| IntroductionAcute type B aortic dissection (TBAD) is a fatal disease with significant early and late morbidity and mortality.[1-3]Owing to favorable30-day and1-year mortality rates, recent studies suggested that TEVAR is an acceptable treatment in the setting of acute complicated type B dissection with refractory pain and uncontrolled hypertension, despite optimal medical therapies, malperfusion, rapture or impending rupture, and acute aortic enlargement.[4,5]However, the latest research also revealed that, for uncomplicated type B dissections, TEVAR could improve the5-year aorta-specific survival and delay disease progression.[6] The exclusion and the thrombosis of the false lumen, with the re-expansion of the true lumen, are the primary goals of TEVAR.[7]According to previous studies, most patients undergoing TEVAR had significant shrinkage of the false lumen and expansion of the true lumen.[8,9] It is well-known that an increase in the aortic diameter raises the risk of rupture, which is the most common cause of aorta-related mortality.[10] As a consequence, the imaging changes after TEVAR are important predictors of patient outcomes. Whereas an immediate type la endoleak is regarded as a treatment failure, and requires immediate further treatment by TEVAR for aortic thoracic aneurysms [11], the clinical significance of the immediate type Ⅰa endoleak in TBAD is unknown. In this study, we sought to identify the outcomes and the postoperative aortic morphological changes and compare them in patients with and without immediate type la endoleaks.MethodsPatients. Patients presenting to our institution from January2012to June2012with acute Stanford type B aortic dissection and treated with TEVAR were added to a prospective cohort. Demographic and clinical factors, including age, gender, personal history, indications for the procedure, operative details,30-day and1-year mortality, postoperative complications, and morphological changes were collected prospectively but reviewed in a retrospective fashion for this study.Acute dissection was defined as a presentation occurring≤14days from the onset of symptoms. Imaging analysis required patients to have both pre-and postoperative computed tomography angiography (CTA), so that measurements can be compared. Therefore,54of81patients were enrolled for imaging analyses. Patients with Stanford type A dissections were excluded from the study.Data collection. Patients underwent imaging with non-contrast and contrast-enhanced, thin-sliced (range,1-2.5mm), spiral CT (64-Multidetector Light Speed VCT, General Electric) with multi-layer reconstruction of the chest, abdomen, and pelvis for preoperative strategy-making. Patients were then prospectively followed at1,6, and12months, unless follow-up findings required more frequent observation. Patients were arranged for CTA assessment of aortic remodeling at the1-year follow-up.Pre-and postoperative CTAs were analyzed using the TeraRecon Aquarius Intuition Edition software (Foster City, CA). In patients with several postoperative CTAs, the scan with the longest follow-up was used for postoperative imaging calculations. The centerline of the true lumen (TL) and false lumen (FL) was established from the left subclavian artery (LSA) to the aortic bifurcation. On cross-sectional images, a series of manually placed points created an outline marking the edge of the true lumen, false lumen, and total aorta (Figure1), allowing thereby the cross-sectional area to be measured. Three selected aortic segments were made below the left subclavian artery, at the carina level, and at the celiac artery level of the descending thoracic aorta (Figure2). Indices of the true lumen (TLi) and the false lumen (FLi) were calculated by dividing their respective areas by the whole aortic area.Postoperative false lumen thrombosis was defined as observing an absolute lack of contrast flow in the false lumen throughout the level of stent-graft or the exclusion of the false lumen. Any contrast in the false lumen, even in the setting of partial thrombosis, was considered as showing false lumen patency.Operative details. The implantation protocol was previously published.[12,13] Stent-grafts were deployed proximally, with or without coverage of the left subclavian artery, to obtain an adequate landing zone for sealing the primary entry. Most patients were treated with one stent, unless the initial graft did not cover the entry tear and the expansion of the true lumen. In our institution, temporarily rapid artificial cardiac pacemaker was performed intra-operatively to lower the blood pressure when deploying the grafts. Routinely selected stents were at least10%-15%oversized.Definitions. An immediate type la endoleak indicates leakage at the proximal graft attachment site that is observed via intraoperative angiography (Figure3). All the definitions used in this study meet the reporting standards for TEVAR published in2010by the Society of Vascular Surgery [2] and the standardized definitions and clinical endpoints in trials investigating endovascular repair of aortic dissections published in2013by the European Journal of Vascular and Endovascular Surgery.[3]Statistical analysis. Data are expressed as means and standard deviations. Comparisons of continuous variables were made using the Student t test for independent variables. Categorical variables were compared using the Chi-square test. Fisher’s exact test was used when necessary. Differences were considered significant if the two-sided P value was≤0.05. All statistical analyses were conducted using the SPSS13.00(SPSS Inc, Chicago,Ill) statistical software.ResultsFrom January2012to June2012, a total of81consecutive patients underwent TEVAR for acute type B aortic dissection at our institution. Available demographic and clinical factors are detailed in Table Ⅰ and show that the baseline information for the two patient groups was similar. Among the participants,37(45.7%) patients were diagnosed with an immediate type Ⅰa endoleak. Thirty-six of the81patients presented complications, including persistent pain (19/36,52.7%), drug-resistant hypertension (4/36,11.1%), and end-organ ischemia (13/36,36.1%). TEVAR was successfully performed in all patients (mean age,53years;86%men). The left subclavian artery (LSA) was intentionally covered in24(65%) patients with immediate type Ⅰa endoleaks and in28(64%) patients without immediate type Ⅰa endoleaks. No statistically significant differences were seen between the groups (p=0.98). Revascularization was performed in15(40%) patients with immediate type Ⅰa endoleaks, significantly more than in the other group [15(40%) vs.4(9%), p=0.001]. Operative details are summarized in Table Ⅱ. The average postoperative follow-up was12months (range,10-13months) after the initial procedure.Five patients died, giving a30-day mortality of13.5%in the group with immediate type la endoleaks. Among them,2people presented aortic rupture2and3days after the stent-graft implantation and discharge, respectively. The emergency echocardiogram showed a large amount of pleural effusion in the right lung of the first patient. Two other people died of complications related to retrograde dissection before discharge. They presented the same signs of pericardial tamponade confirmed by an echocardiogram. The last patient died of multiple organ dysfunction syndrome (MODS) in our intensive care unit (ICU). This patient presented severe symptoms of acute mesenteric ischemia after the onset of dissection. He underwent emergency TEVAR and the angiography did not identify the superior mesenteric artery (SMA). The stent-graft was successfully deployed. However, the patient’s symptoms did not subside, and emergency exploratory laparotomy was performed, which revealed SMA thromboembolism, extensive bowel necrosis, and gangrenous cholecystitis. His recovery was complicated by refractory infections and acute renal failure, and the family eventually withdrew care. One patient died of causes related to rupture within30days in the group that did not present immediate type la endoleaks. No statistically significant differences for the30-day mortality were found between the2groups (13.5%vs.2.2%, P=0.08). During the1-year follow-up, one additional patient died in each group2and3months, respectively, after discharge. In a comparison of the1-year all-cause mortality, no significant differences were found between the2groups (16.2%vs.4.5%, P=0.13). The in-hospital complications are summarized in Table Ⅲ.Pre-and postoperative CTA images were available for analysis in54patients. The morphological changes of the proximal, middle, and distal areas of the true lumen (TL), false lumen (FL), and whole lumen during the follow-up period are presented in Table Ⅳ. In the preoperative phase, patients with an immediate type Ⅰa endoleak had a significantly larger distal false lumen area (498±274vs.284±213mm2, P=0.02) and a larger distal aortic area (759±275vs.624±185mm2, P=0.03). In the postoperative phase, the distal area of the true lumen in patients with type Ⅰa endoleaks was significantly smaller, while a significantly larger false lumen area and whole lumen area, including the proximal, middle, and distal zone of the descending aorta, were observed in patients with type la endoleaks. Area index data assessed the relative area of the true or false lumen with respect to the whole aorta area (Table Ⅴ). After eliminating interference by individual differences, the patients with immediate type la endoleaks had significantly smaller true lumen indices (TLi) and larger false lumen indices (FLi) at different levels of the aorta, which confirmed the findings of the absolute area analysis. The postoperative maximal area of the whole lumen was statistically significant in patients with an immediate type la endoleak (Table VI).At the1-year follow-up,19(51.3%) of37patients developed false lumen thrombosis throughout the entire length of the stent graft in the group with immediate type la endoleaks. No significant differences were found between the two groups [19(51.3%) vs.25(56.8%), P=0.69]. Ten patients had endoleak formation. Two of10patients required a secondary intervention procedure. In their case, delayed type Ⅰa endoleak was detected via postoperative CTA at the follow-up. The patients did not present any symptoms and were treated with TEVAR, with stents that were deployed at the relative proximal zone of the aorta. No immediate endoleaks were found by intraoperative angiography. The3out of10patients presented type II endoleaks that came from the celiac trunk and intercostal arteries. The remaining5patients were categorized as presenting type Ib endoleaks, and retrograde flow was clearly demonstrated, in their case, from the distal part of the stent graft. The difference between the rates of postoperative endoleaks was not significant between the two groups (Table Ⅵ).Conclusion.Immediate type la endoleaks are not a rare phenomenon after TEVAR in patients with acute type B aortic dissection. Most of these events could seal spontaneously, without the need for additional procedures. Nevertheless, the appearance of such complications could be an indication of worse aortic condition, and the impact of more ineffective morphological remodeling should not be underestimated. Clearly, more data and studies are needed to evaluate the risks of immediate type la endoleaks over time, and careful surveillance in patients with immediate type la endoleaks is recommended. |
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