Short and Longer Term Results of Hybrid Repair of Arch and Proximal Descending Thoracic

Short and longer term results of hybrid repair of arch and proximal descending thoracic aorticpathology: a bench mark for new technologies.

Purpose:

To evaluate the short and longer term outcomes of hybrid repair of the arch and proximal descending aorta in a single tertiary centre for aortic disease.

Methods:

Retrospective analysis of a prospective database identified55 patients undergoing hybrid repair of thoracic aortic pathology with involvement of the arch between January 2005 and May 2015.Demographic and procedural characteristics werecollected and both short and longer term survival and re-interventions analysed.

Results:

65.5% of patients were male with a median age of 67 years. 12.7% of procedures were performed as an emergency. 27.3% of patients required aortic de-branching to facilitate endograft placement in zone 0, 34.5% in zone 1 and 38.2% in zone 2. Primary technical success was achieved in 92.7% of cases. 30-day mortality was 2.1% and 14.3% in elective and emergency cases respectively, and 3.6% overall. The rate of procedural stroke was 12.5% in elective cases, 28.6% in emergency cases and 14.5% overall. Spinal cord ischaemia was reported in 5.7% of patients. Mean follow-up was 74.6 months. Overall cumulative survival was 70% at 1 year, 68% at 2 years and 57% at 5 years. Re-intervention to the proximal landing zone for type 1a endoleak was required in 5.7% of cases. The overall rate of aortic re-intervention was 18% at 1 year, 21% at 2 years and 36% at 5 years. Overall extra-anatomical graft patency was 98.7%.

Conclusions:

Hybrid repair of aortic arch and proximal descending thoracic aorta is technically feasible with an acceptable short term mortality. There is a low rate of proximal landing zone re-intervention when hybrid techniques are used to create an adequate proximal landing zone. Extra-anatomical bypass grafts have a good long term patency rate.Ongoingdisease progression means that further distal aortic re-intervention is often necessary in those with extensive disease.

MeSH KEYWORDS

Aortic arch, descending thoracic aorta, endograft, endovascular treatment/therapy, hybrid repair, proximal seal, reporting standards, stent graft, surgery

Introduction

Traditional open approaches to the management of disease of the aortic arch and proximal descending thoracic aortaare associated with significant morbidity and mortality, particularly in high-risk patientsas the need for circulatory arrest is not well tolerated in this group.1, 2, 3, 4, 5Endovascular treatment of thoracic aortic pathologies is a well-established surgical technique with superior short term outcomes when compared with open approaches, but is limited by the need for an adequate seal and fixation.6, 7, 8, 9First described in 199810the arch hybrid techniqueutilisesthoracic aortic stent grafting together with supra-aortic de-branching to extend the proximal landing zone. This technique facilitateslong term fixation and adequate seal of the endograft,and is a viable alternative technique to aid in the treatment of complex pathologies that extend across the arch of the aorta.11, 12, 13, 14

The evolution of endovascular technology has meant that total endovascular approaches to the treatment of the aortic arch are now available,however this technology is still in its’ infancy and requiresfurther evaluation particularly with regards to stroke rates and long-term outcomes, feasibility and durability.15, 16, 17Reporting of the short and long-term results of hybrid treatment for disease involving the aortic arch is necessary for comparison with current and future treatment options and techniques.

We have previously reported on the short-term outcomes of this technique18 in our institution.The aim of this study was to report our experience with the management of complex disease of the aortic arch and descending thoracic aortic through a hybrid approach, and to assess outcomes and long-term results in this cohort.

Methods:

Study Design:

We performed a retrospective review of a prospectively collected departmental databasefrom a tertiary referral centre for complex aortic and thoracoabdominal aortic disease. Consecutive patients identified as undergoing hybrid arch repair (HAR) for thoracic aortic pathology with involvement of the arch between January 2005 and May 2015 were identified and included in the study. Those undergoing open repair, operations combined with other major procedures and those with a scallop or single branched device for the left subclavian artery (LSA) were excluded. Data was collected for patient demographics, significant co-morbidities, aortic pathology and indication for intervention, procedural characteristics, short-term outcomes, and long-term follow-up based upon suggested minimum pragmatic reporting standards for TEVAR.19

Emergency and elective cases were included in the study. Patients operated on for aortic arch aneurysms, thoracic aortic aneurysms (TAA), thoracoabdominal aortic aneurysms (TAAA, type I and II), aortic dissection (acute and chronic, Type A and B) and acute aortic syndrome (intra-mural haematoma (IMH) and penetrating aortic ulcer (PAU)) were all included in the study. Patients with underlying connective tissue disorders, or those who had previously undergone aortic intervention including root replacement, coarctation repair and additional interventions to the distal aorta either before, or after their HAR were also included in the study.

Patient Population:

Fifty-five patients with available medical records were identified from the database search. Pre-operative patient characteristics and procedural information are described in Table 1. The majority (36/55, 65.5%) of patients were male, with a median age of 67 years (range 38-88). The overwhelming majority (48/55, 87.2%) were American Society of Anesthesiologists (ASA) grade 3 or 4 at time of surgery. 18/55 (25.5%) of patients had had previous aortic surgery; the majority either for Type A aortic dissection or repair of coarctation of the aorta in the past. A small number (3/55 5.5%) had a history of known connective tissue disorders, and all had had previous aortic surgery. 28 (51.0%) of patients were treated for symptomatic disease, and 7 (12.7%) as an emergency with the procedure performed within 24hrs of onset of symptoms. The majority of patients had their procedure performed for aneurysmal disease (40/55 72.7%). 10 (18.2%) had HAR performed for acute Type B aortic dissection, and 1 patient deemed too high risk for open surgery had the procedure performed for an acute Type A dissection. Four patients had HAR performed for other pathology; acute aortic syndrome with a penetrating aortic ulcer/intra-mural haematoma in two cases, a case of an aberrant right subclavian artery (RSA) aneurysm and a further case of a LSA aneurysm. In those patients with aneurysmal disease 15 (37.5%) were as a result of aneurysmal dilatation of the false lumen in chronic Type B aortic dissection, and 5 (12.5%) were as a result of aneurysmal dilatation at either the proximal or distal anastomosis in a previous coarctation repair.

Details of the supra-aortic de-branching procedures performed by landing zone are summarised in Table 2. Complete aortic de-branching to facilitate a proximal landing zone within zone 0 was performed in 15 (27.3%) patients, of which two patients had stent grafts inserted with either a fenestration or scallop for the innominate artery (IA). Partial de-branching was performed in 19 (34.5%) patients for zone 1 landing zones, and 20 (38.2%) for zone 2 landing zones. Overall 42 (76.4%) of patients also had re-vascularisation of the LSA performed through either a LCCA-LSA bypass or LSA transposition.

32/55 (58.2%) of cases were performed as single stage procedures, with both aortic de-branching and TEVAR performed within the same operative period, whilst the remaining 23 (41.8%) cases were performed as staged procedures; aortic de-branching being performed prior to stent insertion (median 18 days, range 2-259). A single patient died following an initial uncomplicated de-branching procedure (RCCA-LCCA bypass) prior to TEVAR as a result of spontaneous aneurysm rupture 6 days post-operatively. A mean of 2.52 (range 1-9) aortic stents were placed in each patient, depending on pathology and length of aortic coverage required for primary technical success. 40/55 (72.7%) of patients had a spinal drain placed for their procedure.

Surgical Techniques:

The technique may be performed as a single concomitant procedure, or as a staged repair with de-branching occurring prior to the endograft being placed. In deciding which approach to adopt it is important to take into account patient, pathological and technical factors; concomitant repair being mandatory in emergency cases, or those large aneurysms with a high rupture risk. Wherever feasible a staged approach is preferred with de-branching occurring prior to the endograft being placed which we believe reduces peri-operative risk after de-branching, in addition to reducing spinal cord ischaemia (SCI) risk when there is extensive coverage of the thoracic aorta.

For extra-anatomical reconstruction we routinely use a left carotid-subclavianbypass graft performed through a left supraclavicular incision for those patients requiringstent graft placement in zone 2,together with ligation or embolisation of the left subclavian artery (LSA)proximal to the vertebral artery origin. A minority of patients had a LSA transposition performed through the same approach as an alternative. For patients requiring stent graft placement in zone 1we usually perform a carotid-carotid bypass graft tunneled anteriorly, or more recently via a retro-oesophageal approach. A separate carotid subclavian bypass or an extension of the carotid-carotid bypass to the subclavian vessel is also used in these patients, and the proximal left carotid artery is also ligated or embolised. For those patients requiring placement of the stent graft zone 0 we perform neo-innominate reconstruction through a median sternotomy, utilising a side-biting clamp on the aorta. A variety of graft configurations can be used in this procedure; commonly a 10mm Dacron graft from the ascending aorta to innominate artery,together with an 8mm graft from this to the left common carotid artery and a left carotid subclavian bypass in the neck. Examples of Zone 0, 1 and 2 de-branching procedures are shown in Figure 1.

Placement of the endograft is performed via thecommon femoral artery (CFA), or iliac conduit where there are access issues due to diseased or small external iliac vessels. Contralateral CFA access isusually used for imaging catheter introduction. All patients are heparinized, and after detailed imaging the stent is deployed. In describing the procedural characteristics, the Ishimaru classification was used to categorise the proximal landing zone of the stent graft.20For stent deployment in zone 2 we use drug induced hypotension to reduce stent graft mal-deployment, and for deployment in zone 0 and 1 overdrive cardiac pacing is employed to ensure accurate graft placement. Selective spinal cord protection with pre-operative spinal drain insertion is used dependent on patient factors e.g. concurrent anti-coagulation therapy, presence of previous aortic surgery and the intended length of aorta to be covered by the endograft.

Primary technical success was defined as completed supra-aortic reconstruction, together with satisfactory deployment of the stent graft with no type 1a/1b or 3 endoleak, retrograde type A dissection, stent collapse or deformation, stent migration during deployment or conversion to an open procedure.

Short-term outcome data was collected to include primary measures of technical success together with 30-day and in-hospital mortality. Data for in-hospital morbidity including stroke, spinal cord ischaemia and surgical re-intervention was also collected as per suggested reporting criteria for TEVAR.19

Our standard follow-up protocol consists of computed tomography angiography (CTA) imaging of the whole aorta and supra-aortic vessels at four weeks post-operatively, with annual CT imaging thereafter unless clinically indicated. Annual duplex ultrasound surveillance of the extra-anatomical bypass grafts is also performed. In addition,patientsarereviewed on a regular basis within the outpatient setting either at our unit, or at their local hospital with subsequent review of their CTA imaging our multidisciplinary team meeting.

Long-term outcome data was collected from medical records and validated via the NHS Spine, part of the NHS Care Records Service managed by the Health & Social Care Information Centre (HSCIC). Long-term outcome data was collected for average length of follow-up, all-cause mortality, endoleak, and re-intervention rate.

Statistical analysis was performed with a computer-based statistical software package (Statistical Package for Social Science (SPSS) 22 for Mac, IBM Corporation, USA). Descriptive statistics were used to record outcomes for this procedure and Kaplan-Meier life table analysis used to describe survival and re-intervention free survival.

Results:

Short-term outcomes:

Primary technical success, was achieved in 51/55 (92.7%) of cases. As already discussed one patient died in-hospital from aneurysm rupture following aortic de-branching prior to TEVAR being successfully performed as a staged procedure. In a further case following transposition of the LSA, the TEVAR procedure had to be abandoned due to an inability to safely advance the stent graft system through tortuous and complex iliac artery anatomy.In two cases there was a Type 1a endoleak on completion angiogram; one case was successfully managed with a proximal cuff extension and chimney graft to the innominate artery, and in the second case the decision was made to perform no further procedures due to the deteriorating clinical condition of the patient and the endoleak was left. No conversion to an open surgical arch repair was required in any of the cases performed.

Overall 30-daymortality was 3.6% (2/55). 30-day mortality in the elective and emergency sub-groups was 2.1% (1/48) and 14.3% (1/7) respectively. Overall in-hospital mortality was 9.1% (5/55). In-hospital mortality in the elective and emergency sub-groups was 8.3% (4/48) and 14.3% (1/7) respectively. One patient who underwent an emergency complete supra-aortic de-branching and endografting for a ruptured 5.6cm arch aneurysm, together with laparotomy and thrombectomy of an occluded bypass graft placed for a previous infra-renal abdominal aortic aneurysm (AAA) graft (to facilitate stent graft placement) died 11 days post-operatively as a result of an intra-operative MI and stroke. The other patient that died within 30-dayshad a 6.2cm thoracoabdominal aneurysm,and died of an aneurysm rupture 6 days after her elective aortic de-branching procedure prior to endografting as previously discussed. Further in-hospital deaths occurred in a patient who underwent a staged zone 0 HAR followed by a 4-vessel visceral hybrid procedure for treatment of a 7.6cm Type II TAAAwho died 65 days following their initial HAR due tomulti-organ failure (MOF); another patient died due to an intra-operative stroke and MOF 70 days after an elective zone 0 HAR for treatment of a 7.5cm Type I TAAA;and the final in-hospital death occurred secondary to an intra-operative myocardial infarction (MI) and re-intervention for a RCCA-LCCA bypass occlusion 159 days after an elective zone 1 HAR was performed for treatment of 7.9cm type 1 thoracoabdominal aneurysmal dilatation of a chronic type B dissection.

29.1% (16/55) of patients required re-intervention during their hospital admission. Eight patients (14.5%) required a re-intervention for complications related to their extra-anatomical bypass grafts; five for post-operative bleeding or haematoma, and a further threewho required thrombo-embolectomy for acute graft occlusion. Four (7.3%) patients developed early endoleaks identified on post-operative CT imaging prior to discharge which subsequently required a further intervention; one patient had a type 1a endoleak which was treated successfully with a proximal cuff extension and chimney to the IA, one patient had a type 1b endoleak successfully treated with a distal cuff extension and two patients required embolization of the LSA to treat type 2 endoleaks. A further two patients developed early type 2 endoleaks identified on CT which were not treated prior to discharge. Therefore, there was an overall early endoleak rate of 10.9% (6/55). Four (7.3%) patients required further interventions during their hospital admission; one required a bronchial stent insertion for obstruction secondary to external compression by a large aneurysm sac, one patient fell on the ward post-operatively sustaining a fractured neck of femur requiring surgical fixation and a prolonged hospital stay, whilst two patients who had staged HAR and visceral hybrid procedures required re-laparotomy as a result of complications resulting from their visceral hybrid procedure; one for bowel ischaemia and one to re-vascularise both kidneys following graft failure.

14.5% (8/55) of patients had a peri-proceduralstroke (CVA) with an acute symptomatic neurological event following their procedure. The peri-procedural CVA rate in the elective and emergency cohorts was 12.5% (6/48) and 28.6% (2/7) respectively. 5.7% (3/53) of patients who had an endograft placed suffered peri-proceduralspinal cord ischaemia (SCI) with a new onset permanent or transient motor or sensory deficit following their procedure.

Long-term outcomes:

Overall mean follow-up was 74.6 months (95% CI 57.5-91.7). Mean follow-up in elective and emergency groups was 77.0 months (95% CI 58.5-95.4) and 41.7 months (95% CI 8.2-75.3) respectively. Figure 2 displays a censored Kaplan-Meier survival graph showing overall cumulative survival to 5 years. Overall cumulative survival was 70% at 1 year, 68% at 2 years and 57% at 5 years. Overall cumulative survival in the elective cohort of patients was 71% at 1 year, 71% at 2 years and 58% at 3 years. In the emergency cohort follow-up beyond 1 year was limited to a small population of only two patients and so estimates of survival are not feasible; a cumulative 1-year survival of 38% in the emergency group however highlights the importance of understanding who is at high-risk, and in whom most complications occur which may lead to early mortality and morbidity.

Figure 3. shows a censored Kaplan-Meier survival graph demonstrating cumulative re-intervention comparing the proximal landing zone to other sites in the aorta, and also overall aortic re-interventionrate during a 5-year follow-up period. Overall aortic re-intervention rates were 18% at 1 year, 21% at 2 years and 36% at five years. Re-intervention to the proximal landing zone for late 1a endoleak was minimal, with only two patients requiring intervention during the follow-up period giving an overall re-intervention rate to the proximal landing zone of 5.7% (3/53). Re-intervention to the distal aorta was more common, with a cumulative re-intervention rates of 18% at 1 year, 22% at 2 years and 30% at 5 years. Overall there were 6 type 1b endoleaks, six type 2 endoleaks and 2 type 3 endoleaks which required intervention. A further three type 2 endoleaks, and 1 type 1b endoleak were identified during follow-up which did not require intervention during that period.