ORIGINAL ARTICLE
European Journal of Cardio-Thoracic Surgery 46 (2014) e89–e93 doi:10.1093/ejcts/ezu358 Advance Access publication 18 September 2014
Comparison of ascending aortic cohesion between patients with bicuspid aortic valve stenosis and regurgitation Jaroslav Benedika,*, Daniel S. Dohlea, Daniel Wendta, Kevin Pilarczyka, Vivien Pricea, Fanar Mourada, Elizaveta Zykinaa, Ferdinand Stebnerb, Konstantinos Tsagakisa and Heinz Jakoba a b
Department of Thoracic and Cardiovascular Surgery, West-German Heart Center, University Hospital Essen, University of Duisburg Essen, Essen, Germany Department of Research on Learning and Instruction, Institute of Educational Science, Ruhr-University Bochum, Bochum, Germany
* Corresponding author. Department of Thoracic and Cardiovascular Surgery, West German Heart Center, University Hospital Essen, Hufelandstrasse 55, 45147 Essen, Germany. Tel: +49-201-72385578; fax: +49-201-7235451; e-mail: [email protected] ( J. Benedik). Received 13 April 2014; received in revised form 4 August 2014; accepted 7 August 2014
Abstract OBJECTIVES: A bicuspid aortic valve (BAV) is commonly associated with aortic wall abnormalities, including dilatation of the ascending aorta and increased potential for aortic dissection. We compared the mechanical properties of the aortic wall of BAV patients with aortic valve stenosis (AS) and regurgitation (AR) using a dissectometer, a device mimicking transverse aortic wall shear stress.
RESULTS: Patients with aortic regurgitation were significantly younger (48.2 ± 15.8 vs 64.7 ± 10.7, P < 0.001), and had a significantly thicker aortic wall (2.30 ± 0.49 mm vs 2.06 ± 0.35 mm, P = 0.029). Transoesophageal echocardiography diameters (annulus, aortic sinuses and sinotubular junction) were significantly larger in the AR group (27.3 ± 3.6 vs 25.5 ± 2.4, P = 0.008; 41.1 ± 7.7 vs 36.7 ± 8.0, P = 0.011; 37.6 ± 9.7 vs 33.8 ± 9.1, P = 0.049). The ascending aortic diameter did not differ (43.2 ± 10.6 vs 40.3 ± 9.1, P = 0.292). Patients with AR had significantly worse aortic cohesion, as measured by shear stress testing (P7: 97.2 ± 45.0 vs 145.5 ± 84.9, P = 0.015; P8: 2.00 ± 0.65 vs 3.82 ± 1.56, P < 0.001; P9: 2.96 ± 0.82 vs 4.98 ± 1.80, P < 0.001) compared with those with AS. CONCLUSIONS: We observed significantly worse aortic wall cohesion, a thicker aortic wall and a larger aortic root in patients presenting with bicuspid AR compared with patients with AS. These results suggest that bicuspid AR represents a different disease process with possible involvement of the ascending aorta, as demonstrated by dissectometer examination. Keywords: Aortic wall • Bicuspid aortic valve • Dissection • Aortic wall cohesion testing
INTRODUCTION A bicuspid aortic valve (BAV) is an aortic valve malformation that is often associated with aortic wall pathology [1]. It is not currently possible to predict future dilatation of the aorta or the risk of aortic dissection (AD) in patients with BAV. However, recent studies have identified aortic stenosis in patients with BAV acting as a trigger for post-stenotic dilatation, a potential risk factor for further aortic complications [2]. This type of aortic dilatation is probably combined with complete other aortic wall quality as these by patient with aortic bulbus dilatation and aortic valve regurgitation (AR) [3]. Histological examination of the ascending aorta of BAV patients regularly shows abnormalities of the media including fragmentation of elastin or accumulation of various deposits, leading to an alteration of the mechanical properties of the aortic wall [4]. Patients with AR become symptomatic at a younger age compared with those with bicuspid stenosis, which
can even be an incidental finding at aortic valve replacement in advanced age. The presence of a BAV is an independent risk factor for progressive aortic dilatation, aneurysm formation and dissection. It is for this reason that the recommendation for concomitant ascending aortic replacement during valve replacement surgery is stricter in BAV patients than in those with tricuspid valves [5]. Moreover, as there might be a link between aortic regurgitation and aortic pathology, one explanation of this missing disparity between tricuspid and bicuspid valves might be the high proportion of stenotic valves. This hypothesis is encouraged by another study of our group revealing impaired quality of the ascending aorta in patients with AR compared with those with AS [6]. Based on these results, we focused in the current study on comparing patients with a stenotic BAV with those presenting with an incompetent BAV by our recently introduced Dissectometer device.
© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ADULT CARDIAC
METHODS: Between March 2010 and February 2013, 85 consecutive patients with bicuspid aortic valve undergoing open aortic valve replacement at our institution were prospectively enrolled, presenting either with stenosis (Group 1, n = 58) or regurgitation (Group 2, n = 27). Aortic wall cohesion measured by the dissectometer (Parameters P7, P8 and P9), aortic diameters measured by transoesophageal echocardiography (TOE) and thickness of the wall were compared. One patient presenting with the Marfan syndrome was excluded from the study.
e90
J. Benedik et al. / European Journal of Cardio-Thoracic Surgery
MATERIALS AND METHODS Study design The study was approved by the Institutional Review Board and patients’ written informed consent was obtained. This single-centre, non-randomized study included 85 consecutive patients with BAV who underwent aortic valve replacement with or without other concomitant cardiac surgery at the West-German Heart Center Essen between March 2010 and February 2013. The study population of 85 patients was divided into two groups: 58 patients (Group 1) presented with bicuspid stenosis and 27 patients with bicuspid regurgitation (Group 2). One patient with Marfan syndrome was excluded from the study. Aortic diameters (aortic annulus, bulbus, sinotubular junction and ascending aortic dimensions) were assessed by intraoperative transoesophageal echocardiography (TOE). Patients with dilatation of the aortic root or ascending aorta scheduled for aortic replacement also underwent a computer tomography scan to aid with procedural planning.
Sample collection The operations were carried out through a median sternotomy with ascending aortic cannulation. After transverse aortotomy, a sample of the aortic wall was harvested from the edge of the aortic incision site (5 × 20 mm), as previously described, and was immediately placed in cold saline until the cohesion test was performed (within 2 h after surgery) [6, 7]. The aortic incision was closed in the usual manner without any resulting complications. Aortic wall thickness was measured immediately before cohesion testing, using a micrometer (Kometex B.V./Hogetex, Varsseveld, Netherlands).
Intraoperative echocardiography TOE was performed with a multiplane 2.9–6.7 MHz (6T-RS) phased-array probe (Vivid i, GE Healthcare, Milwaukee, WI, USA) prior to cardiopulmonary bypass in all patients. All aortic dimensions (diameter of the aortic annulus, aortic sinuses, sinotubular junction and ascending aorta) were measured.
Aortic wall cohesion testing Aortic wall cohesion testing was performed using the Dissectometer as previously described [7], and the results of the dissecting process were visualized as tensile strain curves (TSCs), which were subsequently converted into numerical parameters. P1, P2, P5 and P6 correspond to points on the curve. P1 (mm) is the beginning of the positive deviation—the point when the dissectometer registers the tension in the sample. P2 (mm) is the point of the dissection, and the power has a value of zero. P5 (N) is the first power maximum (at this point the power has decreased temporarily). After this point, the aortic wall sample is damaged irreversibly. P6 (N) represents the ‘dissection limit’ after which the power necessary to disrupt the aorta decreases. P3 (N mm−1) is the angle of the line between P1 and P5. This characteristic describes the elasticity of the aortic wall—the sharper the angle, the higher is the elasticity of the aorta. P4 (N mm−1) is the angle of the power decrease, which characterizes the cohesion of the
Figure 1: Tensile strain curve—the localization of the parameters P4, P6 and P7; mathematical formula for P8 and P9.
aortic wall. P7 (N mm) represents the area under the TSC that describes the total cohesion of the aorta. These seven parameters were used to mathematically derive the next two parameters, P8 and P9. P8 is described as the ‘dissection tendency’ (calculated as the maximal force divided by the downward angle) and P9 as the ‘dissection potential’ (calculated as the sum of P8 and the square root of P7 divided by 10). The parameters with the highest sensitivity and specificity for discriminating between histologically stable und unstable aortic wall identified in a previous study (P7, P8 and P9) were analysed in the present study (Fig. 1) [6, 7]. All cohesion tests were performed and analysed by one observer blinded to all patient data including aortic valve pathology.
Statistics Descriptive statistics are summarized for categorical variables as frequencies (%). Continuous variables are reported as mean ± standard deviation. The continual variables were compared using the Student t-test or Mann-Whitney U test. For categorical variables, Pearson’s χ 2 or Fisher’s exact tests were used. A P-value of
European Journal of Cardio-Thoracic Surgery 46 (2014) e89–e93 doi:10.1093/ejcts/ezu358 Advance Access publication 18 September 2014
Comparison of ascending aortic cohesion between patients with bicuspid aortic valve stenosis and regurgitation Jaroslav Benedika,*, Daniel S. Dohlea, Daniel Wendta, Kevin Pilarczyka, Vivien Pricea, Fanar Mourada, Elizaveta Zykinaa, Ferdinand Stebnerb, Konstantinos Tsagakisa and Heinz Jakoba a b
Department of Thoracic and Cardiovascular Surgery, West-German Heart Center, University Hospital Essen, University of Duisburg Essen, Essen, Germany Department of Research on Learning and Instruction, Institute of Educational Science, Ruhr-University Bochum, Bochum, Germany
* Corresponding author. Department of Thoracic and Cardiovascular Surgery, West German Heart Center, University Hospital Essen, Hufelandstrasse 55, 45147 Essen, Germany. Tel: +49-201-72385578; fax: +49-201-7235451; e-mail: [email protected] ( J. Benedik). Received 13 April 2014; received in revised form 4 August 2014; accepted 7 August 2014
Abstract OBJECTIVES: A bicuspid aortic valve (BAV) is commonly associated with aortic wall abnormalities, including dilatation of the ascending aorta and increased potential for aortic dissection. We compared the mechanical properties of the aortic wall of BAV patients with aortic valve stenosis (AS) and regurgitation (AR) using a dissectometer, a device mimicking transverse aortic wall shear stress.
RESULTS: Patients with aortic regurgitation were significantly younger (48.2 ± 15.8 vs 64.7 ± 10.7, P < 0.001), and had a significantly thicker aortic wall (2.30 ± 0.49 mm vs 2.06 ± 0.35 mm, P = 0.029). Transoesophageal echocardiography diameters (annulus, aortic sinuses and sinotubular junction) were significantly larger in the AR group (27.3 ± 3.6 vs 25.5 ± 2.4, P = 0.008; 41.1 ± 7.7 vs 36.7 ± 8.0, P = 0.011; 37.6 ± 9.7 vs 33.8 ± 9.1, P = 0.049). The ascending aortic diameter did not differ (43.2 ± 10.6 vs 40.3 ± 9.1, P = 0.292). Patients with AR had significantly worse aortic cohesion, as measured by shear stress testing (P7: 97.2 ± 45.0 vs 145.5 ± 84.9, P = 0.015; P8: 2.00 ± 0.65 vs 3.82 ± 1.56, P < 0.001; P9: 2.96 ± 0.82 vs 4.98 ± 1.80, P < 0.001) compared with those with AS. CONCLUSIONS: We observed significantly worse aortic wall cohesion, a thicker aortic wall and a larger aortic root in patients presenting with bicuspid AR compared with patients with AS. These results suggest that bicuspid AR represents a different disease process with possible involvement of the ascending aorta, as demonstrated by dissectometer examination. Keywords: Aortic wall • Bicuspid aortic valve • Dissection • Aortic wall cohesion testing
INTRODUCTION A bicuspid aortic valve (BAV) is an aortic valve malformation that is often associated with aortic wall pathology [1]. It is not currently possible to predict future dilatation of the aorta or the risk of aortic dissection (AD) in patients with BAV. However, recent studies have identified aortic stenosis in patients with BAV acting as a trigger for post-stenotic dilatation, a potential risk factor for further aortic complications [2]. This type of aortic dilatation is probably combined with complete other aortic wall quality as these by patient with aortic bulbus dilatation and aortic valve regurgitation (AR) [3]. Histological examination of the ascending aorta of BAV patients regularly shows abnormalities of the media including fragmentation of elastin or accumulation of various deposits, leading to an alteration of the mechanical properties of the aortic wall [4]. Patients with AR become symptomatic at a younger age compared with those with bicuspid stenosis, which
can even be an incidental finding at aortic valve replacement in advanced age. The presence of a BAV is an independent risk factor for progressive aortic dilatation, aneurysm formation and dissection. It is for this reason that the recommendation for concomitant ascending aortic replacement during valve replacement surgery is stricter in BAV patients than in those with tricuspid valves [5]. Moreover, as there might be a link between aortic regurgitation and aortic pathology, one explanation of this missing disparity between tricuspid and bicuspid valves might be the high proportion of stenotic valves. This hypothesis is encouraged by another study of our group revealing impaired quality of the ascending aorta in patients with AR compared with those with AS [6]. Based on these results, we focused in the current study on comparing patients with a stenotic BAV with those presenting with an incompetent BAV by our recently introduced Dissectometer device.
© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ADULT CARDIAC
METHODS: Between March 2010 and February 2013, 85 consecutive patients with bicuspid aortic valve undergoing open aortic valve replacement at our institution were prospectively enrolled, presenting either with stenosis (Group 1, n = 58) or regurgitation (Group 2, n = 27). Aortic wall cohesion measured by the dissectometer (Parameters P7, P8 and P9), aortic diameters measured by transoesophageal echocardiography (TOE) and thickness of the wall were compared. One patient presenting with the Marfan syndrome was excluded from the study.
e90
J. Benedik et al. / European Journal of Cardio-Thoracic Surgery
MATERIALS AND METHODS Study design The study was approved by the Institutional Review Board and patients’ written informed consent was obtained. This single-centre, non-randomized study included 85 consecutive patients with BAV who underwent aortic valve replacement with or without other concomitant cardiac surgery at the West-German Heart Center Essen between March 2010 and February 2013. The study population of 85 patients was divided into two groups: 58 patients (Group 1) presented with bicuspid stenosis and 27 patients with bicuspid regurgitation (Group 2). One patient with Marfan syndrome was excluded from the study. Aortic diameters (aortic annulus, bulbus, sinotubular junction and ascending aortic dimensions) were assessed by intraoperative transoesophageal echocardiography (TOE). Patients with dilatation of the aortic root or ascending aorta scheduled for aortic replacement also underwent a computer tomography scan to aid with procedural planning.
Sample collection The operations were carried out through a median sternotomy with ascending aortic cannulation. After transverse aortotomy, a sample of the aortic wall was harvested from the edge of the aortic incision site (5 × 20 mm), as previously described, and was immediately placed in cold saline until the cohesion test was performed (within 2 h after surgery) [6, 7]. The aortic incision was closed in the usual manner without any resulting complications. Aortic wall thickness was measured immediately before cohesion testing, using a micrometer (Kometex B.V./Hogetex, Varsseveld, Netherlands).
Intraoperative echocardiography TOE was performed with a multiplane 2.9–6.7 MHz (6T-RS) phased-array probe (Vivid i, GE Healthcare, Milwaukee, WI, USA) prior to cardiopulmonary bypass in all patients. All aortic dimensions (diameter of the aortic annulus, aortic sinuses, sinotubular junction and ascending aorta) were measured.
Aortic wall cohesion testing Aortic wall cohesion testing was performed using the Dissectometer as previously described [7], and the results of the dissecting process were visualized as tensile strain curves (TSCs), which were subsequently converted into numerical parameters. P1, P2, P5 and P6 correspond to points on the curve. P1 (mm) is the beginning of the positive deviation—the point when the dissectometer registers the tension in the sample. P2 (mm) is the point of the dissection, and the power has a value of zero. P5 (N) is the first power maximum (at this point the power has decreased temporarily). After this point, the aortic wall sample is damaged irreversibly. P6 (N) represents the ‘dissection limit’ after which the power necessary to disrupt the aorta decreases. P3 (N mm−1) is the angle of the line between P1 and P5. This characteristic describes the elasticity of the aortic wall—the sharper the angle, the higher is the elasticity of the aorta. P4 (N mm−1) is the angle of the power decrease, which characterizes the cohesion of the
Figure 1: Tensile strain curve—the localization of the parameters P4, P6 and P7; mathematical formula for P8 and P9.
aortic wall. P7 (N mm) represents the area under the TSC that describes the total cohesion of the aorta. These seven parameters were used to mathematically derive the next two parameters, P8 and P9. P8 is described as the ‘dissection tendency’ (calculated as the maximal force divided by the downward angle) and P9 as the ‘dissection potential’ (calculated as the sum of P8 and the square root of P7 divided by 10). The parameters with the highest sensitivity and specificity for discriminating between histologically stable und unstable aortic wall identified in a previous study (P7, P8 and P9) were analysed in the present study (Fig. 1) [6, 7]. All cohesion tests were performed and analysed by one observer blinded to all patient data including aortic valve pathology.
Statistics Descriptive statistics are summarized for categorical variables as frequencies (%). Continuous variables are reported as mean ± standard deviation. The continual variables were compared using the Student t-test or Mann-Whitney U test. For categorical variables, Pearson’s χ 2 or Fisher’s exact tests were used. A P-value of
