Fluidodinâmica Computacional na Avaliação do Risco Futuro de Aneurismas de Aorta Ascendente / Computational Fluid Dynamics to Assess the Future Risk of Ascending Aortic Aneurysms

Resumo Fundamentos Uma metodologia para identificação de pacientes portadores de aneurisma de aorta ascendente (AAAs) sob alto risco de remodelamento aórtico não está completamente definida. Objetivo Esta pesquisa objetiva caracterizar numericamente o fluxo sanguíneo aórtico, relacionando a distribuição do estresse mecânico resultante com o crescimento de AAAs. Métodos Estudo analítico, observacional, unicêntrico, em que um protocolo de fluidodinâmica computacional (CFD - Computacional Fluid Dynamics) foi aplicado a imagens de angiotomografia computadorizada (ATC) de aorta de pacientes portadores de AAAs. Duas ATC de aorta com pelo menos um ano de intervalo foram obtidas. Dados clínicos dos pacientes foram registrados e, a partir das imagens de ATC, foram gerados modelos tridimensionais. Foram realizados estudos do campo de velocidade e estruturas coerentes (vórtices) com o objetivo de relacioná-los ao crescimento ou não do aneurisma e, posteriormente, compará-los com os dados clínicos dos pacientes. O teste de Kolmogorov-Smirnov foi utilizado para avaliar a normalidade da amostra e o teste não-paramétrico Wilcoxon signed-rank foi aplicado para comparações de dados pareados entre os ângulos aórticos. A significância estatística foi fixada em 5%. Resultados Para o grupo que apresentou crescimento do aneurisma, a incidência do jato na parede aórtica gerou áreas de recirculação posterior ao jato, induzindo à formação de vórtices complexos, ocasionando um incremento na pressão média no endotélio aórtico. O grupo sem crescimento do aneurisma apresentou diminuição na pressão média. Conclusão Este estudo piloto mostrou que a CFD baseada em ATC pode, em um futuro próximo, ser uma ferramenta auxiliar na identificação dos padrões de fluxo associados ao processo de remodelamento de AAAs.

Abstract Background A methodology to identify patients with ascending aortic aneurysm (AsAA) under high risk for aortic growth is not completely defined Objetive This research seeks to numerically characterize the aortic blood flow by relating the resulting mechanical stress distribution with AsAA growth. Methods Analytical, observational, single-center study in which a computational fluid dynamics (CFD) protocol was applied to aortic computed tomography angiogram (CTA) images of patients with AsAA. Two CTA exams taken at a minimum interval of one year were obtained. From the CTA-gathered images, three-dimensional models were built, and clinical data were registered. Study of velocity field and coherent structures (vortices) was performed aiming to relate them to the presence or absence of aneurysm growth, as well as comparing them to the patients' clinical data. The Kolmogorov-Smirnov test was used to evaluate the normality of the distribution, and the non-parametric Wilcoxon signed-rank test, for non-normal distribution, was used to compare the paired data of the aortic angles. Statistical significance was set at 5%. Results The incident jet in the aortic wall generated recirculation areas in the posterior region of the jet, inducing complex vortices formation in the group with aneurysm growth, leading to an average pressure increase in the ascending aortic wall between exams. In the group without aneurysm growth, the average pressure decreased. Conclusion This pilot study showed that CFD based on CTA may in the near future be a tool to help identify flow patterns associated with AsAA remodeling process.

Incidence of Conduction Disorders and Requirements for Permanent Pacemaker After Transcatheter Aortic Valve Implantation

Transcatheter aortic valve implantation (TAVI) has become a therapeutic option for high-risk or non-operable patients with severe symptomatic aortic stenosis. Atrioventricular conduction disturbances requiring permanent pacemaker (PPM) are a common and clinically important complication. Objectives: To evaluate the incidence of conduction disorders (CDs) after TAVI and the need for subsequent PPM implantation. To identify the predictors of postoperative PPM implantation. Methods: Retrospective study. All patients who underwent TAVI in a public hospital from December/2011 to June/2016 were included. Multivariate analysis was conducted to establish the predictor of permanent pacemaker implantation. Survival curves were constructed by the Kaplan-Meyer method. Statistically significant variables were those with p value < 0.05. Results: 64 patients with AS underwent TAVI. Eleven patients were excluded. TAVI induced a new CD in 40 (77%) of the remaining 53 patients. The most common new CDs were 3rd degree AV block (32%) and left bundle branch block (30%). Sixteen patients (30,2%) underwent PPM implantation during the index hospitalization. On univariate analysis the risk factors for PPM implantation were CoreValve® use (OR: 1,76; P = 0,005), larger prosthesis implantation (P = 0,015), presence of a QRS ≥ 120 ms (OR: 5,62; P = 0,012), and 1st degree AV block (OR: 13; P = 0.008). On multivariate analysis the presence of 1st degree AV block predicted the need for PPM. Conclusion: TAVI induced CDs requiring PPM in 30% of the patients. The presence of 1st degree AV block predicted the need for PPM

Echocardiographic assessment of right ventricular function by two-dimensional strain in patients with left-sided valvular heart disease: comparison whit three-dimendional echocardiography / Avaliação ecocardiográfica da função ventricular direita por strain bidimensional em pacientes com valvopatia à esquerda: comparação com ecocardiografia tridimensional

Background: Right ventricular (RV) dysfunction is a well-known predictor of mortality in patients with valvular heart disease (VHD). The assessment of RV function is often difficult due to complex geometry and hemodynamic factors. Objective: We aim to analyze RV function in patients with severe mitral and/or aortic valve disease using two-dimensional strain (2DS) imaging and conventional echocardiographic parameters, comparing it with right ventricular ejection fraction (RVEF) measured by three-dimensional echocardiography (3DE). Methods: Fifty-three patients with severe mitral and/or aortic VHD underwent complete transthoracic echocardiogram in the preoperative setting for cardiac surgery, including conventional echocardiographic parameters of RV function and speckle-tracking derived 2DS indices: RV global longitudinal strain (RVGS) and RV free wall longitudinal strain (RVFWS). Conventional echocardiographic and 2DS parameters were compared with real-time 3DE RVEF using Spearman correlation test. For comparison between two groups of patients based on the presence of RV dysfunction (normal RVEF ≥ 44% - A, abnormal RVEF < 44% - B), we used nonparametric Mann-Whitney U test. ROC (receiver operating characteristic) curve analysis was used to assess the clinical utility of all RV function variables in defining RV dysfunction. P values <0,05 were considered statistically significant.Results: We found a significant correlation between all parameters and RVEF (p<0.05), with best results for RV fractional area change (FAC), RVGS, and RVFWS. Dividing the population into two-groups based on RVEF, we found 14 patients with RV dysfunction (27.4%), and significant differences between the groups for all RV function variables. For detection of RV dysfunction defined by 3DE, ROC curve analysis showed the best area under the curve (AUC) for RVGS (0.872), RVFWS (0.851) and FAC (0.932). Conclusions: We observed significant correlation between RVGS, RVFWS and RVEF, with good accuracy in detecting RV dysfunction, comparable to FAC and better than other conventional parameters of RV function assessment. The evaluation of RV myocardial deformation with 2DS may have additional diagnostic and prognostic value in patients with severe left-sided VHD

Transcatheter aortic valve replacement: the experience of one brazilian health care center

Abstract Objective: Transcatheter aortic valve replacement has been an alternative to invasive treatment for symptomatic severe aortic stenosis in high risk patients. The primary endpoint was 30-day and 1-year mortality from any cause. Secondary endpoints were to compare the clinical and echocardiographic variation pre-and post- transcatheter aortic valve replacement, and the occurrence of complications throughout a 4-year follow-up period. Methods: This prospective cohort, nestled to a multicenter study (Registro Brasileiro de Implante de Bioprótese por Cateter), describes the experience of a public tertiary center in transcatheter aortic valve replacement. All patients who underwent this procedure between October 2011 and February 2016 were included. Results: Fifty-eight patients underwent transcatheter aortic valve replacement. The 30-day all-cause mortality was 5.2% (n=3) and after 1 year was 17.2% (n=10). A significant improvement in New York Heart Association functional classification was observed when comparing pre-and post- transcatheter aortic valve replacement (III or IV 84.4% versus 5.8%; P<0.001). A decline in peak was observed (P<0.001) and mean (P<0.001) systolic transaortic gradient. The results of peak and mean post-implant transaortic gradient were sustained after one year (P=0.29 and P=0.36, respectively). Left ventricular ejection fraction did not change significantly during follow-up (P=0.41). The most frequent complications were bleeding (28.9%), the need for permanent pacemaker (27.6%) and acute renal injury (20.6%). Conclusion: Mortality and complications in this study were consistent with worldwide experience. Transcatheter aortic valve replacement had positive clinical and hemodynamic results, when comparing pre-and post-procedure, and the hemodynamic profile of the prosthesis was sustained throughout follow-up.