Problems During the FollowUp

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21.4.1 Postimplantation Syndrome

Postimplantation syndrome can be manifested in various symptoms and signs, such as fever, leukocytosis, elevated C-reactive protein level, pleural effusion, and decreased platelet count.

Fever, leukocytosis, and elevated C-reactive protein level, of which the incidence is known to be 20-60%, are suggested to be a nonspecific systemic inflammatory reaction rather than true infection. However, it has been reported to result in little prolonged complication by many authors [20, 36]. In our early experiences, we routinely medicated prophylactic antibiotics; however, this did not help to lower the incidence of postimplantation syndrome. All the patients recovered with conservative treatments in 2-10 days. Many institutes manage these

Fig. 21.2. Emergence of hidden intimal tear. A 66-year-old man with De Bakey type III acute aortic dissection. a Preoperative aortogram demonstrates a large entry tear located at the distal descending thoracic aorta near the diaphragm (arrow). No other entry tear is defined in the descending thoracic aorta. b Immediately after the stent-graft deployment, the completion aortogram shows exclusion of the entry tear and nonvisualization of the false lumen. c,d One week after the stent-graft treatment, emergence of a hidden entry tear (arrow) is depicted just above the stent-graft on CT (c) and aortograms of 50° right anterior oblique view (d). Contrast enhancement of the thoracic false lumen is still noted complications only with anti-inflammatory agents or even without any medication and recommend judicious use of antibiotics [12, 25, 30].

Pleural effusion and decreased platelet count are not well-known complications of stent-grafts in aortic dissection. In our series, 34 patients (57%) with pleural ef fusion and 22 patients (37%) with decreased platelet count to more than 50% of the base line were observed during the follow-up. All patients with pleural effusion, which we suggest to originate from foreign-body irritation to the adjacent pleura, showed complete resolution on 1-month (n = 25) or 3-month (n = 9) follow-up CT

scans without any specific treatment. In 22 of our patients, the platelet count decreased until 1-3 days after the stent-graft placement and it recovered to the initial base line in 3-13 days (mean 5.2 days) without transfusion or any other treatment. Because all cases of platelet count drop occurred in patients whose former patent false lumens had been obliterated by thrombus formation, consumptive coagulopathy is suggested to be the cause of this transient complication.

21.4.2 Neurologic Complication

Cerebral ischemic complication is reported to occur in 3-10% of stent-grafts in aortic dissection [16, 25]. A possible embolic event might be responsible for this uncommon complication. Gentle maneuver of the guide-wire and the introducer could be the only way to lower the incidence of cerebral embolic complication. In our series, transient ischemic attack developed immediately after the stent-graft treatment in one patient (2%); this patient spontaneously recovered without any sequelae.

Our own device of separated stent-grafts was deployed upon the orifice of the carotid artery and the left SCA with the bare stent portion in 13 patients. Pannus formation did not disturb the cerebral or extremity circulation during follow-up and our cases of surgical conversion proved a wide-open carotid and SCA owing to the large cell size (1X1 cm) of the bare stent portion which had covered the branch vessels of the aortic arch. Czemark et al. [3] and Quinn et al. [28] also reported that they placed the uncovered part of the stent-graft over the ostium of the left SCA without any neurologic complication.

We have not experienced any other neurologic complications such as paraparesis or paraplegia. Although spinal ischemia has been reported by some authors [18, 19], many different authors' experiences to date permit the conclusion that the usual surgical paradigm relative to intercostal artery sacrifice and aortic clamping during open repair and its resultant incidence of spinal cord ischemic complication as much as 7-35% does not pertain to stent-graft repair [27]. Furthermore, in the case of aneurysms with partial thrombosis, many intercostal branches are already occluded and the spinal cord is perfused by collaterals. The sudden deployment of the stent-graft followed by the occlusion of the intercostal branches does not produce steal syndrome in the perfusion of the spinal cord [11]. Cambria et al. [2] observed no spinal cord complication in 28 cases of thoracic aortic stent-graft treatment. Seventy patients of Palma et al. [25] were free from paraplegia with thoracic stent-grafts. Kato et al. [16] reported one case of paraplegia developed after a surgical conversion to fix an endoleak out of 38 thoracic stent-grafts.

21.4.3 Persistent Type I Endoleak

Type I endoleak (attachment site endoleak) is known to be the most frequent complication in the stent-graft treatment of aortic dissection, which could be a potential clinical failure during follow-up [10, 18]. The percentage of type I endoleak reported in the literature ranges from 0 to 44 [4]. A proximal neck less than 2 cm from the left SCA and the existence of an entry tear located at the lesser curvature of aortic arch are known as risk factor of an endoleak [26, 33].

In our series, 12 cases (20%) of endoleaks were depicted on immediate aortograms out of 60 cases. Ten of 38 patients (26%) whose entry tears were located at the aortic arch and the proximal DTA showed an endoleak, whereas two of 22 patients (9%) with entry tears at the mid and distal thoracic aorta showed an endoleak. The distance between the left SCA and the primary entry tear was 1.5-8 cm (mean 4.1 cm) in patients with an endoleak, which was significantly shorter than in patients without an endoleak (mean 12.7 cm) (p<0.05).

In terms of the fate of type I endoleaks, there is still some debate between authors. However, many authors reported their experiences of the spontaneous healing of type I endoleaks. Lepore et al. [18] reported seven patients (16%) with type I endoleaks among 43 thoracic aortic stent-grafts. They treated three of them with additional stent-graft deployment and the others resolved spontaneously within 1 month. Shimono et al. [33] reported 80% spontaneous resolution of type I endoleaks in 37 stent-grafts for aortic dissection.

Also in our study, six (50%) of 12 patients who had demonstrated type I endoleaks on immediate angio-grams after the deployment of stent-grafts showed spontaneous thrombosis of the thoracic false lumen without any further treatment (Fig. 21.3). The duration of self-resolution was 1 week to 8 months. The other six endoleaks remained persistent on follow-up CT scans. Among them, two patients showed progressive aneurys-mal dilatation of the false lumen (Fig. 21.4). One of them underwent surgical graft replacement and the other one refused further treatment and are under close follow-up for 4 years. Four other patients did not show any remarkable changes in the size and the shape of the thoracic false lumen for 8-89 months (mean 45). In case of type I endoleaks, we suggest following the patients with repeated imaging to see if there is any change in the dissected false lumen. Surgical management could be avoided unless overt enlargement of the false lumen is detected.

Fig. 21.3. Spontaneous resolution of a type I endoleak. A 44-year-old man with De Bakey type III aortic dissection. a The aortogram demonstrates De Bakey type III aortic dissection. A primary entry tear is located on the greater carvature side 4 cm from the left subclavian artery. b After the deployment and balloon apposition of the stent-graft, contrast leakage into the false lumen at the proximal end of the stent-graft (type I endoleak) is seen (arrows). c The 1-month follow-up CT scan shows persistent contrast enhancement of the thoracic false lumen around the stent-graft. d With the further expansion of the true lumen, remodeling of the thoracic aorta is shown on the 4-month follow-up CT scan. e On the 8-month follow-up CT scan, complete resolution of the previous endoleak is demonstrated. Furthermore, the thoracic false lumen disappeared completely

Fig. 21.3. Spontaneous resolution of a type I endoleak. A 44-year-old man with De Bakey type III aortic dissection. a The aortogram demonstrates De Bakey type III aortic dissection. A primary entry tear is located on the greater carvature side 4 cm from the left subclavian artery. b After the deployment and balloon apposition of the stent-graft, contrast leakage into the false lumen at the proximal end of the stent-graft (type I endoleak) is seen (arrows). c The 1-month follow-up CT scan shows persistent contrast enhancement of the thoracic false lumen around the stent-graft. d With the further expansion of the true lumen, remodeling of the thoracic aorta is shown on the 4-month follow-up CT scan. e On the 8-month follow-up CT scan, complete resolution of the previous endoleak is demonstrated. Furthermore, the thoracic false lumen disappeared completely

21.4.4 Type II Endoleak

A type II endoleak after the stent-graft treatment is not as much a concern in aortic dissection as it is in abdominal aortic aneurysm. Sometimes, type II endoleaks through the intercostal artery can occur in aortic dissection and make contrast enhancements around the intercostal attachment sites of the false lumen. Bortone et al. [1] also reported two cases of type II endoleaks among 43 stent-grafts for type B dissection, associated with a complete thrombosis of the thoracic false lumen and an insignificant retrograde flow. Palmer et al. [26] found open and retrogradely perfused intercostal arteries in the region of the stent-graft in a patient whose thoracic false lumen was completely thrombosed. They assumed that collateral perfusion through the intercostal artery enables good residual blood flow to the spinal cord rather than a harmful effect such as endotension.

In our series, two cases of type II endoleaks (3%) through the intercostal arteries were demonstrated by follow-up CT scans taken 1 month after the stent-graft treatment. Those endoleaks did not affect the remodeling and the thrombosis in the thoracic false lumen. They resolved spontaneously after 5 and 6 months (Fig. 21.5).

21.4.5 Progressive Abdominal Aortic Aneurysm

Despite an adequate sealing of the primary entry tears in the DTA after stent-graft placement, the lack of remodeling of the abdominal aorta has been a constant problem observed by many authors. The preliminary results of Kato et al. [15] dealing with 15 chronic type B dissections showed there was no significant difference in the size of the abdominal true and false lumens even after the successful remodeling of thoracic dissection.

Flg. 21.4. Progression of the endoleak. A 70-year-old man with De Bakey type III aortic dissection. a The aortogram shows an entry tear located at the lesser curvature distal from the left subclavian artery. b After the placement of the stent-graft, an endoleak of contrast material at the proximal end of the stent-graft is detected. Balloon apposition turned out to be a failure.

Flg. 21.4. Progression of the endoleak. A 70-year-old man with De Bakey type III aortic dissection. a The aortogram shows an entry tear located at the lesser curvature distal from the left subclavian artery. b After the placement of the stent-graft, an endoleak of contrast material at the proximal end of the stent-graft is detected. Balloon apposition turned out to be a failure.

c,d Comparison of CT scans before stent-graft treatment (c) and at 1-year follow-up (d), enlargement of the descending thoracic aorta from 6.3 to 8.0 cm can be seen. This patient refused any further treatment and is under close observation for 46 months

Quinn et al. [28] reported a case of progressive aneurysmal dilatation of the infrarenal abdominal aorta after placing a stent-graft in the DTA; the aneurysms were treated by surgical repair. Lopera et al. [20] placed stent-grafts in four acute and six chronic type B dissections. Among them, two cases of abdominal false lumen rupture occurred 9 and 13 months after the procedure and all of their dissections were chronic.

Although 47 of 60 patients (78.3%) in our study achieved complete thrombosis or resolution of the tho racic aortic false lumen, complete thrombosis or resolution of dissected abdominal aortic false lumens was achieved in only five patients. During the follow-up, four patients (7%) with technical success showed progressive dilatation of the abdominal false lumen in our study and all of their dissections were chronic. The maximal diameter of their abdominal aorta was increased after the procedure from 3.9 to 4.8 cm during the mean follow-up period of 35 months. We could not find any predicting factors for this problem except the

Aortic Dissection Endoleak
Fig. 21.5. Type II endoleak. A 55-year-old man with De Bakey type III chronic aortic dissection. a Follow-up CT scan taken 1 week after the complete exclusion of the entry tear with a stent-graft shows focal contrast enhancement in the false lu

men representing a type II endoleak (black arrow) through the nearby intercostal artery (white arrow). b Five-month follow-up CT scan shows resolution of the endoleak despite the persistent enhancement of the intercostal artery chronicity of the dissection that might be related to the number of reentry tears in abdominal aorta. A patent abdominal false lumen originated from the persistent false lumen flow through multiple reentry tears of the abdominal aorta. Because reentry tears in the abdominal aorta tend to be located near the exit sites of branch vessels, it is mostly impossible to exclude those reentry tears [25]. Fortunately, because of the favorable location of the reentry site, two patients were eligible for further intervention in our study; one with three more stent-graft placements upon the reentry tears in the proximal abdominal aorta, the infrarenal abdominal aorta, and the common iliac artery 53 months after the initial stent-graft treatment (Fig. 21.6); the other one with coil embolization of reentry in the renal artery and the stent-graft over the reentry in the common iliac artery.

21.4.6 New Intimal Tear

Recently, many authors reported the formation of a new intimal tear resulting in pseudoaneurysm or dissection at the margin of the stent-graft from intimal injury as one of the most frequent complications in aortic stent-graft treatment [15, 20, 26].

In our study, we identified six cases (10%) with a new intimal tear complicating saccular aneurysms («=3) (Fig. 21.7) or new dissections («=3) developed on both ends («=1) or either end («=5) of the stent-graft. Two patients had acute dissection and four had chronic dissection. The delay between the stent-graft implantation and identification of a complicating intimal tear was 1-5 months (mean 3.2 months). Three of six patients (50%) underwent surgical conversion: one with newly developed pseudoaneurysms at both ends of the stent-graft, another with dissection due to the new inti-mal tear at the distal end of the stent-graft, and the other with retrograde type A dissection due to the inti-mal tear 6 cm above the proximal end of the stent-graft in a patient with Marfan syndrome; these were confirmed on open repair. In one patient whose previous entry tear had been located at the mid-DTA, a new inti-mal tear developed at the distal margin of the stent-graft at the level of the diaphragm. He presented acute collapse of the abdominal aortic true lumen and mesen-teric ischemia from dynamic occlusion. We deployed another stent-graft upon the new intimal tear (Fig. 21.8). The other two patients have been under close observation for 24 and 41 months.

One case of complicating type A dissection in a patient with Marfan syndrome is suggested to be related not to irritation from the stent-graft itself but to guide-wire manipulation according to the retrospective review of intraprocedural films and the surgical findings. Care should be taken in stent-graft treatment for Marfan syndrome because of its well-known instability of the aortic wall [6].

Lopera et al. [20] also reported two cases (20%) of aneurysm formation at the ends of the stent-graft in ten patients with type B aortic dissection. Both cases were successfully managed with placement of additional stent-grafts. Lepore et al. [18] reported two cases of sudden death from aortic rupture 34 and 139 days after stent-graft treatment for acute aortic dissection. Autopsy revealed perforation of the aortic wall by the

Fig. 21.6. Progressive enlargement of the abdominal false lumen. A 50-year-old woman with De Bakey type III aortic dissection. a, b Preoperative CT scans show aortic dissection involving both the thoracic aorta (a) and the abdominal aorta (b). A primary entry tear was located at the proximal descending thoracic aorta. Larger lumens are the false lumen (asterisk). c On the 46-month follow-up CT scans after the successful placement of the stent-graft upon the primary entry tear, the thoracic false lumen is completely thrombosed and regressed. d However, the abdominal false lumen is enlarged progressively from 4.8 to 6.3 cm in maximal diameter. e,f The aortogram obtained 51 months after the stent-graft treatment demonstrated multiple large reentry tears 3 cm above the celiac artery (e, arrow), 4.5 cm below the renal artery (f, small arrow), and at the exit site of the left internal iliac artery (f, large arrow). We successfully placed three consecutive stent-grafts upon each reentry tear. g Three-dimensional reconstructed CT scan no longer shows contrast enhancement of the thoracic and abdominal false lumens and patent branch vessels of the aorta

What Tue Arota

Fig. 21.7. Complicating saccular aneurysm at the proximal end of the stent-graft. A 56-year-old woman with De Bakey type III chronic aortic dissection. a The initial CT scan taken 3 months after the onset of the patient's symptom shows aortic dissection involving the descending thoracic aorta. Partial thrombosis of the false lumen is noted (arrow). Five days after the stent-graft treatment, the false lumen is excluded. c On the 2-month follow-up CT scan, a saccular aneurysm is newly developed near the proximal end of the stent-graft (arrow). This saccular aneurysm shows no demonstrable interval change on the 15-month follow-up CT scan

Fig. 21.7. Complicating saccular aneurysm at the proximal end of the stent-graft. A 56-year-old woman with De Bakey type III chronic aortic dissection. a The initial CT scan taken 3 months after the onset of the patient's symptom shows aortic dissection involving the descending thoracic aorta. Partial thrombosis of the false lumen is noted (arrow). Five days after the stent-graft treatment, the false lumen is excluded. c On the 2-month follow-up CT scan, a saccular aneurysm is newly developed near the proximal end of the stent-graft (arrow). This saccular aneurysm shows no demonstrable interval change on the 15-month follow-up CT scan proximal end of the stent-graft. Also in our three surgical converted cases, intimal tears were clearly depicted. Kato et al. [16] reported five cases (13.2%) of new aneurysm formation after the stent-graft repair for 38 aortic dissections. The intervals between the diagnosis and notification of the aneurysms ranged from 17 to 99 days (mean 63 days). Additional stent-graft placement and surgical graft replacement were performed for the management of these patients. All of their five patients were admitted owing to acute dissection and all of the newly developed aneurysms were located at the curved portion of the DTA that attached the stent-graft at an angle. Similarly, five of our six intimal tears developed at the curved portion of aorta where the stent-graft and the intima meet at an angle. Many articles dealing with stent-graft treatment suggest that the causes of the development of intimal tears are mechanical intimal injury, stent-graft migration, and weakened aortic wall. They also suggest several methods to avoid these complications; first, the stent-graft should cover longer portions of the descending aorta until it fits the parallel portion of the aortic wall or intima; second, development of stent-grafts with smoother edges and more flexible bodies [16]. During our early phase of study, we assumed that acute dissection should be more vulnerable in the formation of complicating pseudoaneu-rysm rather than chronic dissection because of the unstable and fragile intima. However, four of six patients with this complication were managed from chronic dissection and there was no relationship between the duration of the aortic dissection and the development of complicating pseudoaneurysm or dissection. We consider the mechanical stress by the sharp stent tip, the in flexibility of the stent-graft, and the pulsatile force of the aorta have as much adverse effect as the instability of acutely dissected intima. Another possible reason we assume is diaphragmatic motion in the fixed aorta because two of these six intimal tears were located near the diaphragmatic portion of the descending aorta. We also consider ballooning for the purpose of stent-graft apposition as one of the possible etiologic factors of the complicating intimal tear and we do not routinely perform the balloon apposition in stent-graft treatment of aortic dissection. As demonstrated, it is imperative to be aware of the possibility of an intimal tear on both ends of the stent-graft during follow-up.

21.4.7 Mechanical Failure of the Stent-Graft

Since the first stent-graft was placed for the treatment of aortic disease, this technique has improved remarkably with growing understanding of metallurgic and fabric sciences. However, mechanical failure from stent-graft materials of metal and graft continues to be a potential problem in aortic stent-graft treatment. The inherent properties of the resistance of the materials (strength and corrosion) combined with extrinsic forces contribute significantly to the risk of device fatigue. Before deployment, the metallic stent may experience increased risk for failure as a result of damage during loading and subsequent confinement in the delivery catheter. Once implanted, the device is then subjected to additional extrinsic forces imposed by the geometry of the tortuous aorta and the impact of continuous,

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high-pressure blood flow. Mechanical failure of the stent-graft can occur in the form of metallic fracture, fabric wear, and suture breakage. Recent large series by Jacobs et al. [13] identified 60 patients (9%) with mechanical failure of the stent-graft out of 618 patients who underwent aortic stent-graft placement. Forty-three of them had metallic stent fracture, 14 suture disruption, and three graft wear. The average time to the recognition of mechanical failure of the prosthesis was 19 months. Six of them resulted in surgical conversion and the other ones have been asymptomatic and have not needed interventions for device fatigue. They recommend that if a patient is asymptomatic and there is no evidence of disease progress or a type I or type III endoleak, observation of the stent graft fatigue is acceptable in the setting of increased graft surveillance.

In our series, two cases (3%) with mechanical failure were identified: one with metallic fracture and the other with fabric wear. Metallic fracture was found 36 months after the initial stent-graft placement. Fabric wear occurred at the proximal portion of the graft and made an endoleak around the tear site. However, they have had further complications such as false lumen enlargement or rupture for 56 and 69 months.

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