Basic Science ResearchStent-Graft Deployment Increases Aortic Stiffness in an Ex Vivo Porcine Model
Introduction
Thoracic endovascular aortic repair (TEVAR) has shown to be a safe treatment option for patients with thoracic aortic disease, in particular in those with severe comorbidities.1, 2 Current stent grafts offer high degrees of conformability to the native aorta. Nonetheless, computer-simulated models show that they are characterized by a certain degree of stiffness, dependent on the type of graft material.3 Aortic stiffness is an important hemodynamic parameter that has become recognized as an independent predictor of cardiovascular death.4 Understanding the effects of TEVAR on aortic hemodynamics may play a role in successfully maintaining the delicate circulatory balance of TEVAR patients, but many of these effects remain unknown. Since the velocity of a pulse wave along an artery is positively related to the stiffness of this artery, aortic stiffness can be adequately quantified by measuring aortic pulse wave velocity (PWV).5, 6 In the present article, we report the results of experimental measurements of aortic PWV before and after TEVAR, to test the hypothesis that aortic stiffness increases after TEVAR.
Section snippets
Preparation of Porcine Aortic Specimens
Fifteen thoracic aortas of healthy pigs of a hybrid breed (10- to 12-month-old, 160–180 kgs) were used. No pigs were sacrificed specifically for the purpose of this study; therefore, ethical approval by the local ethics committee was waived. The aortas were collected within 30 min after slaughter and transported at 4°C in isotonic saline solution and used for experiments on the same day. Each specimen was surgically prepared from the aortic root to the celiac trunk by removing excess connective
Results
Baseline characteristics of the 15 aortas can be seen in Table I. A 26-mm proximal diameter stent graft was deployed in 13 cases, and for the remaining 2 cases a 24-mm stent graft was used. For the distal extension, a 22-mm diameter stent graft was used in 14 cases and a 26-mm stent graft in one case. Main results can be seen in Table II. Mean aortic PWV was 5.0 m/s at baseline. Proximal stent-graft deployment caused a 4.0% increase in PWV to 5.2 m/s (P = 0.09), and stent-graft extension
Discussion
The present study was conducted to assess aortic stiffness before and after stent-graft deployment by measuring PWV in fresh porcine aortas. A moderate change in PWV was seen after stent-graft deployment with a stent-graft length of 15 cm, but a marked increase was seen when stent-graft length was extended. The increase in PWV may be limited when a shorter part of the aorta is stented, possibly because nonstented aortic segments are able to compensate for the stiffer stented part. When the
Conclusions
Stent-graft deployment increased aortic stiffness and pulse pressure in this ex vivo pulsatile porcine model, especially with greater stent lengths. These observations might have important consequences for clinical practice. Therefore, aortic stiffness after TEVAR merits further investigation.
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Conflict of interest: The authors declare no conflicts of interest to disclose.
This work is partially funded by: ERC Starting Grant through the Project ISOBIO: Isogeometric Methods for Biomechanics [No. 259229]; Ministero dell’Istruzione,dell’Università e della Ricerca [Project no. 2010BFXRHS], iCardioCloud project by Cariplo Foundation [no. 2013-1779] and Lombardy Region [No. 42938382; No. 46554874].