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Introdução: O tratamento alternativo de Redução septal percutânea (RSP) em pacientes com cardiomiopatia hipertrófica obstrutiva é relativamente novo e há poucos trabalhos publicados sobre a evolução tardia. Objetivos: Avaliar nos pacientes com cardiomiopatia hipertrófica obstrutiva sintomáticos e refratários ao tratamento clínico, tratados com RSP, a sobrevida cardíaca e global, qualidade de vida, eventos maiores e as alterações encontradas no eletrocardiograma (ECG), ecocardiograma(ECO) e Holter 24h antes e na evolução tardia de até 15 anos. Método: Foram incluídos pacientes consecutivos que realizaram RSP no Instituto Dante Pazzanese de Cardiologia e no Hospital do Coração de Outubro de 1998 até junho de 2013. Todos os pacientes realizaram exame clínico, ECG e ECO, e a maioria Holter 24h e responderam o questionário DASI antes e pós-RSP. Os dados qualitativos foram descritos em frequências absolutas e relativas e os quantitativos resumidos em médias ± desvios padrão. Para as variáveis quantitativas foram utilizados modelos ANOVA com medidas repetidas, seguidos pelo método de comparações múltiplas de Bonferroni. O nível de significância de 0,05 foi aceito. Resultados: Dos 56 pacientes incluidos, 28 (50%) eram homens, a idade média foi 53,2 ±15,5 anos sendo 2 crianças e 11 (19,6%) tinham coronariopatia. A maioria estava em classe funcional III-IV, o gradiente médio basal por ECO foi 92,8 ± 3,3 mmHg, a espessura do septo 23,9 ± 0,6 e 62,5% tinha insuficiência mitral (IM) moderada. Durante a internação 1 (1,7%)paciente implantou marcapasso. Durante o seguimento de 7,4 ± 4 anos ocorreram 3 implantes de CDI, 2 por prevenção secundaria e 1 marcapasso, 1 nova RSP, 3 cirurgias de miectomias e houve 7 (12,5%) óbitos, apenas 2 de causa cardíaca. O tempo médio de sobrevida, estimado pelo método de Kaplan Meier foi de 13,3 anos (IC95% 12,2 a 14,5 anos), com expectativa de sobrevida de 96,4% em 1 ano, 87,7% em 5 anos e 81,0% a os 12 anos pós-RSP. Houve melhora significativa na qualidade de vida pelo questionário DASI e na classe funcional da NYHA que passou de 3,6 ± 0,5 para 1,2 ± 0,5 no pós-RSP. Na última avaliação do ECO o gradiente 9,37 ± 6,7 mmHg, o septo 12,87 ± 0,98 mm e a IM foi discreta em 90% todos com p < 0,001. Das variáveis analisadas somente o gradiente no estresse, p=0,039 e a massa p=0,024 foram associados a pior prognóstico. Conclusões: A redução septal percutânea mostrou, na evolução tardia com 100% de seguimento, ser uma técnica segura, eficaz em manter os benefícios tardiamente com baixa mortalidade, oferecendo melhora significativa da classe funcional e da qualidade de vida para os pacientes. / Introduction: Percutaneous septal Reduction (PSR) is a relatively new alternative treatment in patients with obstructive hypertrophic cardiomyopathy and there are few published studies on late evolution. Objectives: Evaluate in symptomatic patients with hypertrophic obstructive cardiomyopathy refractory to medical treatment and who underwent PSR, cardiac and overall survival, quality of life, major events and changes found on the electrocardiogram (ECG), echocardiography (ECHO) and Holter 24h before and after PSR during an evolution up to 15 years. Method: Consecutive patients who were submitted to RSP in Dante Pazzanese Institute of Cardiology and Heart Hospital from October 1998 were included. All patients went through clinical, ECG and ECHO examination, and nearly all answered DASI questionnaire, 24-hour Holter monitoring before and after PSR. Qualitative data were described as absolute and relative frequencies and quantitative summarized as means ± standard deviations. ANOVA models were used for quantitative variables with repeated measures, followed by Bonferroni method for multiple comparison. Significance level of 0.05 was accepted. Results: From 56 patients included, 28 (50%) were men , the mean age was 53.2 ± 15.5 years with 2 children and 11 (19.6%) had coronary artery disease . Most were in functional class III - IV from NYHA, the mean baseline ECO gradient was 92.8 ± 3.3 mmHg, the septal thickness 23.9 ± 0.6mm and 62.5 % had moderate mitral regurgitation (MR). During hospitalization 1 (1.7%) patient required permanent pacemaker. During follow-up of 7.4 ± 4 years, 3 patient required ICD implantation, 2 (for secondary prevention), 1 permanent pacemaker, 1 new RSP, 3 myectomy surgery. There were 7 (12.5%) deaths but only 2 of cardiac causes. The median survival time estimated by the Kaplan Meier was 13.3 years (95% CI 12.2 to 14.5 years), with expected survival of 96.4% at 1 year, 87.7% at 5 years and 81.0% at 12 years post-PSR. Significant improvement was seen in quality of life inferred by DASI questionnaire answers and NYHA functional class from 3.6 ± 0.5 to 1.2 ± 0.5. In last evaluation we found statistical significant reduction in ECO gradient 9.37 ± 6.7 mmHg, septum thikness 12.87 ± 0.98 mm and MR was mild in 90 % of patients. Of the variables analyzed only stress gradient (p = 0.039) and mass (p = 0.024) were associated with worse prognosis. Conclusions: The results of this study suggest that percutaneous septal reduction in late evolution with no loses in follow-up, is a safe technique, effective in reducing ventricular gradient and preserving the benefits in long-term evolution with low mortality, offering significant improvement in functional class and quality of life for patients.

Left ventricular (LV) volumes and ejection fraction (EF) are important predictors of cardiac morbidity and mortality. LV volumes provide valuable prognostic information which isparticularly useful in the selection of therapy or determination of the optimal time for surgery. Two-dimensional (2D) echocardiography is the most widely used non-invasive method forassessment of cardiac function, 2D echocardiography has however several limitations inmeasuring LV volumes and EF since the formulas for quantifications are based on geometricalassumptions. Three-dimensional (3D) echocardiography has been available for almost twodecades, although the use of this modality has not gained wide spread acceptance. 3D echocardiography can overcome the above mentioned limitation in LV volume and EF evaluation since it is not based on geometrical assumption. 3D echocardiography has been shownin several studies to be more accurate and reproducible with low inter- and intraobservervariability in comparison to 2D echocardiography regarding the measurements of LV volumesand EF. The overall aim of the thesis was to evaluate the feasibility and accuracy of 3D echocardiography based-methods in the clinical context. In Study I the feasibility of 3D echocardiography was investigated for determination of LV volumes and EF using parasternal, apical and subcostal approaches. The study demonstrated that the apical 3D echocardiography view offers superior visualization. Study II tested the possibility of creating flow-volume loops to differentiate patients with valvular abnormalities from normal subjects. There were significant differences in the pattern from flow-volume loops clearly separating the groups. In Study III the visual estimation, “eyeballing” of EF was evaluated with two- and tri-plane echocardiography in comparison to quantitative 3D echocardiography. The study confirmed that an experienced echocardiographer can, with a high level of agreement estimate EF both with two- and tri-plane echocardiography. Study IV exposed the high accuracy of stroke volume and cardiac output determination using a3D biplane technique by planimetrically tracing the left ventricular outflow tract and indicating that an assumption of circular left ventricular outflow tract is not reliable. In Study V, two 3D echocardiography modalities, single-beat and four-beat ECG-gated 3D echocardiography were evaluated in patients having sinus rhythm and atrial fibrillation. Thesingle-beat technique showed significantly lower inter-and intraobserver variability in LV volumes and EF measurements in patients having atrial fibrillation in comparison to four-beat ECG-gated acquisition due to absence of stitching artifact. All studies demonstrated good results suggesting 3D echocardiography to be a feasible andaccurate method in daily clinical settings. / degree of Medical DoctorQC 20100629

Echocardiography is a well established technique when evaluating the size and function of the heart. One of the most common ways to measure the size of the right ventricle (RV) is to measure the RV outflow tract 1(RVOT1). Several ways to measure RVOT1 are described in the literature.These ways were compared with echocardiography on 27 healthy subjects.The result showed significant differences in RVOT1, depending on the way it was measured, concluding that the same site, method and body positionshould be used when comparing RVOT1 in the same subject over time.One parameter to evaluate the RV diastolic function (RVDF) is to measure the RV isovolumetric relaxation time (RV-IVRT), a sensitive marker ofRV dysfunction. There are different ways to measure this. In this thesis two ways of measuring RV-IVRT and their time intervals were compared in 20 patients examined with echocardiography. There was a significant difference between the two methods indicating that they are not measuring the same interval.Another way to assess the RVDF is to measure the maximal early diastolicvelocity (MDV) in the long-axis direction. MDV can be measured bydifferent methods, hence 29 patients were examined and MDV was measured according to two methods. There was a good correlation but a poor agreement between the two methods meaning that reference values cannot be used interchangeably.Takotsubo cardiomyopathy is characterized by apical wall motion abnormalities without coronary stenosis. The pathology of this condition remains unclear. To evaluate biventricular changes in systolic long-axisfunction and diastolic parameters in the acute phase and after recovery, 13 patients were included and examined with echocardiography at admission and after recovery. The results showed significant biventricular improvementof systolic long-axis function while most diastolic parameters remainedunchanged.

Introdução: O tratamento alternativo de Redução septal percutânea (RSP) em pacientes com cardiomiopatia hipertrófica obstrutiva é relativamente novo e há poucos trabalhos publicados sobre a evolução tardia. Objetivos: Avaliar nos pacientes com cardiomiopatia hipertrófica obstrutiva sintomáticos e refratários ao tratamento clínico, tratados com RSP, a sobrevida cardíaca e global, qualidade de vida, eventos maiores e as alterações encontradas no eletrocardiograma (ECG), ecocardiograma(ECO) e Holter 24h antes e na evolução tardia de até 15 anos. Método: Foram incluídos pacientes consecutivos que realizaram RSP no Instituto Dante Pazzanese de Cardiologia e no Hospital do Coração de Outubro de 1998 até junho de 2013. Todos os pacientes realizaram exame clínico, ECG e ECO, e a maioria Holter 24h e responderam o questionário DASI antes e pós-RSP. Os dados qualitativos foram descritos em frequências absolutas e relativas e os quantitativos resumidos em médias ± desvios padrão. Para as variáveis quantitativas foram utilizados modelos ANOVA com medidas repetidas, seguidos pelo método de comparações múltiplas de Bonferroni. O nível de significância de 0,05 foi aceito. Resultados: Dos 56 pacientes incluidos, 28 (50%) eram homens, a idade média foi 53,2 ±15,5 anos sendo 2 crianças e 11 (19,6%) tinham coronariopatia. A maioria estava em classe funcional III-IV, o gradiente médio basal por ECO foi 92,8 ± 3,3 mmHg, a espessura do septo 23,9 ± 0,6 e 62,5% tinha insuficiência mitral (IM) moderada. Durante a internação 1 (1,7%)paciente implantou marcapasso. Durante o seguimento de 7,4 ± 4 anos ocorreram 3 implantes de CDI, 2 por prevenção secundaria e 1 marcapasso, 1 nova RSP, 3 cirurgias de miectomias e houve 7 (12,5%) óbitos, apenas 2 de causa cardíaca. O tempo médio de sobrevida, estimado pelo método de Kaplan Meier foi de 13,3 anos (IC95% 12,2 a 14,5 anos), com expectativa de sobrevida de 96,4% em 1 ano, 87,7% em 5 anos e 81,0% a os 12 anos pós-RSP. Houve melhora significativa na qualidade de vida pelo questionário DASI e na classe funcional da NYHA que passou de 3,6 ± 0,5 para 1,2 ± 0,5 no pós-RSP. Na última avaliação do ECO o gradiente 9,37 ± 6,7 mmHg, o septo 12,87 ± 0,98 mm e a IM foi discreta em 90% todos com p < 0,001. Das variáveis analisadas somente o gradiente no estresse, p=0,039 e a massa p=0,024 foram associados a pior prognóstico. Conclusões: A redução septal percutânea mostrou, na evolução tardia com 100% de seguimento, ser uma técnica segura, eficaz em manter os benefícios tardiamente com baixa mortalidade, oferecendo melhora significativa da classe funcional e da qualidade de vida para os pacientes. / Introduction: Percutaneous septal Reduction (PSR) is a relatively new alternative treatment in patients with obstructive hypertrophic cardiomyopathy and there are few published studies on late evolution. Objectives: Evaluate in symptomatic patients with hypertrophic obstructive cardiomyopathy refractory to medical treatment and who underwent PSR, cardiac and overall survival, quality of life, major events and changes found on the electrocardiogram (ECG), echocardiography (ECHO) and Holter 24h before and after PSR during an evolution up to 15 years. Method: Consecutive patients who were submitted to RSP in Dante Pazzanese Institute of Cardiology and Heart Hospital from October 1998 were included. All patients went through clinical, ECG and ECHO examination, and nearly all answered DASI questionnaire, 24-hour Holter monitoring before and after PSR. Qualitative data were described as absolute and relative frequencies and quantitative summarized as means ± standard deviations. ANOVA models were used for quantitative variables with repeated measures, followed by Bonferroni method for multiple comparison. Significance level of 0.05 was accepted. Results: From 56 patients included, 28 (50%) were men , the mean age was 53.2 ± 15.5 years with 2 children and 11 (19.6%) had coronary artery disease . Most were in functional class III - IV from NYHA, the mean baseline ECO gradient was 92.8 ± 3.3 mmHg, the septal thickness 23.9 ± 0.6mm and 62.5 % had moderate mitral regurgitation (MR). During hospitalization 1 (1.7%) patient required permanent pacemaker. During follow-up of 7.4 ± 4 years, 3 patient required ICD implantation, 2 (for secondary prevention), 1 permanent pacemaker, 1 new RSP, 3 myectomy surgery. There were 7 (12.5%) deaths but only 2 of cardiac causes. The median survival time estimated by the Kaplan Meier was 13.3 years (95% CI 12.2 to 14.5 years), with expected survival of 96.4% at 1 year, 87.7% at 5 years and 81.0% at 12 years post-PSR. Significant improvement was seen in quality of life inferred by DASI questionnaire answers and NYHA functional class from 3.6 ± 0.5 to 1.2 ± 0.5. In last evaluation we found statistical significant reduction in ECO gradient 9.37 ± 6.7 mmHg, septum thikness 12.87 ± 0.98 mm and MR was mild in 90 % of patients. Of the variables analyzed only stress gradient (p = 0.039) and mass (p = 0.024) were associated with worse prognosis. Conclusions: The results of this study suggest that percutaneous septal reduction in late evolution with no loses in follow-up, is a safe technique, effective in reducing ventricular gradient and preserving the benefits in long-term evolution with low mortality, offering significant improvement in functional class and quality of life for patients.

(1) Background: Hemodynamic assessment of prosthetic heart valves using conventional 2D transthoracic Echocardiography-Doppler (2D-TTE) has limitations. Of those, left ventricular outflow tract (LVOT) area measurement is one of the major limitations of the continuity equation, which assumes a circular LVOT. (2) Methods: This study comprised 258 patients with severe aortic stenosis (AS), who were treated with the ACURATE neo2. The LVOT area and its dependent Dopplerderived parameters, including effective orifice area (EOA) and stroke volume (SV), in addition to their indexed values, were calculated from post-TAVI 2D-TTE. In addition, the 3D-LVOT area from pre-procedural MDCT scans was obtained and used to calculate corrected Doppler-derived parameters. The incidence rates of prosthesis patient mismatch (PPM) were compared between the 2D-TTE and MDCT-based methods (3) Results: The main results show that the 2D-TTE measured LVOT is significantly smaller than 3D-MDCT (350.4 62.04 mm2 vs. 405.22 81.32 mm2) (95% Credible interval (CrI) of differences: 55.15, 36.09), which resulted in smaller EOA (2.25 0.59 vs. 2.58 0.63 cm2) (Beta = 0.642 (95%CrI of differences: 0.85, 0.43), and lower SV (73.88 21.41 vs. 84.47 22.66 mL), (Beta = 7.29 (95% CrI: 14.45, 0.14)), respectively. PPM incidence appears more frequent with 2D-TTE- than 3D-MDCT-corrected measurements (based on the EOAi) 8.52% vs. 2.32%, respectively. In addition, significant differences regarding the EOA among the three valve sizes (S, M and L) were seen only with the MDCT, but not on 2D-TTE. (4) Conclusions: The corrected continuity equation by combining the 3D-LVOT area from MDCT with the TTE Doppler parameters might provide a more accurate assessment of hemodynamic parameters and PPM diagnosis in patients treated with TAVI. The ACURATE neo2 THV has a large EOA and low incidence of PPM using the 3D-corrected LVOT area than on 2D-TTE. These findings need further confirmation on long-term follow-up and in other studies.

Ventricular premature beats are ectopic changes in the ECG signal. Detection of ventricular extrasystoles on 12leads ECG was created in MATLAB. At first my work involves whether the ventricular premature beats comes from the right or the left ventricle. Another algorithm evaluates the incidence outflow tract of the chamber. If the previous algorithm shows signs of indecision, another algorithm is used for detection of ventricular extrasystoles at another location in the left ventricle. The last step is to narrow the area of detection which makes it easier to find the place of origin.

réalisé en cotutelle avec le Dr. Marie Kmita et Dr. Marco Horb / Chez l’humain, les maladies congénitales cardiaques (MCC) sont présentes chez 3-4% des nouveaux nés et sont une cause importante de mortalité infantile et de morbidité dans le monde. La majorité des MCCs implique les valves et les septums, qui proviennent des cellules endocardiques. Les valves aortiques bicuspides (VAB) sont la MCC la plus fréquente chez l’humain, avec un taux estimé de 1-2% dans la population. Cependant, les gènes et les mécanismes moléculaires qui causent cette malformation demeurent obscures. Le facteur de transcription GATA5 est exprimé dans les cellules et les coussins endocardiques de façon transitoire durant la septation et la formation des compartiments cardiaques. Chez le poisson zèbre, des mutations dans le gène Gata5 causent des malformations cardiaques sévères incluant l’absence de cellules endocardiques. In vitro, l’inhibition de Gata5 bloque la différentiation endocardique. Ces études suggéraient donc un rôle important de GATA5 dans la formation du cœur. Dans le cadre de ce projet de doctorat, nous avons analysé le rôle de GATA5 dans le développement du cœur en produisant des lignées de souris chez lesquelles le gène Gata5 était inactif soit dans toutes les cellules ou uniquement dans les cellules endocardiques. Les souris possédant 2 allèles mutées du gène Gata5 étaient viables mais plus de 26% des souris Gata5-/- ont développé des VABs. Par ailleurs, une incidence similaire de VABs a été obtenue chez les souris ayant une délétion spécifique de Gata5 des cellules endocardiques, obtenue en croisant les souris Gata5WT/Flox avec les souris transgéniques Tie2-Cre. Sur le plan mécanistique, une réduction significative de JAG1, un corécepteur pour Notch1, ainsi qu’une augmentation marquée de Rbj un répresseur de cette voie, ont été détectés chez les souris Gata5-/- et Tie2- cre+;Gata5Flox/Flox, suggérant qu’une dérégulation de la voie Notch dans les cellules endocardiques puisse être la cause des VABs. Ces résultats démontrent l’importance de GATA5 pour le développement endocardique et la formation de la valve aortique. De plus, ils identifient GATA5 comme gène candidat de MCCs chez l’humain. Environ 12-14% des MCCs sont causés par le développement anormal de la voie de chasse, menant aux malformations telles que la transposition des grandes artères, la tétralogie de Fallot ou le syndrome du ventricule droit à double issue. Des mutations dans Gata4 et Gata6 sont associés à des défauts de la voie de chasse, dans plusieurs espèces incluant l’humain. Nous avons examiné si GATA5 interagit avec GATA4 ou GATA6 dans le développement de la voie de chasse. Alors que les souris hétérozygotes pour Gata5, Gata4 ou Gata6 ont des défauts cardiaques subtiles et sont viables, les embryons Gata4+/-Gata5+/- et Gata5+/-Gata6+/- démontrent une létalité embryonnaire et périnatale due à des défauts cardiaques, tel qu’un ventricule droit à double issue et des défauts de septation ventriculaire. Ces résultats indiquent l'importance des interactions génétiques entre GATA5 et les autres facteurs GATA pour la rotation et l’alignement de la voie de chasse au cours du développement cardiaque et soulèvent la possibilité que des changements subtiles de l'activité de 2 facteurs GATA puissent mener à des MCCs chez l'humain. / Congenital heart defect (CHD) in humans occur in 3-4% of live birth and is a major cause of infant mortality and morbidity in the world. The majority of CHD involves the valves and septa, which originate from endocardial cells. Bicuspid aortic valve (BAV) is the most common CHD in humans with an estimated rate of 1-2% in the population. However, very few genes have been linked to this defect and the mechanisms underlying BAV formation remain undefined. GATA5, a member of the GATA family of transcription factors, is expressed in a spatial and temporal manner in the developing heart where it is predominantly found in endocardial cells and endocardial cushions (ECs) of the outflow tract (OFT) and atrioventricular canal between E9.5-E12.5 in the mouse. Mutations in the Gata5 gene in zebrafish (faust mutants) cause cardia bifida and lead to endocardial cell depletion. In vitro studies using antisense mRNA against Gata5 revealed a critical role for this gene in differentiation of endocardial cells. In the context of the present doctoral research project, we investigated the role of GATA5 in mammalian heart development by generating a mouse line with a null Gata5 allele. Gata5 null mice are viable but over 26% of them developed BAVs. Endocardial specific deletion of Gata5 obtained by crossing mice with floxed (Flox) Gata5 alleles with Tie2-cre transgenic mice resulted in a similar incidence of BAVs. RNA profiling revealed that Jag-1, a co-receptor for Notch1, is significantly downregulated in both Gata5 null and Tie2-cre+;Gata5Flox/Flox mice, suggesting that disruption of Notch signaling in endocardial cells may be the underlying mechanism of disease. These findings reveal an important function for GATA5 in endocardial cell development and aortic valve formation and identify GATA5 as an important candidate CHD causing gene. Abnormal development of the OFT accounts for about 12-14% of all CHDs, leading to malformations such as persistent truncus arteriosus (PTA), tetralogy of Fallot (TOF), double outlet right ventricle (DORV) and transposition of the great arteries (TGA). Both GATA4 and GATA6 play important role in OFT development. We tested whether GATA5 might interact genetically with GATA4 and GATA6 for proper heart morphogenesis. We found that, whereas mice lacking a single copy of Gata5, Gata4 or Gata6 have subtle cardiac defects, the Gata4+/-Gata5+/- and Gata5+/-Gata6+/- mutant embryos show embryonic and perinatal lethality due to severe heart defects, including double outlet right ventricle and ventricular septal defects. These findings reveal the importance of genetic interactions between GATA5 and the other cardiac GATA factors in the normal rotation and patterning of the OFT during heart development in vivo. The results raise the possibility that subtle alterations in the level or activity of 2 cardiac GATA factors might lead to congenital heart disease in human.

Chez l’humain, les maladies congénitales cardiaques (MCC) sont présentes chez 3-4% des nouveaux nés et sont une cause importante de mortalité infantile et de morbidité dans le monde. La majorité des MCCs implique les valves et les septums, qui proviennent des cellules endocardiques. Les valves aortiques bicuspides (VAB) sont la MCC la plus fréquente chez l’humain, avec un taux estimé de 1-2% dans la population. Cependant, les gènes et les mécanismes moléculaires qui causent cette malformation demeurent obscures. Le facteur de transcription GATA5 est exprimé dans les cellules et les coussins endocardiques de façon transitoire durant la septation et la formation des compartiments cardiaques. Chez le poisson zèbre, des mutations dans le gène Gata5 causent des malformations cardiaques sévères incluant l’absence de cellules endocardiques. In vitro, l’inhibition de Gata5 bloque la différentiation endocardique. Ces études suggéraient donc un rôle important de GATA5 dans la formation du cœur. Dans le cadre de ce projet de doctorat, nous avons analysé le rôle de GATA5 dans le développement du cœur en produisant des lignées de souris chez lesquelles le gène Gata5 était inactif soit dans toutes les cellules ou uniquement dans les cellules endocardiques. Les souris possédant 2 allèles mutées du gène Gata5 étaient viables mais plus de 26% des souris Gata5-/- ont développé des VABs. Par ailleurs, une incidence similaire de VABs a été obtenue chez les souris ayant une délétion spécifique de Gata5 des cellules endocardiques, obtenue en croisant les souris Gata5WT/Flox avec les souris transgéniques Tie2-Cre. Sur le plan mécanistique, une réduction significative de JAG1, un corécepteur pour Notch1, ainsi qu’une augmentation marquée de Rbj un répresseur de cette voie, ont été détectés chez les souris Gata5-/- et Tie2- cre+;Gata5Flox/Flox, suggérant qu’une dérégulation de la voie Notch dans les cellules endocardiques puisse être la cause des VABs. Ces résultats démontrent l’importance de GATA5 pour le développement endocardique et la formation de la valve aortique. De plus, ils identifient GATA5 comme gène candidat de MCCs chez l’humain. Environ 12-14% des MCCs sont causés par le développement anormal de la voie de chasse, menant aux malformations telles que la transposition des grandes artères, la tétralogie de Fallot ou le syndrome du ventricule droit à double issue. Des mutations dans Gata4 et Gata6 sont associés à des défauts de la voie de chasse, dans plusieurs espèces incluant l’humain. Nous avons examiné si GATA5 interagit avec GATA4 ou GATA6 dans le développement de la voie de chasse. Alors que les souris hétérozygotes pour Gata5, Gata4 ou Gata6 ont des défauts cardiaques subtiles et sont viables, les embryons Gata4+/-Gata5+/- et Gata5+/-Gata6+/- démontrent une létalité embryonnaire et périnatale due à des défauts cardiaques, tel qu’un ventricule droit à double issue et des défauts de septation ventriculaire. Ces résultats indiquent l'importance des interactions génétiques entre GATA5 et les autres facteurs GATA pour la rotation et l’alignement de la voie de chasse au cours du développement cardiaque et soulèvent la possibilité que des changements subtiles de l'activité de 2 facteurs GATA puissent mener à des MCCs chez l'humain. / Congenital heart defect (CHD) in humans occur in 3-4% of live birth and is a major cause of infant mortality and morbidity in the world. The majority of CHD involves the valves and septa, which originate from endocardial cells. Bicuspid aortic valve (BAV) is the most common CHD in humans with an estimated rate of 1-2% in the population. However, very few genes have been linked to this defect and the mechanisms underlying BAV formation remain undefined. GATA5, a member of the GATA family of transcription factors, is expressed in a spatial and temporal manner in the developing heart where it is predominantly found in endocardial cells and endocardial cushions (ECs) of the outflow tract (OFT) and atrioventricular canal between E9.5-E12.5 in the mouse. Mutations in the Gata5 gene in zebrafish (faust mutants) cause cardia bifida and lead to endocardial cell depletion. In vitro studies using antisense mRNA against Gata5 revealed a critical role for this gene in differentiation of endocardial cells. In the context of the present doctoral research project, we investigated the role of GATA5 in mammalian heart development by generating a mouse line with a null Gata5 allele. Gata5 null mice are viable but over 26% of them developed BAVs. Endocardial specific deletion of Gata5 obtained by crossing mice with floxed (Flox) Gata5 alleles with Tie2-cre transgenic mice resulted in a similar incidence of BAVs. RNA profiling revealed that Jag-1, a co-receptor for Notch1, is significantly downregulated in both Gata5 null and Tie2-cre+;Gata5Flox/Flox mice, suggesting that disruption of Notch signaling in endocardial cells may be the underlying mechanism of disease. These findings reveal an important function for GATA5 in endocardial cell development and aortic valve formation and identify GATA5 as an important candidate CHD causing gene. Abnormal development of the OFT accounts for about 12-14% of all CHDs, leading to malformations such as persistent truncus arteriosus (PTA), tetralogy of Fallot (TOF), double outlet right ventricle (DORV) and transposition of the great arteries (TGA). Both GATA4 and GATA6 play important role in OFT development. We tested whether GATA5 might interact genetically with GATA4 and GATA6 for proper heart morphogenesis. We found that, whereas mice lacking a single copy of Gata5, Gata4 or Gata6 have subtle cardiac defects, the Gata4+/-Gata5+/- and Gata5+/-Gata6+/- mutant embryos show embryonic and perinatal lethality due to severe heart defects, including double outlet right ventricle and ventricular septal defects. These findings reveal the importance of genetic interactions between GATA5 and the other cardiac GATA factors in the normal rotation and patterning of the OFT during heart development in vivo. The results raise the possibility that subtle alterations in the level or activity of 2 cardiac GATA factors might lead to congenital heart disease in human. / réalisé en cotutelle avec le Dr. Marie Kmita et Dr. Marco Horb

L’obstruction de la chambre de chasse du ventricule droit (OCCVD) chez les adultes subissant une chirurgie cardiaque est un diagnostic rarement décrit dans la littérature. Dans le cadre de cette maîtrise, plusieurs études ont été réalisées afin de répondre aux questions suivantes qui sont importantes cliniquement : Quelle est la prévalence de l’OCCVD en chirurgie cardiaque adulte? Et quelle est sa prévalence dans une population adulte de chirurgie cardiaque sous surveillance hémodynamique constante avec un cathéter pulmonaire capable de mesure le gradient de pression de la chambre de chasse du ventricule droit? D’abord, une revue de littérature sur l’OCCVD a été réalisée en faisant une recherche systématique avec des mots-clés dans la base de données MEDLINE dans PubMed. À partir de toutes les études décrivant l’OCCVD en chirurgie cardiaque adulte, une prévalence de 4 % a été calculée. L’étiologie la plus courante de ce phénomène était mécanique et associée à une compression extrinsèque. Par la suite, une étude rétrospective sur une base de données du centre hospitalier affilié au programme a démontré une corrélation positive entre la survenue d’une OCCVD et une détérioration clinique postopératoire. Un total de 295 patients de 67.2 ± 9.26 ans (79% male) avec des mesures d’OCCVD pré et post-circulation extracorporelle (CEC) ont été analysés. Une OCCVD avec un gradient ≥ 6 mmHg a été observée avant la CEC chez 89 patients [30,2 % (25,1 % - 35,6 %)] et après la CEC chez 129 patients [43,7 % (38,2 % - 49,4 %)]. Nous avons déterminé que l’OCCVD est une complication rare mais importante à étudier et à suspecter puisqu’elle peut être ciblée par des traitements selon son étiologie. / Right ventricular outflow tract obstruction (RVOTO) is a diagnosis rarely described in adult patients undergoing cardiac surgery. In order to write this Master’s thesis, studies were conducted to determine the prevalence of RVOTO in adult cardiac surgery patients, as well as the prevalence in a similar population with continuous monitoring of pressure gradient data across the right ventricular outflow tract using a pulmonary artery catheter. First, we reviewed the literature on RVOTO by performing a systematic keyword search in the MEDLINE database via PubMed. A prevalence of 4% was calculated by extrapolating the results of all the studies describing RVOTO in adult cardiac surgery. The most common etiology for this phenomenon was mechanical and subsequent to an extrinsic compression. Second, a retrospective study on a database from the university-affiliated hospital center showed a positive correlation between the development of RVOTO and a postoperative clinical decline. A total of 295 patients aged 67.2 ± 9.26 years old (79% male) with RVOTO data from before and after cardiopulmonary bypass (CPB) were analysed. A RVOTO with a gradient ≥ 6 mmHg was observed before CPB in 89 patients [30.2% (25.1% - 35.6%)] et after CPB in 129 patients [43.7 % (38.2 % - 49.4 %)]. We determined that RVOTO is a rare but important complication because it can be targeted with therapies according to its etiology.