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Interact CardioVasc Thorac Surg 2009;9:61-65. doi:10.1510/icvts.2008.196402 © 2009 European Association of Cardio-Thoracic Surgery
Mid-term results of thoracic endovascular aortic repair in surgical high-risk patients
a Department of Cardiothoracic Surgery, Juan Canalejo Hospital, La Coruña, Spain Received 20 October 2008; received in revised form 16 March 2009; accepted 17 March 2009
*Corresponding author. Department of Cardiac Surgery, Hospital Juan Canalejo, As Xubias n°84, CP 15006, A Coruña, Spain. Tel.: +34-981178000 (ext. 298814)/+34-699054009; fax: +34-981178299.
Between May 2001 and June 2008, the outcome and morphological changes in thoracic aortic lesions of 20 surgical high-risk patients who underwent TEVAR were evaluated. Aortic lesions included 8 (40%) type B dissections, 5 (25%) atherosclerotic aneurysms, 4 (20%) penetrating ulcers and 3 (15%) traumatic aortic ruptures. All patients were classified as American Society of Anaesthesiologists class IV and obtained high scores in both the logistic European System for Cardiac Operative Risk Evaluation, median of 14.5% (range 8.1–65.7%), and the STS Parsonet 95 scoring system, median of 14 (range 10–52). Endovascular stent-graft deployment was technically successful in all cases. No surgical conversion occurred. Early mortality was observed in two patients. Clinical and imaging follow-up was available in all patients at a median time of 28 months (range 4–89 months). Overall actuarial survival was 90% at one and five years and 60% at seven years. Mean diameter of the descending aorta decreased from 51.1±13 mm to 45.3±8 mm (P=0.032). Mean reduction in dimension of aneurysms was 10.7±8 mm. Endovascular thoracic aorta repair will probably benefit more patients with multiple comorbidities that limit their life expectancy than patients with a lower profile.
Key Words: Thoracic aorta; Aneurysm; Peripheral vascular
Lesions involving the descending aorta tend to occur in high-risk patients and pose a challenging surgical problem. Despite advances in surgical and critical care technology, open thoracic aortic surgery is still associated with a very significant morbidity and mortality [1]. The presence of many medical comorbidities in this specific patient population increases the surgical risks, especially in cases of emergency operation for aortic rupture [2–4]. Endovascular stent-graft repair of descending thoracic aortic aneurysms started at Stanford in 1992 as a less invasive alternative to conventional open surgical graft replacement [5, 6]. In early reports, stent-graft treatment was usually reserved for poor candidates for open operation [5]. The purpose of this study is to evaluate the mid-term outcome, complications and morphological changes in thoracic aortic lesions of high-risk patients following an endovascular treatment.
Between May 2000 and June 2008, 20 patients (15 male, mean age of 63.5±13.6 years), underwent endovascular thoracic aortic repair with the Talent® or the Valiant® (Medtronic, World Medical Manufacturing Corp, Sunrise, FL) thoracic stent-grafts. Aortic lesions included 8 (40%) type B dissections, 5 (25%) atherosclerotic aneurysms, 4 (20%) penetrating ulcers and 3 (15%) traumatic aortic ruptures (Table 1). The indications for acute lesions were traumatic rupture of the isthmus, type B dissections with malperfusion syndrome (Fig. 1) or signs of aortic wall rupture and ruptured aneurysms and penetrating ulcers with signs of aortic wall rupture or bleeding (Fig. 2). The chronic lesion indications were aneurysms >50 mm and progressive penetrating ulcers of the descending thoracic aorta (Fig. 3). All patients were classified as American Society of Anesthesiologists (ASA) class IV. Patients were also classified according to the scores obtained in both the European System for Cardiac Operative Risk Evaluation (EuroSCORE), median logistic EuroSCORE value of 14.5% (range 8.1–65.7%), and the STS Parsonet 95 scoring system, median Parsonet score of 14 (range 10–52) (Table 1). All patients had been considered unsuitable candidates for conventional open surgical repair. Previous cardiac or abdominal aortic surgery were reported in 4 (20%) and 2 (10%) patients, respectively. Mean aortic diameter for the aortic dissection and the aneurysms was 49.8±12.5 mm. Regarding the thoracoabdominal aneurysm Crawford classification, we treated three type I lesions, one type II and one type III lesions. No type IV thoracoabdominal aneurysm was included in this series. The proximal landing site was zone 2 in 6 (30%) patients, while the remaining covered zones 3–4. The stent landing zones are summarized in Fig. 4. The endografts deployed in zone 2 were navigated so that the Floppy Freeflo Straight portion of the Talent® or the Valiant® (Medtronic, World Medical Manufacturing Corp, Sunrise, FL) thoracic stent-grafts, which has a proximal bare spring and allows the blood flow through it, covered partially the origin of the left subclavian artery (LSA).
2.1. Statistical analysis The SPSS statistical program for Windows version 13.0 (SPSS, Chicago, Illinois) was used to perform the data analysis. Data are expressed as mean and S.D. or median and range, when appropriate. Discrete variables were analyzed by the Wilcoxon signed rank test. The paired t-test was used to analyze continuous data. Categoric variables were compared with contingency tables by means of  2 or Fisher exact tests, where appropriate. A P-value <0.05 was considered significant. Actuarial estimates of survival were accomplished with Kaplan–Meier methods.
Anatomic conditions that allowed endovascular stent placement were assessed in each patient at contrast-enhanced 64-slide computed tomography (CT) LightspeedTM VCT General Electric Company (NYSE:GE) or at 1.5-Tesla Philips InteraTM cardiovascular magnetic resonance imaging system (CV MRI) (Philips Medical Systems, Best, The Netherlands). Information on maximum aneurysm diameter or on dissection size, proximal and distal anatomic extension, and distance from the LSA were recorded. The carotid arteries, the vertebral arteries and the Circle of Willis were fully assessed either by angiography or by 64-slide CT scanning when risk of occluding the LSA was present. An absent right vertebral artery, diseased carotid arteries or an incomplete Circle of Willis was considered a contraindication to LSA coverage without prior transposition or bypass grafting of the LSA. 2.3. Stent-graft systems and interventional endovascular procedure Endovascular stent placement procedures were performed in the operating room with patients receiving general anesthesia. Cardiopulmonary bypass was available on a standby basis during every stent placement procedure. A team of two cardiovascular surgeons and two interventional radiologists worked together. All procedures were monitored with a portable radiographic C-arm system Philips BV PulseraTM (Philips Medical Systems, Best, The Netherlands) with digital subtraction angiography (DSA).CT images were used to calculate stent-graft dimensions, which were oversized by 10–15% compared with the landing zone diameters (not in dissections or aortic ruptures). The stent-graft length was at least 30–40 mm longer than the target lesions to ensure adequate wall contact and a tight circumferential seal in the landing zones. Several stent-grafts [2, 3] were used in six patients, taking into account a 50% overlap. A final aortogram was performed to confirm the right positioning of the stent-graft and exclusion of the lesion. When the LSA was covered by the stent fabric, the most proximal segment of the subclavian artery was occluded with coils to prevent a late type II endoleak. 2.4. Clinical and imaging follow-up All patients underwent helical CT or CV MRI, depending on availability, at intervals of 1, 3, 6, and 12 months after the procedure and yearly thereafter. CT and CV MRI protocols were the same as those used for the preoperative evaluation.The parameters evaluated were as follows: absence of flow within the aneurysmal sac, aneurysm dimension, morphology of the stent-graft (i.e. position and configuration of the metallic frames, eventual kinking or rotations, irregularity of the aortic profile), and diameter and wall morphology of the proximal and distal neck. In patients treated for aortic dissection, the perfusion of abdominal vessels, especially those arising from the false lumen, was also evaluated.
Endovascular stent-graft insertion and deployment was technically successful in all cases. No surgical conversion and intra-operative mortality occurred. In 14 patients, the positioning of one stent-graft segment was sufficient to achieve aneurysm sealing or closure of the entry site of dissection, whereas in six patients, the positioning of two or three segments was required. The mean length of aortic coverage was 139.2±24.5 mm. The distance between the LSA and the aneurysm was <20 mm in 12 patients. In one case the intraoperatory control angiography suggested to us that LSA should be occluded to prevent a later endoleak. The most proximal segment of the subclavian artery was occluded with MReye® Embolization Coils 0.035''–5 cm–8 mm (Cook Diagnostic and Interventional Products, William Cook Europe, Denmark, DK) via a right brachial approach. Neither neurological nor limb ischemic complications were identified in this patient. Early mortality was observed in two patients. One patient who presented a complicated acute type B dissection died on the 12th postoperative day of septic shock caused by intestinal ischemia in spite of the performance of emergent fenestration and stenting to release the compromised mesenteric perfusion. The other patient presented a ruptured Crawford type I thoracoabdominal aneurysm with massive left hemothorax and died on the second postoperative day from multiorgan failure after hypovolemic shock and acute respiratory distress syndrome secondary to multiple blood transfusions. The median intensive care unit stay was two days (range 1–25 days), and the median hospital stay was eight days (range 3–30 days). Two patients (10%) developed neurological complications. One patient presented transient left superior limb monoparesis and the other developed a partial Brown-Séquard syndrome characterized, in this case, by left lower limb paresis with hypalgesia more marked on the right lower limb. The latter presented an acute aortic type B dissection on a Crawford type I thoracoabdominal aneurysm which was repaired without over-stenting the LSA. Transient post-implantation syndrome with mild leukocytosis, elevated levels of C-reactive protein, and moderately elevated body temperature occurred in three patients (15%). Clinical and imaging follow-up was available in all patients at a median time of 28 months (range 4–89 months). One patient died of congestive heart failure 63 months after the procedure. Overall survival estimated by the Kaplan–Meier method, including early mortality, was 90% at one and five years and 60% at seven years (Fig. 5).
Only one patient needed a re-intervention because a late endoleak at 23 months of follow-up, which means a cumulative proportion surviving free of re-interventions of 90% at 23 months. This late type III endoleak was detected in a patient who had been treated firstly with a 100-mm endograft and suffered a dislocation and structural damage of the distal stent-graft, causing the endoleak. A new re-intervention and deployment of another endograft was performed to successfully seal the endoleak. Progressive reduction in size of the thrombosed aneurysm or the thoracic false lumen was observed during the follow-up in 14 patients (70%). In patients with six months of follow-up and with aneurysm or false-lumen shrinkage, the mean diameter of the descending aorta decreased from 51.1±13 mm before the stent-graft procedure to 45.3±8 mm at the latest available follow-up imaging study after the procedure (P=0.032). The mean reduction in dimension of aneurysms was 10.7±8 mm.
The surgical repair of the descending aorta has the risks of high morbidity and mortality. A meta-analysis recently published by Walsh et al., compares outcomes between endovascular and open surgery. The analysis demonstrated a significant benefit for stenting with respect to perioperative mortality and major neurological injury [7]. Attia et al. presented a series of 75 consecutive patients undergoing TEVAR with a survival rate at 12 months of 84% and at 36 months of 80% [8]. Demers et al. reported a satisfactory survival after aneurysm repair using first-generation stent grafts in good operative candidates but bleak in the inoperable cohort, raising the question of whether asymptomatic patients should have even been treated [2]. The population affected often is elderly, and these patients frequently have associated diseases that can determine a high surgical risk [9, 10]. All patients included in our series were classified as ASA class IV. Moreover, these patients obtained high scores in both the EuroSCORE and the STS Parsonet 95 scoring system. Indeed, actual perioperative mortality for this series, two patients (10%), was significantly lower (P=0.037) than the expected perioperative mortality (14.5%). EuroSCORE and Parsonet score systems are not probably suitable score systems to estimate the surgical risk in endovascular procedures. We strongly believe that a new, validated score system, exclusively addressed to endovascular procedures, should be developed. Nevertheless, even with that drawback, these scores are useful because they provide information about what the expected mortality for the thoracic aorta pathologies would have been if an open surgery had been attempted. These scores reflect the strong differences on morbimortality between open surgery (mortality calculated by the scores) and the endovascular procedures (mortality reflected in our and many other series) when dealing with these pathologies. Overall survival at one, five and seven years was 90%, 60%, and 60%, respectively, which was also considerably lower than the expected survival for a population matched for age and gender. The TEVAR of the proximal descending aorta (especially zone 2) and/or the over-stenting of LSA, together with high-grade aortic atheroma of the aortic arch and previous stroke, predicted a high probability for cerebral embolization risk for stroke as a consequence of TEVAR [11]. The proximal landing zone has been zone 2 in six of our cases, resulting in a partial or complete coverage of the LSA. Notwithstanding, we strongly believe that before doing that, the carotid arteries, the vertebral arteries and the Circle of Willis should be fully assessed either by angiography or by 64-slide CT scanning when risk of occluding the LSA is present. As we have previously reported [12], in most of the cases in which the landing zone was in the distal arch, the Floppy Freeflo Straight portion of the Talent® and the Valiant® endograft (Medtronic, World Medical Manufacturing Corp, Sunrise, FL), which has a proximal bare spring, may be deployed allowing the blood flow through it and preserving the LSA patency. Endoleaks, especially type I, are associated with persistent or recurrent aneurysmal sac pressurization, progressive expansion, and eventual rupture [13–15]. We advocate for an aggressive endoleak treatment when found. In the long-term, changes of aneurysm morphology and dilatation of the aortic wall at the neck sites seem to constitute the major cause of treatment failure. In our study, significant device migration was only observed in one case during follow-up, leading to a type III endoleak which needed a new endograft deployment to seal the defect. In conclusion, endovascular thoracic aorta repair will probably benefit more patients with multiple comorbidities that limit their life expectancy than patients with a lower profile. However, long-term follow-up is necessary to assess the durability and effectiveness of this therapy. It is also necessary to develop specific, new surgical risk score systems to estimate the surgical risk and expected mortality for those patients undergoing an endovascular repair of aortic arch and descending aorta.
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Abstract
1. Introduction
