a novel technique for repairing aneurysmal change associated with chronic descending aortic dissection.

Methods: From July 2007 to April 2011, 24 patients with descending aortic aneurysmal change, consequent to previously repaired ascending aortic dissection or medically treated descending dissection, underwent combined open first-stage elephant trunk (ET) insertion and fenestration of the descending aorta intimal flap. Second-stage ET endovascular completion was performed with the index operation in 4 patients and later in 20 patients (median, 62 days). Repair was elective in 14 patients and urgent in 10 patients. Concomitant procedures were aortic valve replacement in 3 patients and coronary revascularization in 3 patients, and 16 procedures were reoperations. Chart review and analysis of 3-dimensional computed tomography (CT) scans were performed. Imaging follow-up was complete in 89% of patients during a median of 18 months (interquartile range [IQR], 10 to 28 months).

Results: Technical success was achieved in all patients. Moderate reduction in aortic size occurred in most patients, with no retrograde false lumen flow. Late reintervention was required in 5 patients: endovascular for distal type I endoleak in 2 patients, type II endoleak in 1 patient, pseudoaneurysm of the abdominal aorta in 1 patient, and 1 open repair for aneurysm of the untreated distal segment in 1 patient. One patient died of pulmonary embolism on postoperative day 19 after 1-stage repair (4.0%) and 1 patient (4%) had a transient stroke, but there was no renal failure, respiratory failure, or permanent spinal cord injury. Median length of stay was 13 days (IQR, 8 to 16 days) after first-stage ET and 8 days (IQR, 5 to 12 days) after endovascular ET completion. One patient died during a mean of 23 ± 11 months of follow-up.

Conclusions: Open distal landing zone fenestration during first-stage ET facilitates endovascular completion for aneurysm associated with chronic distal dissection. Early results suggest that this technique is efficacious in eliminating retrograde false lumen filling and promoting aortic size reduction and is safe for patients.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment References

 
Most survivors of acute aortic dissection are left with residual disease and remain at late risk for aneurysmal degeneration [1]. Open repair is the recommended treatment for chronic distal aortic dissection with aneurysm, but thoracic endovascular aortic repair (TEVAR) is increasingly being used for this indication because of concerns about the morbidity of sizable open operations [2].

The objective during TEVAR in these patients is to cover the proximal entry tear and optimize true lumen flow thereby promoting false lumen thrombosis and reverse remodeling of the treated segment. TEVAR for chronic dissections is most successful when disease is limited to the descending thoracic aorta and both the proximal and distal landing zones are stable segments of aorta for fixation and sealing [3]. However many patients with chronic dissection have extensive aneurysm with a pattern of disease in which neither of the landing zones is ideal. Open arch repair with an elephant trunk (ET) procedure has been shown to provide a stable proximal landing zone for the placement of a stent-graft [4, 5]. When the distal landing zone has residual dissection, however, the ability to predict thromboexclusion of the treated segment is unreliable because of persistent retrograde filling and pressurization of the false lumen (Fig 1) [3, 6–10].

View larger version (30K): [in this window] [in a new window]   Fig 1. Endovascular controversy in the treatment of chronic dissection with aneurysm: thromboexclusion of the false lumen is unpredictable because of retrograde filling and continued pressurization (arrows).

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment References

 
Patient Characteristics
From July 2007 to April 2011, 24 patients underwent both stages of the described novel technique. Two additional patients not yet included in the analysis have successfully undergone the first-stage operation and are awaiting the second-stage TEVAR operation. The mean patient age was 57 ± 10.7 years. All patients were survivors of either surgical proximal repair after acute extended type A dissection (n = 14), or medical therapy for acute type B dissection with proximal extension (n = 10) and had experienced aneurysmal degeneration. One patient had undergone previous coarctation repair, and 2 patients had Kommerell's diverticulum associated with an aberrant right subclavian artery that was dissected. Median time from acute dissection to first-stage repair was 22 months (IQR, 11 to 46 months). Mean maximum aortic diameter was 5.9 ± 1.0 cm and the largest segment consistently involved the proximal descending aorta, as is most typical of patients with aneurysmal degeneration of chronic dissection [11]. Data was prospectively collected into the Cardiovascular Information Registry, which is approved by the Institutional Review Board of the Cleveland Clinic, and the need for informed consent was waived for this study.

Operative Technique
First stage
All patients underwent first-stage repair through a median sternotomy; this was a redo median sternotomy in 16 patients. The right axillary artery was used for arterial inflow during cardiopulmonary bypass in all patients, with construction of a conduit side graft as previously described [12]. All patients underwent hypothermic circulatory arrest with selective antegrade brain perfusion. Arch reconstruction was performed first during a period of deep circulatory arrest for a mean of 18.5 ± 6 minutes. This was followed by ET insertion and open fenestration of the distal descending aortic landing zone performed during the period of selective antegrade brain perfusion (mean of 55 ± 10 minutes) (Fig 2). The descending aorta was exposed with assistance of a fixed retractor, and the aortotomy and length of septum excised was typically about 5 to 6 cm (Fig 3 ). After establishing full flow, the proximal aortic reconstruction was completed. Four patients also underwent aortic valve replacement, and 3 patients had coronary artery bypass grafting simultaneously.

View larger version (41K): [in this window] [in a new window]   Fig 2. Distal landing zone open fenestration procedure. (A) Heart retracted cephalad to expose distal descending aorta through posterior pericardium or left pleural space. (B) Dissection flap excised through anterior longitudinal aortotomy. Intraoperative view of chronic dissection flap through aortotomy before (blue arrow in B) and after (blue arrow in C) open fenestration.

View larger version (40K): [in this window] [in a new window]   Fig 3. Chronic aorta with aneurysm after first-stage repair. The arrow in the illustration in panel (A) marks planned distal landing zone for second-stage endovascular completion. Axial computed tomographic scan of modified distal landing zone preoperatively (B) and postoperatively (C). Note the radiopaque metallic clip marking the modified distal landing zone.

View larger version (107K): [in this window] [in a new window]   Fig 4. (A) Illustration and (B) volume-rendered computed tomography scan demonstrating completed 2-stage repair with stent graft spanning from elephant trunk to modified distal landing zone with complete circumferential seal to adventitia and exclusion of retrograde false lumen filling.

Follow-Up and Imaging
Postoperative computed tomography (CT) was performed using a standardized 3-phase protocol after the stent graft was in place, including a noncontrast phase through the treated segment and intravenous contrast scans through the chest, abdomen, and pelvis timed for the arterial and delayed venous phases. All of these images were analyzed using 3-dimensional reconstruction software (Aquarius, TeraRecon, San Mateo, CA) to assess for patency of the repair, device integrity, endoleaks, and morphologic characteristics of the aneurysm.

Clinical and CT imaging assessment was performed before discharge, within the first 6 months, 12 months postoperatively, and annually thereafter. Mortality data were available for all patients, and eligible patients were compliant with 89% of their scheduled imaging follow-ups. Patients who underwent concomitant valve surgery or had left ventricular dysfunction also underwent echocardiography during follow-up.

Survival was confirmed by query of the Social Security Death Index at a median follow-up of 25 months (IQR, 13 to 31)

Outcome Definitions and Statistics
Technical success was defined by prosthesis implantation with patency of all intended arch and visceral branches, no angiographic evidence of type I or type III endoleak (for the endovascular stage only), and survival at 24 hours. Stroke included neurologic deficit lasting greater than 24 hours confirmed by cross-sectional imaging of the brain or documentation by a neurologist. Spinal cord injury was defined as paraplegia or paraparesis, and was confirmed by cross-sectional imaging of the spinal cord or documentation by a neurologist. Renal failure was defined as the need for hemodialysis. Respiratory failure included the need for reintubation or tracheostomy. Bleeding was defined as the need for reoperation.

At follow-up, false lumen thrombosis was confirmed as being complete by CT imaging performed in both the arterial and venous (low flow) phases of the study.

Standard descriptive statistical analyses were used. Continuous variables are presented as the mean ± standard deviation or median with the IQR (due to the small sample size), and categorical variables are presented as percentages. Survival was assessed by the Kaplan-Meier method.

	Results

Top Abstract Introduction Patients and Methods Results Comment References

 
Early Outcomes
Technical success was achieved in all patients during each operation. In-hospital mortality and postoperative complications are presented in Table 1. The only hospital death occurred on postoperative day 19 as a result of massive pulmonary embolus in a woman with a body mass index of 45 kg/m² who presented with rapid growth of a degenerative distal arch aneurysm 6 months after surviving acute type A dissection repair with a supracoronary graft. She was also the only patient with spinal cord injury that occurred in a delayed fashion, but she had complete recovery of strength in 1 leg and progressive recovery in the other before dying of the pulmonary embolism.

View larger version (15K): [in this window] [in a new window]   Fig 5. Estimated survival at median follow-up of 24 months.

Two patients required placement of an extension graft for distal type I endoleak. One was described previously in the section Midterm Survival, and the other patient required reintervention 20 months postoperatively. One patient required endovascular coil embolization of the native left subclavian artery for a type II endoleak, which was performed through a percutaneous left brachial puncture 2 months postoperatively.

Reverse Remodeling
Imaging follow-up was excellent in these patients. There were 11 total endoleaks: 2 distal type I, both of which underwent successful endovascular repair and 9 type II: 1 resolved with intervention, 4 without, and 4 persisted as of this writing with no aortic growth and are being followed expectantly. There have been no type III endoleaks.

Of the 23 survivors with imaging follow-up, 16 demonstrated shrinkage of the aneurysm sac, 5 have been stable in size, and 2 grew. Both patients with growth had late distal type I endoleaks that were treated, and none has ruptured.

	Comment

Top Abstract Introduction Patients and Methods Results Comment References

 
Principal Findings
The novel technique described here is a safe and effective alternative for treating the complex population of patients with extensive chronic aortic dissection with aneurysm. This hybrid approach not only allows for complete thoracic aortic repair within a relatively short time frame but also reliably excludes flow and pressurization of the false lumen in the treated segment of aorta. With close imaging surveillance, there have been no aortic-related deaths at intermediate-term follow-up.

Operative Technique
The 2-stage ET repair approach has been favored for patients with extensive thoracic aortic disease with reasonable results [14–18]. One of the biggest criticisms of this approach is the inherent risk of rupture when completion repair is delayed between stages. In fact, one fifth to one half of patients do not return for the second stage either because complications from the first repair have rendered them unsuitable for further surgery or the patients themselves have chosen not to undergo an arguably bigger second operation. For those who do complete the 2-stage repair, the combined mortality of the 2 operations ranges from 8% to 20%.

Kouchoukos and colleagues [19] have championed a single-stage strategy for dealing with this complex subset of patients by approaching both the proximal and distal thoracic aorta through a clamshell incision. The population of patients in that experience is very similar to the population described here. The results of this approach are excellent and have been reported several times, with the latest mortality in the series of 95 patients at 8.4%. Although this technique eliminates the delay between stages and therefore the risk of interval rupture, it is a morbid procedure, with 17% of patients requiring tracheostomy and 8% requiring hemodialysis perioperatively.

Although exposure and management of the distal descending thoracic aorta through a sternotomy is not a simple task, by limiting this portion of the operation to the anterior wall only it is safe and feasible. This technique does not include the technical difficulties and the risk of bleeding associated with a complete open anastomosis involving the posterior aortic wall and intercostal branch handling. Nonetheless we did have 2 intraoperative aortic ruptures and a distal pseudoaneurysm probably related to the altered flow dynamics and additional manipulation of a chronically dissected aorta. When addressing the dissection flap, resection is minimized and longitudinal incision of the flap preferred. Thrombus material within the false lumen is left alone if densely adherent.

It is our belief that much of the morbidity from extensive aortic repair using conventional 1- or 2-stage open techniques is related to the distal aortic reconstruction. Others have recently demonstrated excellent outcomes for proximal aortic repair including the entire aortic arch using various methods for brain protection with circulatory arrest [20, 21]. By completing these repairs endovascularly, it is expected that the majority of risk is incurred during the first stage and therefore the overall risk of total thoracic aortic repair may be improved [4, 5]. The exception to this is the risk of spinal cord injury, which is not eliminated by the endovascular approach but is most closely associated with the extent of aorta repaired [22]. Recent animal studies conducted by Zoli and associates [23], however, support the staged approach to aortic repair as a means of reducing this dreaded complication. The 1 patient in this series who experienced paraparesis had undergone a single-stage repair, and that approach has been abandoned since then unless absolutely necessary (ie, rupture).

All patients offered the hybrid 2-stage approach as described here have returned for the completion repair at the appropriate time. Although they understand that the endovascular descending aortic repair and potential for spinal cord injury are serious issues, the prospect of avoiding another large incision has encouraged them to return for completion.

Patient Selection
The periprocedural benefits of reduced morbidity with TEVAR over open repair have been demonstrated many times for degenerative aneurysms, but the long-term durability of endovascular repair in patients with chronic dissection has come into question [2]. The main controversy relates to the inconsistency with which the aneurysmal false lumen heals in patients treated with this technique. It is quite commonly the case that persistent retrograde filling of the false lumen from downstream reentry tears and fenestrations pressurizes the aneurysmal segment and the risk for growth or rupture persists (Fig 1). Furthermore the chronic intimal flap is thickened and fibrotic and will not expand to the adjacent adventitial layer of the false lumen. With the approach described here, the intimal flap is resected over the entire length of the distal landing zone (approximately 6 cm) so that the stent-graft device can seal to adventitia circumferentially, thereby eliminating retrograde filling of the false lumen in the treated segment (Fig 4).

The intended goal was achieved in all patients, but 2 required late reintervention for type I endoleaks occurring within the distal landing zone. In both of these patients, the device was not extended far enough across the entire fenestrated segment. In 1 case this occurred because the device was placed using a portable C-arm because rupture had occurred intraoperatively during the first-phase operation. In the other case, the segment of aorta that was modified by fenestration was also reduced in size to accommodate the stent-graft device by performing an aortoplasty of the adventitia in addition to the open fenestration. The same adventitial aortoplasty procedure was performed in a second patient who had an adequate initial result but later required reoperation for aneurysmal degeneration of the abdominal aorta. For TEVAR in a patient with a degenerative aneurysm, it is recommended that the landing zone be at least 2 cm in length in a relatively normal segment of aorta. Although the newly fenestrated distal landing zone is not completely normal, we are now careful to select patients for this procedure in whom the overall diameter of the distal landing zone to be fenestrated is less than 4 cm to avoid the risk of intermediate-term degeneration.

Although the need for later reintervention in these patients was not trivial, it is well known that patients with extensive chronic aortic dissection have a persistent lifetime risk for reintervention. The rate of reintervention in the single-stage clamshell series was 7.4% and included reoperations on the treated and untreated segments. The occurrence of endoleaks is inherent to endovascular procedures and is not seen with open procedures, but disease progression can occur regardless of repair technique. Therefore, these patients should undergo lifetime regularly scheduled surveillance imaging of their aortas, especially the residually dissected segments.

Conclusions
Hybrid 2-stage repair—involving ET and open distal landing zone fenestration followed by endovascular completion—for aneurysm associated with extensive chronic distal dissection is safe and effective for patients. Intermediate term follow-up demonstrates that it eliminates retrograde false lumen filling and promotes aortic size reduction. This technique is recommended for patients with extensive chronic dissection and aneurysmal degeneration involving the thoracic aorta.

	References

Top Abstract Introduction Patients and Methods Results Comment References

 

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This article has been cited by other articles:

				N. T. Kouchoukos The Elephant Trunk Procedure for Chronic Aortic Dissection Ann. Thorac. Surg., November 1, 2012; 94(5): 1782 - 1782. [Full Text] [PDF]

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				S. Trimarchi and C. De Vincentiis Invited Commentary Ann. Thorac. Surg., December 1, 2011; 92(6): 2084 - 2084. [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Eric E. Roselli Edgardo Sepulveda Edward Nowicki Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Roselli, E. E. Articles by Nowicki, E. Search for Related Content PubMed PubMed Citation Articles by Roselli, E. E. Articles by Nowicki, E. Related Collections Great vessels Related Article