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Dahou, Abdellaziz

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Dahou
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Abdellaziz
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Université Laval. Faculté de médecine
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  • Publication
    Accès libre
    Dobutamine stress echocardiography for management of low-flow, low-gradient aortic stenosis
    (Elsevier Biomedical, 2018-01-29) Dahou, Abdellaziz; Larose, Éric; Annabi, Mohamed Salah; Burwash, Ian G.; Touboul, Eden; Bergler-Klein, Jutta; Pibarot, Philippe; Enriquez-Sarano, Maurice; Clavel, Marie-Annick; Orwat, Stefan; Baumgartner, Helmut; Mascherbauer, Julia; Mundigler, Gerald; Cavalcante, João L.
    Background: Dobutamine stress echocardiography (DSE) is useful to differentiate true from pseudo severe aortic stenosis in patients with low left ventricular ejection fraction (LVEF), low-flow, low-gradient aortic stenosis (LF-LG AS). In the ACC/AHA guidelines, patients are considered having true-severe stenosis when the mean gradient (MG) is ≥40mmHg with an aortic valve area (AVA) ≤1cm2 during DSE. However these criteria have not been previously validated. The aim of this study was to assess the value of these criteria to predict the presence of true-severe AS and the occurrence of death in patients with LFLG AS. Methods: In the TOPAS (“True or Pseudo-Severe Aortic Stenosis”) study, 186 patients with low LVEF LF-LG AS were prospectively recruited and underwent DSE with measurement of the MG, AVA and projected AVA, an estimate of the AVA at a standardized normal flow rate (AVAProj). Severity of AS was independently corroborated by macroscopic evaluation of the valve at the time of valve replacement in 54 patients and by measurement of the aortic valve calcium by computed tomography in 25 patients and by both methods in 8. According to these assessments, 50/87 (57%) of the study cohort had true-severe stenosis. Results: Peak stress MG ≥40 mmHg, peak stress AVA ≤1cm2, and the combination of peak stress MG ≥40 mmHg and peak stress AVA≤1cm2 correctly classified AS severity in 48%, 60%, and 47% of patients, respectively, whereas AVAProj ≤1cm2 was better than all the previous markers (p<0.007) with 70% of correct classification. Among the subset of 88 patients managed conservatively (47% of cohort), 52 died during a follow-up of 2.8±2.5 years. After adjustment for age, sex, functional capacity, chronic kidney failure and peak stress LVEF, peak stress MG and AVA were not predictors of mortality in this subset. In contrast, AVAProj ≤1cm2 was a strong predictor of mortality under medical management (HR: 3.65; p=0.0003). Conclusion: In patients with low LVEF LF-LG AS, the DSE criteria of peak stress MG≥40 mmHg, or the composite of peak stress MG≥40 mmHg and peak stress AVA≤1cm2 proposed in the guidelines to identify true-severe AS and recommend valve replacement, have limited value to predict actual stenosis severity and outcomes. In contrast, AVAProj better distinguishes true from pseudo-severe aortic stenosis and is strongly associated with mortality in patients under conservative management.
  • Publication
    Restreint
    Association of aortic valve leaflet calcification on hemodynamic and clinical outcomes
    (Elsevier Biomedical, 2020-10-05) Zhang, Bin; Dahou, Abdellaziz; Clisson, Marine; Mahjoub, Haïfa; Côté, Nancy; Zenses, Anne-Sophie; Pibarot, Philippe; Clavel, Marie-Annick; Mathieu, Patrick; Salaun, Erwan
    BACKGROUND The prognostic value of aortic valve calcification (AVC) measured by using multidetector computed tomography imaging has been well validated in native aortic stenosis, and sex-specific thresholds have been proposed. However, few data are available regarding the impact of leaflet calcification on outcomes after biological aortic valve replacement (AVR). OBJECTIVES The goal of this study was to analyze the association of quantitative bioprosthetic leaflet AVC with hemodynamic and clinical outcomes, as well as its possible interaction with sex. METHODS From 2008 to 2010, a total of 204 patients were prospectively enrolled with a median of 7.0 years (interquartile range: 5.1 to 9.2 years) after biological surgical AVR. AVC measured by using the Agatston method was indexed to the cross-sectional area of aortic annulus measured by echocardiography to calculate the AVC density (AVCd). Presence of hemodynamic valve deterioration (HVD; increase in mean gradient [MG] $10 mm Hg and/or increase in transprosthetic regurgitation $1) was assessed by echocardiography in 137 patients at the 3-year follow-up. The primary clinical endpoint was mortality or aortic valve re-intervention. RESULTS There was no significant sex-related difference in the relationship between bioprosthetic AVCd and the progression of MG. Baseline AVCd showed an independent association with HVD at 3 years. During follow-up, there were 134 (65.7%) deaths (n ¼ 100) or valve re-interventions (n ¼ 47). AVCd $58 AU/cm2 was independently associated with an increased risk of mortality or aortic valve re-intervention (adjusted hazard ratio: 2.23; 95% confidence interval: 1.44 to 3.35; p < 0.001). The AVCd threshold combined with an MG progression threshold of 10 mm Hg amplified the stratification of patients at risk (log-rank, p < 0.001). The addition of AVCd threshold into the prediction model including traditional risk factors improved outcome prediction (net classification improvement: 0.25, p ¼ 0.04; likelihood ratio test, p < 0.001). CONCLUSIONS Aortic bioprosthetic leaflet calcification is strongly and independently associated with HVD and the risk of death or aortic valve re-intervention. As opposed to native aortic stenosis, there is no sex-related differences in the relationship between AVCd and hemodynamic or clinical outcomes.
  • Publication
    Accès libre
    Nouveaux marqueurs pronostiques dans la sténose aortique à bas débit
    (2017) Dahou, Abdellaziz; Beaudoin, Jonathan; Pibarot, Philippe; Clavel, Marie-Annick
    La sténose aortique (SA) est la valvulopathie la plus fréquente dans les pays industrialisés. La SA avec bas débit cardiaque n’est pas une condition rare. Environ 5-10% des patients ayant une SA sévère présentent un état de bas débit cardiaque avec fraction d’éjection ventriculaire gauche (FEVG) diminuée (< 50%; c.-à-d. bas débit classique), et environ 10-25% présentent une SA à bas débit (SABD) malgré la présence d’une FEVG préservée (> 50%; c.-à-d. bas débit paradoxal). La présence d’un faible débit cardiaque s’accompagne souvent d’un bas gradient avec une petite aire valvulaire aortique (AVA) ce qui peut fausser l’évaluation de la sévérité de la sténose et conduire à une mauvaise décision thérapeutique. Deux principaux défis se posent chez ces patients afin de guider le traitement : le premier est de différentier une SA vraiment sévère (SAVS) d’une SA pseudo-sévère (SAPS) et le deuxième est de quantifier avec précision les dommages myocardiques pour mieux stratifier le risque. Malheureusement, les paramètres traditionnels dérivés de l’échocardiographie de repos ou de stress qui sont utilisés pour évaluer la sévérité de la SA et la fonction cardiaque sont loin d’être optimaux. Par conséquent, la quantification de la sévérité de la maladie et la prise en charge thérapeutique peuvent être inappropriées dans une proportion non négligeable de ces patients. L’objectif général de ce projet de doctorat est de déterminer quels sont, parmi les facteurs échocardiographiques, électrocardiographiques, et sanguins ceux qui permettent de mieux préciser la sévérité de la SA et l’atteinte myocardique et prédire de façon indépendante la survenue de morbidité et mortalité. Le but ultime est d’améliorer les algorithmes de stratification du risque et de décision thérapeutique chez ces patients.
  • Publication
    Restreint
    Impact of AVR on LV remodeling and function in paradoxical low-flow, low-gradient aortic stenosis with preserved LVEF
    (Elsevier, 2016-11-09) Dahou, Abdellaziz; O'Connor, Kim; Larose, Éric; Rodés-Cabau, Josep; Ribeiro, Henrique Barbosa; Capoulade, Romain; Beaudoin, Jonathan; Pibarot, Philippe; Dumesnil, Jean G.; Clavel, Marie-Annick; Mathieu, Patrick
  • Publication
    Restreint
    Prosthesis-patient mismatch after aortic valve replacement
    (Springer, 2016-09-29) Dahou, Abdellaziz; Mahjoub, Haïfa; Pibarot, Philippe
    Prosthesis-patient mismatch (PPM) occurs when the effective orifice area (EOA) of a normally functioning prosthesis is too small in relation to the patient’s body size, resulting in abnormally high postoperative gradients. PPM is frequent following aortic valve replacement (AVR), and it is associated with increased risk of morbidity and mortality proportionally to its severity. Differential diagnosis between PPM and prosthetic valve stenosis is made by comparing the measured valve effective orifice area, by assessing the changes in valve area and gradient during follow-up and by evaluating leaflet morphology and mobility. Preventive strategies to avoid or minimize PPM should be implemented especially in the patients who are at high risk for severe PPM and in those who have vulnerability factors to PPM. Transcatheter AVR may be superior to surgical AVR for the prevention of PPM and associated adverse cardiac events, particularly in the subset of patients with a small (<21 mm) aortic annulus. In this article, we discuss the most updated data regarding the diagnosis, clinical impact, and prevention of PPM after AVR.
  • Publication
    Restreint
    Association between plasma lipoprotein levels and bioprosthetic valve structural degeneration
    (BMJ, 2016-07-04) Dahou, Abdellaziz; Bouchareb, Rihab; Arsenault, Benoit; Larose, Éric; Mahjoub, Haïfa; Boulanger, Marie-Chloé; Bossé, Yohan; Mahmut, Ablajan; Pibarot, Philippe; Després, Jean-Pierre; Nsaibia, Mohamed Jalloul; Mathieu, Patrick
    Introduction: Structural valve degeneration (SVD) leads to the failure of aortic valve bioprostheses. It is suspected that lipid-derived factors could play a role in SVD. We hypothesised that oxidised low-density lipoprotein (OxLDL), OxLDL/LDL, OxLDL/high-density lipoprotein (OxLDL/HDL) and proprotein convertase subtilisin/kexin 9 (PCSK9) may be associated with SVD. Methods: We included 199 patients who underwent an aortic valve replacement with a bioprosthesis and had an echocardiography follow-up to evaluate the function of the prosthesis. SVD was defined as an increase in mean transprosthetic gradient (=10 mm Hg) or a worsening of transprosthetic regurgitation (=1/3) during the follow-up. Results: After a mean follow-up of 8±3.5 years, 41(21%) patients developed SVD. The univariate predictors of SVD were LDL (p=0.03), apolipoprotein B (p=0.01), OxLDL (p=0.02), OxLDL/HDL (p=0.009) and LDL associated with small, dense particles (LDL-C<255Å) (p=0.02). In a model adjusted for covariates, only OxLDL/HDL (OR 1.49, 95%CI 1.08 to 2.07 per 10 units, p=0.01) remained associated with SVD. There was a significant interaction between OxLDL/HDL and PCSK9 on SVD (p=0.05). After adjustment, compared with patients with low OxLDL/HDL (median, <25.4) and low PCSK9 (median, <298 ng/mL) (referent), patients with both an elevated OxLDL/HDL ratio and PCSK9 had a higher risk of SVD (OR 2.93, 95% CI 1.02 to 9.29, p=0.04). Conclusions: OxLDL/HDL ratio is independently associated with SVD.
  • Publication
    Restreint
    Cardiovascular magnetic resonance to evaluate aortic regurgitation after transcatheter aortic valve replacement
    (Elsevier, 2016-08-09) Campelo-Parada, Francisco; Orwat, Stefan; Dahou, Abdellaziz; Hayek, Salim; Abdul-Jawad Altisent, Omar; Larose, Éric; Babaliaros, Vasilis; Rodés-Cabau, Josep; Le Ven, Florent; Ribeiro, Henrique Barbosa; Pasian, Sergio; Pibarot, Philippe; Clavel, Marie-Annick; Puri, Rishi; Lerakis, Stamatios A.; Baumgartner, Helmut
    Background: Residual aortic regurgitation (AR) following transcatheter aortic valve replacement (TAVR) is associated with greater mortality; yet, determining AR severity post-TAVR using Doppler echocardiography remains challenging. Cardiovascular magnetic resonance (CMR) is purported as a more accurate means of quantifying AR; however, no data exist regarding the prognostic value of AR as assessed by CMR post-TAVR. Objectives: This study sought to evaluate the effect of AR assessed with CMR on clinical outcomes post-TAVR. Methods We included 135 patients from 3 centers. AR was quantified using regurgitant fraction (RF) measured by phase-contrast velocity mapping CMR at a median of 40 days post-TAVR, and using Doppler echocardiography at a median of 6 days post-TAVR. Median follow-up was 26 months. Clinical outcomes included mortality and rehospitalization for heart failure. Results: Moderate-severe AR occurred in 17.1% and 12.8% of patients as measured by echocardiography and CMR, respectively. Higher RF post-TAVR was associated with increased mortality (hazard ratio: 1.18 for each 5% increase in RF [95% confidence interval: 1.08 to 1.30]; p < 0.001) and the combined endpoint of mortality and rehospitalization for heart failure (hazard ratio: 1.19 for each 5% increase in RF; 95% confidence interval: 1.15 to 1.23; p < 0.001). Prediction models yielded significant incremental predictive value; CMR performed a median of 40 days post-TAVR had a greater association with post-TAVR clinical events compared with early echocardiography (p < 0.01). RF =30% best predicted poorer clinical outcomes (p < 0.001 for either mortality or the combined endpoint of mortality and heart failure rehospitalization). Conclusions: Worse CMR-quantified AR was associated with increased mortality and poorer clinical outcomes following TAVR. Quantifying AR with CMR may identify patients with AR who could benefit from additional treatment measures.
  • Publication
    Restreint
    Autotaxin Derived From Lipoprotein(a) and Valve Interstitial Cells Promotes Inflammation and Mineralization of the Aortic Valve
    (American Heart Association, etc., 2015-08-25) Dahou, Abdellaziz; Bouchareb, Rihab; Arsenault, Benoit; Trahan, Sylvain; Marette, André.; Couture, Christian; Lépine, Jamie-Lee; Boulanger, Marie-Chloé; Bossé, Yohan; Mahmut, Ablajan; Pibarot, Philippe; Hadji, Fayez; Pagé, Sylvain; Scipione, Corey A.; Nsaibia, Mohamed Jalloul; Romagnuolo, Rocco; Laflamme, Marie-Hélène; Koschinsky, Marlys L.; Mathieu, Patrick
    Background—Mendelian randomization studies have highlighted that lipoprotein(a) [Lp(a)] was associated with calcific aortic valve disease (CAVD). Lp(a) transports oxidized phospholipids (OxPLs) with a high content in lysophosphatidylcholine (LPC). Autotaxin (ATX) transforms LPC into lysophosphatidic acid. We hypothesized that ATX-lysophosphatidic acid could promote inflammation/mineralization of the aortic valve. Methods and Results—We have documented the expression of ATX in control and mineralized aortic valves. By using different approaches we have also investigated the role of ATX- lysophosphatidic acid on the mineralization of isolated valves interstitial cells (VICs) and in a mouse model of CAVD. Enzyme specific ATX activity was elevated by 60% in mineralized aortic valves compared to control valves. Immunohistochemistry studies showed a high level of ATX in mineralized aortic valves, which co-localized with OxPL and apolipoprotein(a). We detected a high level of ATX activity in the Lp(a) fraction in circulation. Interaction between ATX and Lp(a) was confirmed by in situ proximity ligation assay. Moreover, we documented that VICs also expressed ATX in CAVD. We showed that ATX-lysophosphatidic acid promote the mineralization of the aortic valve through a NF-¿B/IL-6/BMP2 pathway. In LDLR-/-/ApoB100/100/IGFII mice, ATX is overexpressed and lysophosphatidic acid promotes a strong deposition of hydroxyapatite of calcium in aortic valve leaflets and accelerates the development of CAVD. Conclusions—ATX is transported in the aortic valve by Lp(a) and is also secreted by VICs. ATX-lysophosphatidic acid promotes inflammation and mineralization of the aortic valve and thus could represent novel therapeutic targets in CAVD.
  • Publication
    Restreint
    Downregulation of microRNA-126 contributes to the failing right ventricle in pulmonary arterial hypertension
    (American Heart Association, 2015-09-08) Dahou, Abdellaziz; Charbonneau, Éric; Provencher, Steeve; Thébault, Christophe; Ruffenach, Grégoire; Breuils-Bonnet, Sandra; Bonnet, Sébastien; Johnson, Ian; Perron, Jean; Paulin, Roxane; Tremblay, Ève; Wong, Ryan; Lajoie, Annie C.; Joubert, Philippe; Potus, François; Pibarot, Philippe; Michelakis, Evangelos D.; Graydon, Colin; Paradis, Renée; Nadeau, Valérie
    Background—Right ventricular (RV) failure is the most important factor of both morbidity and mortality in pulmonary arterial hypertension (PAH). However, the underlying mechanisms resulting in the failed RV in PAH remain unknown. There is growing evidence that angiogenesis and microRNAs are involved in PAH-associated RV failure. We hypothesized that microRNA-126 (miR-126) downregulation decreases microvessel density and promotes the transition from a compensated to a decompensated RV in PAH. Methods and Results—We studied RV free wall tissues from humans with normal RV (n=17), those with compensated RV hypertrophy (n=8), and patients with PAH with decompensated RV failure (n=14). Compared with RV tissues from patients with compensated RV hypertrophy, patients with decompensated RV failure had decreased miR-126 expression (quantitative reverse transcription–polymerase chain reaction; P<0.01) and capillary density (CD31+ immunofluorescence; P<0.001), whereas left ventricular tissues were not affected. miR-126 downregulation was associated with increased Sprouty-related EVH1 domain-containing protein 1 (SPRED-1), leading to decreased activation of RAF (phosphorylated RAF/RAF) and mitogen-activated protein kinase (MAPK); (phosphorylated MAPK/MAPK), thus inhibiting the vascular endothelial growth factor pathway. In vitro, Matrigel assay showed that miR-126 upregulation increased angiogenesis of primary cultured endothelial cells from patients with decompensated RV failure. Furthermore, in vivo miR-126 upregulation (mimic intravenous injection) improved cardiac vascular density and function of monocrotaline-induced PAH animals. Conclusions—RV failure in PAH is associated with a specific molecular signature within the RV, contributing to a decrease in RV vascular density and promoting the progression to RV failure. More importantly, miR-126 upregulation in the RV improves microvessel density and RV function in experimental PAH.
  • Publication
    Restreint
    Myocardial injury after transaortic versus transapical transcatheter aortic valve replacement
    (Little, Brown & Co.,, 2015-06-01) Campelo-Parada, Francisco; Dahou, Abdellaziz; Carrasco, José Luis; Dumont, Éric; Abdul-Jawad Altisent, Omar; Rodés-Cabau, Josep; Le Ven, Florent; DeLarochellière, Robert; Mohammadi, Siamak; Paradis, Jean-Michel; Amat Santos, Ignacio J.; Doyle, Daniel; Del Trigo, Maria; Urena Alcazar, Marina; Pibarot, Philippe; Allende, Ricardo; Puri, Rishi; Barbosa Ribeiro, Henrique
    Background : The release of cardiac biomarkers of myocardial injury after transcatheter aortic valve replacement (TAVR) is common, but no data exist on patients undergoing TAVR through a transaortic approach. We aimed to evaluate the incidence and prognostic significance of the increase in cardiac biomarkers in nontransfemoral TAVR candidates, comparing transaortic and transapical approaches. Methods : After excluding patients deemed suitable for transfemoral TAVR, 251 consecutive patients (transaortic, 45; transapical, 206) were prospectively evaluated. Creatine kinase–myocardial band and cardiac troponin T levels were measured at baseline and at 6, 12, 24, 48, and 72 hours after TAVR. Baseline and 6- to 12-month echocardiographic and clinical follow-up were performed. Results : After TAVR, cardiac troponin T increased above the upper normal values in all patients (peak value 0.64 µg/L [IQR, 0.39 to 1.03 µg/L]), whereas creatine kinase–myocardial band levels increased in 88% of patients (transaortic 51%, transapical 96%, p < 0.001; peak value 20.1 µg/L [interquartile range, 14.3 to 31.6 µg/L]). Compared with the transaortic approach, the transapical approach was associated with a greater rise in both cardiac biomarkers (p < 0.001 for both), and a lesser improvement in left ventricular ejection fraction (p = 0.058) and global longitudinal strain (p = 0.039) at 6- to 12-month follow-up. Greater increases of cardiac troponin T levels were independently associated with 30-day and 1-year overall and cardiovascular mortality (p < 0.001 for all). A 15-fold rise in cardiac troponin T levels was the optimal threshold for determining poorer outcomes (p < 0.001). Conclusions : Periprocedural TAVR-related myocardial injury in nontransfemoral candidates was demonstrated in all patients, but the transapical approach was associated with significantly greater myocardial injury compared with the transaortic approach. A higher degree of myocardial injury translated into reduced left ventricular function improvement and lower early and midterm survival rates.