Abstract:Minimizing the preprocedure distal oversizing ratio with a distal small graft-first procedure could reduce the risk of late distal SINE for Stanford type B aortic dissection. Furthermore, the area ratio is a potentially more sensitive modality for size assessment and prediction of distal SINE occurrence.
“…However, they did not analyze the aortic stress after SG implantation, which should be taken into consideration after TEVAR for ascending aorta with more motion than descending aorta. It has been a general consensus that RTAD can be caused by SG injury 6,7,22‐25 …”
Retrograde type A dissection after thoracic endovascular aortic repair has been a major drawback of endovascular treatment. This study investigated the biomechanical mechanism of stent‐graft‐induced new lesions after implantation and analyzed the relationship between radial force and spring‐back force of the stent‐graft when it was implanted virtually under different oversizing ratios. Based on the computed tomography angiography images, a three‐dimensional geometric model of a patient‐specific aortic dissection was established. The stent was designed in CAD software and the stent‐graft implantation procedure under different oversizing ratios was simulated in the finite element analysis software. Implantation simulations were performed six times for each stent‐graft model under 0%, 3%, 6%, 9%, 12%, and 15% oversizing ratios and the peak stress of the aorta was compared among groups. It was observed that the peak stress of the aorta was located where the proximal bare stent interacted with aortic wall and its value was increased by 62.2% from 0% to 15% oversizing ratio. The conclusions are reached that the long‐term higher stress in the aortic wall may lead to the emergence of new lesions in these areas, and the radial force plays a key role in the formation of a new entry in the real aorta model.
“…However, they did not analyze the aortic stress after SG implantation, which should be taken into consideration after TEVAR for ascending aorta with more motion than descending aorta. It has been a general consensus that RTAD can be caused by SG injury 6,7,22‐25 …”
Retrograde type A dissection after thoracic endovascular aortic repair has been a major drawback of endovascular treatment. This study investigated the biomechanical mechanism of stent‐graft‐induced new lesions after implantation and analyzed the relationship between radial force and spring‐back force of the stent‐graft when it was implanted virtually under different oversizing ratios. Based on the computed tomography angiography images, a three‐dimensional geometric model of a patient‐specific aortic dissection was established. The stent was designed in CAD software and the stent‐graft implantation procedure under different oversizing ratios was simulated in the finite element analysis software. Implantation simulations were performed six times for each stent‐graft model under 0%, 3%, 6%, 9%, 12%, and 15% oversizing ratios and the peak stress of the aorta was compared among groups. It was observed that the peak stress of the aorta was located where the proximal bare stent interacted with aortic wall and its value was increased by 62.2% from 0% to 15% oversizing ratio. The conclusions are reached that the long‐term higher stress in the aortic wall may lead to the emergence of new lesions in these areas, and the radial force plays a key role in the formation of a new entry in the real aorta model.
“…1. TR: pre-TR = 1 - (A DLZ /A PLZ ); post-TR = 1 - (A DLZ ’/A PLZ ’),14 where A DLZ is the TL area of the presumed DLZ before TEVAR, and A PLZ is the area of the presumed proximal landing zone (PLZ) before TEVAR. A DLZ ’ is the TL area of the DLZ after TEVAR, and A PLZ ’ is the area of the PLZ after TEVAR (Figures 2 and 3);Figure 2The definitions and mathematical measurements of the taper ratio (TR), the oversizing ratio (OR) and the mismatch rate (MR) before TEVAR.…”
Section: Methodsmentioning
confidence: 99%
“…2. OR: pre-OR = (A SG /A DLZ ) - 1; post-OR = (A SG ’/A DLZ ) – 1,14 where A SG is the distal area of the fully expanded stent graft before TEVAR, A SG ’ is the distal area of the partially expanded stent after TEVAR, and A DLZ is the TL area of the presumed DLZ before TEVAR (Figures 2 and 3);…”
BackgroundThis study aims to investigate the descending aortic morphological alterations caused by pathological changes in acute and chronic Type B aortic dissection (TBAD) and morphological remodeling after thoracic endovascular aortic repair (TEVAR).Patients and methodsFrom February 2012 to January 2016, 86 TBAD patients undergoing TEVAR were divided into an acute group (n=63) and a chronic group (n=23). The areas of the true, false and maximal lumen and descending aorta morphological parameters, including the taper ratio (TR), oversizing ratio (OR), mismatch ratio (MR), radius of curvature (RoC) and tortuosity index (TI), were evaluated. Follow-ups were performed postoperatively before discharge, at 1 and 6 months, and yearly thereafter.ResultsBefore TEVAR, the TR (0.57 (0.49) vs 0.74 (0.60); P < 0.05), OR (2.75 ± 1.89 vs 3.96 ± 2.27; P < 0.05) and TI (1.22 (1.19) vs 1.41 ± 0.17; P < 0.05) were significantly higher in the chronic group than in the acute group. The TEVAR technical success rate was 100%. No differences were found in 30-day and >30-day mortality between the two groups. Pathology-specific devices, such as tapered stent grafts and distal bare stents, were used more frequently in the chronic group than in the acute group (47.8% vs 23.8%, P = 0.03; 43.5% vs 12.7%, P = 0.002, respectively). The OR and TI changes that occurred after TEVAR were significantly higher in the chronic group than in the acute group (1.80 ± 0.86 vs 2.98 ± 1.85, P = 0.028; 0.00 ± 0.09 vs 0.09 ± 0.10, P < 0.001, respectively).ConclusionTEVAR is a safe and effective therapy for acute and chronic TBAD. Compared to acute TBAD, chronic TBAD resulted in an adverse preoperative descending aorta morphology. Pathology-specific devices may be a feasible treatment option for endovascular repair of chronic TBAD. A larger series of cases with longer follow-up are needed to draw definitive conclusions.
“…X SG is the distal area of the partially expanded stent after insertion. 7 TI was defined as the intra-aorta midline length divided by the linear distance between the left subclavian artery and the celiac trunk. 22 TL expansion was assessed separately at the level of the descending thoracic aorta and the abdominal aorta (divided at the level of the celiac trunk).…”
PurposeThe aim of this study was to present our experience and assess the morphologic changes of the descending aorta after the restrictive bare stent (RBS) technique in the treatment of type B aortic dissection (TBAD).Patients and methodsA retrospective study was conducted of 22 consecutive patients with TBAD who underwent RBS treatment between February 2012 and June 2016. Indications for the RBS procedure included radiological evidence of true lumen (TL) compression or collapse and/or tortuosity index (TI) of the descending aorta >1.4. Technique success, descending aorta morphology, and clinical outcomes were evaluated.ResultsThe technical success rate was 100%. Patients treated with the RBS technique were often accompanied by TL collapse (45.5%) or TI >1.4 (59.1%). One-month postoperative computed tomography angiography showed that the taper ratio, oversizing ratio of the stent graft, and TI values were significantly decreased compared with preoperative computed tomography angiography values (P<0.05). The 30-day mortality rate was 0%. In total 95.2% had a thrombosed false lumen in the segment of aortic coverage, and TL diameters were increased in 40.3%±11% (mean ± SD) and 37.5%±17.9% of patients in the thoracic and abdominal segments, respectively. During the follow-up from 16 to 64 months (33±19 months), no distal stent graft-induced new entry, endoleak, and paraplegia were observed. One patient died from rupture of a chronic TBAD with aneurysm degeneration.ConclusionMid-term outcomes showed RBS to be a flexible and feasible approach to repair TBAD. RBS corrects the descending aorta morphology and promotes TL expansion in most patients, but the rupture of chronic TBAD with aneurysm degeneration was not prevented in all patients.
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