Supra-annular Valve-in-Valve implantation reduces blood stasis on the transcatheter aortic valve leaflets

Leaflet thrombosis following transcatheter aortic valve replacement (TAVR) and Valve-in-Valve (ViV) procedures has been increasingly recognized. This study aimed to investigate the effect of positioning of the transcatheter aortic valve (TAV) in ViV setting on the flow dynamics aspect of post-ViV thrombosis by quantifying the blood stasis in the intra-annular and supra-annular settings. To that end, two idealized computational models, representing ViV intra-annular and supra-annular positioning of a TAV were developed in a patient-specific geometry. Three-dimensional flow fields were then obtained via fluid-solid interaction modeling to study the difference in blood residence time (BRT) on the TAV leaflets in the two settings. At the end of diastole, a strip of high BRT ($⩾1.2s$) region was observed on the TAV leaflets in the ViV intra-annular positioning at the fixed boundary where the leaflets are attached to the frame. Such a high BRT region was absent on the TAV leaflets in the supra-annular positioning. The maximum value of BRT on the surface of non-, right, and left coronary leaflets of the TAV in the supra-annular positioning were 53%, 11%, and 27% smaller compared to the intra-annular positioning, respectively. It was concluded that the geometric confinement of TAV by the leaflets of the failed bioprosthetic valve in ViV intra-annular positioning increases the BRT on the leaflets and may act as a permissive factor in valvular thrombosis. The absence of such a geometric confinement in the ViV supra-annular positioning leads to smaller BRT and subsequently less likelihood of leaflet thrombosis.     

Sphingosine-1-phosphate inhibits cell migration and endothelial to mesenchymal cell transformation during cardiac development

Sphingosine-1-phosphate (S1P) is a biologically active sphingolipid metabolite that exerts important effects on numerous cellular events via cell surface receptors, S1P(1-5). S1P influences differentiation, proliferation, and migration during vascular development. However, the effects of S1P signaling on early cardiac development are not well understood. To address this issue, we examined the expression of S1P regulatory enzymes and S1P receptors during cardiac development. We observed that enzymes that regulate S1P levels, sphingosine kinase and sphingosine-1-phosphate phosphatase, are expressed in the developing heart. In addition, RT-PCR revealed that four of the five known S1P receptors (S1P(1-4)) are also expressed in the developing heart. Next, effects of altered S1P levels on whole embryo and atrioventricular (AV) canal cultures were investigated. We demonstrate that inactivation of the S1P producing enzyme, sphingosine kinase, leads to cell death in cardiac tissue which is rescued by exogenous S1P treatment. Other experiments reveal that increased S1P concentration prevents alterations in cell morphology that are required for cell migration. This effect results in reduced cell migration and inhibited mesenchymal cell formation in AV canal cushion tissue. These data indicate that S1P, locally maintained within a specific concentration range, is an important and necessary component of early heart development.     

Simultaneous Accessory Pathway and AV Node Mechanical Block

We report a clinical case of a 22-year-old female referred to our institution due to palpitations and preexcitation. Her ECG suggested a right superior paraseptal accessory pathway (AP), which was localised during the electrophysiological study at the superior paraseptal region in close proximity to the His recordings. Reproducible orthodromic reciprocating tachycardia was induced by atrial pacing with extrastimuli. Cryo-mapping performed in the area of earliest atrial activation was not able to terminate the tachycardia. A second attempt, slightly more posterior, caused mechanical block of the AP, which rendered the tachycardia non-inducible. More pressure with the ablation catheter determined a Wenckebach type supra-hisian AV block, which was transient but reproducible. Given this finding no ablation was done. Simultaneous block to the AP and the atrioventricular node has rarely been reported using radiofrequency energy. However, to our knowledge this phenomenon has not been previously reported in large series using cryo-thermal energy.     

乌司他丁联合丙氨酰谷氨酰胺对体外循环瓣膜置换术患者炎症反应及肺功能的影响

目的:探讨体外循环(CPB)瓣膜置换术应用乌司他丁(ULi)联合丙氨酰谷氨酰胺(Ala-Gln)联合干预对患者机体炎症反应及肺功能的影响。方法:选取我院2013年6月~2016年11月收治并择期行CPB瓣膜置换术的54例患者,随机分为两组。对照组采用常规方法治疗,观察组采用丙氨酰谷氨酰胺(Ala-Gln)联合乌司他丁(ULi)。观察并比较两组患者围术期血清炎性因子及肺表面活性蛋白A(SP-A)水平、肺功能指标及机械通气时间。结果:与本组T_0时相比,两组在T_2、T_3、T_4、T_5血清IL-6、IL-8、T_NF-α及SP-A水平均显著升高(P0.01);与对照组同期对比,观察组在T_2、T_3、T_4、T_5的血清炎性因子及SP-A水平更低(P0.01)。与本组T_0时比较,两组在T_2、T_3、T_4、T_5的RI、A-a DO2值均显著上升(P0.01);观察组在T_2、T_3、T_4、T_5各时点的RI、A-a DO2值均显著低于对照组同期(P0.01)。与本组T_0时对比,两组在T_1时的Cst值均显著提高(P0.01)。观察组机械通气时间显著低于对照组(P0.01)。结论:CPB瓣膜置换术患者应用ULi联合Ala-Gln干预更能有效控制机体炎症反应,保护肺功能,值得临床推广应用。     

Diversity of mineral cell coverings and their formation processes: a review focused on the siliceous cell coverings

Mineral cell coverings are found in various protists. Some macroalgae accumulate calcium carbonate in the intercellular space, and some unicellular organisms use calcium carbonate or silica for the construction of loricas, scales, and frustules. Diatoms are representatives of those utilizing silica for the material of the cell covering called a frustule. The development of the frustule is initiated in a silica-deposition vesicle (SDV), which occurs just beneath the plasma membrane and, subsequently, the silicified cell covering expands its area, following the expansion of the SDV from valve face to valve mantle. Sequential valve development with whole valves is reviewed in several diatoms placed in different phylogenetic positions. Every diatom commences its valve formation from its pattern center and then develops by means of individual procedures. The results indicate that the valve development reflects the phylogeny of diatoms. In addition, recent progress in silica biomineralization is briefly reviewed, and the phylogeny of ability concerning siliceous cell covering formation is inferred. Electronic Publication     

Long-term outcomes of isolated aortic valve replacement and concomitant AVR and coronary artery bypass grafting

Background

It is well established that concomitant aortic valve replacement (AVR) and coronary artery bypass grafting (CABG) has a higher operative mortality rate than isolated AVR. However, studies report conflicting results on the long-term mortality. The aim of this prospective study was to explore and compare the outcomes and risk factors of isolated AVR and concomitant AVR and CABG in a consecutive Dutch patient population.

Methods

From January 2001 through January 2010, 332 consecutive patients underwent AVR with or without CABG at a single institution (197 isolated AVR and 135 concomitant AVR and CABG). A multivariate Cox proportional hazard analysis was performed to determine the independent risk factors for long-term mortality after aortic valve replacement.

Results

All 332 consecutive, referred patients who underwent aortic valve surgery were followed for up to 10 years. Median follow-up length was 48 months. The population had a median age of 73 years (IQR 65–78) and predominantly consisted of males (62%). Patients in the combined AVR and CABG group were older, had worse cardiac risk profiles and had worse preoperative cardiac statuses than those receiving isolated AVR. Five-year survival was 85% in AVR and 73% in AVR-CABG (p-value 0.012). Independent risk factors for mortality were higher creatinine values, previous CABG and increasing age.

Conclusion

Unselected, consecutive patients who underwent aortic valve replacement surgery and who received concomitant bypass surgery between 2001–2010 had higher 5-year mortality than their counterparts without CABG. Prior CABG, renal function, age but not concomitant CABG remained independently associated with increased mortality. Finally, the observed mortality rate in this consecutive patient group compared favourably with preoperative risk assessment using the EuroSCORE.