Tricuspid annular area and leaflets stretch are associated with functional tricuspid regurgitation - insights from three-dimensional transesophageal echocardiography

BACKGROUND

The presence of functional tricuspid regurgitation (TR) is associated with mortality and morbidity. Although uniform management with a tricuspid annuloplasty ring is currently considered as a standard surgical procedure, high rates of residual TR despite annuloplasty are reported. Therefore, the identification of the TR mechanisms would be necessary to provide personalized treatment for each TR patient.

METHODS

This study population consisted of 106 patients with mitral regurgitation (MR) who were scheduled for procedure. Transthoracic and transesophageal echocardiography were performed prior to mitral valve intervention. We performed three-dimensional quantitative assessment including tricuspid annular (TA) area and the distance between the three commissures of tricuspid valve.

RESULTS

Significant TR, which is defined as moderate or greater TR, was detected in 23 (22%). TA area (P < 0.01), the distance of septal-leaflet length (SL) (P = 0.03) and posterior-leaflet length (PL) (p = 0.02) were significantly associated with significant TR, while TA diameter assessed by transthoracic echocardiography was not. When patients were divided into four groups according to SL and PL, the group with longer SL and PL had a significantly higher incidence of significant TR (P < 0.01).

CONCLUSIONS

Greater stretch of the septal and posterior leaflet between commissures and larger TA area are associated with significant TR in patients with severe MR. In order to prevent TR recurrence, the intervention of the septal leaflet in tricuspid annuloplasty may be beneficial. The precise implement of three-dimensional transesophageal echocardiography of tricuspid valve is valuable for a personalized strategy of tricuspid annuloplasty.

Left atrial volume index predicts future improvement of B-type natriuretic peptide levels after transcatheter aortic valve replacement

In patients with symptomatic severe aortic stenosis (AS), those who experienced readmission due to heart failure after transcatheter aortic valve replacement (TAVR) showed poor prognosis. Furthermore, poor B-type natriuretic peptide (BNP) improvement is associated with increased morbidity and mortality. However, little is known about the clinical parameters related to the change in BNP levels after TAVR procedure. This study population consisted of 127 consecutive patients of symptomatic severe AS with preserved ejection fraction (EF) who underwent transfemoral TAVR (TF-TAVR). Comprehensive transthoracic echocardiography was performed prior to the day of TF-TAVR. BNP was measured serially before and 1 year after TF-TAVR. The median BNP level was significantly decreased from 252.5 pg/ml to 146.8 pg/ml in all 127 patients 1 year after TF-TAVR (P < 0.01). However, the patients could be divided into 2 groups according to decrease (72%) or increase (28%) in plasma BNP level. Multivariate logistic regression analysis revealed that Aortic valve (AV) peak velocity, pre-procedural BNP, and larger left atrial volume index (LAVI) were found to be an independent predictor of increased BNP level 1 year after TAVR (OR 0.55, 95% CI 0.38-0.77; P < 0.01). LAVI were negatively correlated with the change in BNP level before and 1 year after TAVR (r = 0.47, P < 0.01). The ROC analysis demonstrated that 52.9 ml/m2 was the optimal cut-off value of LAVI for decreasing BNP 1 year after TAVR (area under the curve 0.69) with 64% sensitivity and 70% specificity. In addition to AV peak velocity and pre-procedural BNP, LAVI independently predicts future improvement of BNP levels 1 year after TAVR. Our findings indicate an additive predictive value of assessment of LAVI before TAVR procedure for risk stratification.

Prevalence and Risk Factors of Silent Brain Infarction in Patients with Aortic Stenosis

Introduction

Silent brain infarction (SBI) is an independent risk factor for subsequent symptomatic stroke in the general population. Although aortic stenosis (AS) is also known to be associated with an increased risk of future symptomatic stroke, little is known regarding the prevalence and risk factors for SBI in patients with AS.

Methods

The study population comprised 83 patients with severe AS with no history of stroke or transient ischemic attack and paralysis or sensory impairment (mean age 75 ± 7 years). All patients underwent brain magnetic resonance imaging to screen for SBI and multidetector-row computed tomography to quantify the aortic valve calcification (AVC) volume. Comprehensive transthoracic and transesophageal echocardiography were performed to evaluate left atrial (LA) abnormalities, such as LA enlargement, spontaneous echo contrast, or abnormal LA appendage emptying velocity (<20 cm/s), and complex plaques in the aortic arch.

Results

SBI was detected in 38 patients (46%). Multiple logistic regression analysis indicated that CHA₂DS₂-VASc score and estimated glomerular filtration rate (eGFR) were independently associated with SBI (p < 0.05), whereas LA abnormalities and AVC volume were not. When patients were divided into 4 groups according to CHA₂DS₂-VASc score and eGFR, the group with a higher CHA₂DS₂-VASc score (≥4) and a lower eGFR (<60 mL/min/1.73 m²) had a greater risk of SBI than the other groups (p < 0.05).

Conclusion

These findings indicate that AS is associated with a high prevalence of SBI, and that the CHA₂DS₂-VASc score and eGFR are useful for risk stratification.

3-D diffusion tensor MRI anisotropy content-adaptive finite element head model generation for bioelectromagnetic imaging

Realistic finite element (FE) head models have been successfully applied to bioelectromagnetic problems due to a realistic representation of arbitrary head geometry with inclusion of anisotropic material properties. In this paper, we propose a new automatic FE mesh generation scheme to generate a diffusion tensor MRI (DT-MRI) white matter anisotropy content-adaptive FE head model. We term this kind of mesh as wMesh. With this meshing technique, the anisotropic electrical conductivities derived from DT-MRIs can be best incorporated into the model. The influence of the white matter anisotropy on the EEG forward solutions has been studied via our wMesh head models. The scalp potentials computed from the anisotropic wMesh models against those of the isotropic models have been compared. The results describe that there are substantial changes in the scalp electrical potentials between the isotropic and anisotropic models, indicating that the inclusion of the white matter anisotropy is critical for accurate computation of E/MEG forward and inverse solutions. This fully automatic anisotropy-adaptive wMesh meshing scheme could be useful for modeling of individual-specific FE head models with better incorporation of the white matter anisotropic property towards bioelectromagnetic imaging.

Characterization of antioxidant properties of natural killer-enhancing factor-B and induction of its expression by hydrogen peroxide

Natural killer-enhancing factor B (NKEF-B) belongs to a highly conserved family of recently discovered antioxidants. The role of NKEF-B as an antioxidant was demonstrated by its protection of transfected cells to oxidative damage by hydrogen peroxide. To further characterize the antioxidant properties of NKEF-B, we compared the sensitivity of a human endothelial cell line ECV304 and its transfectant, B/1 that hyperexpresses NKEF-B, to various oxidants. In addition, we investigated the changes in the expression of NKEF-B mRNA upon oxidative stress. We found that B/1 was significantly more resistant than the control cells to the oxidative stresses caused by t-butyl hydroperoxide (t-BHP) and methyl mercury (MeHg). In contrast, there was no difference in the sensitivity of B/1 and the control cells to sulfhydryl reactive agents, diethyl maleate and diamide. B/1 was also as sensitive as the control cells to buthionine sulfoximine. The expression of NKEF-B mRNA was induced when the parental cell line ECV304 was treated with 2 mm HP. The induction reached a maximum level around 2 hr and decreased to the basal level around 4 hr. NKEF-A mRNA was not induced by HP. These results demonstrate antioxidant activities of NKEF-B toward prooxidants such as alkyl hydroperoxide and MeHg. Together with its antioxidant activity, the induction of NKEF-B by HP indicates that NKEF-B is an important oxidative stress protein providing protection against a variety of xenobiotic toxic agents.

Endogenous natural killer enhancing factor-B increases cellular resistance to oxidative stresses

Natural killer-enhancing factor (NKEF) was identified and cloned on the basis of its ability to increase NK cytotoxicity. Two genes, NKEF-A and -B, encode NKEF proteins and sequence analysis presented suggests that each belongs to a highly conserved family of antioxidants. To examine the antioxidant potential of NKEF, we transfected the coding region of NKEF-B cDNA into the human endothelial cell line ECV304. The stable transfectant, B/1, was found to overexpress NKEF-B gene transcript and protein. We subjected B/1 to oxidative stress by either culturing them with glucose oxidase (GO), which continuously generates hydrogen peroxide, or by direct addition of hydrogen peroxide. We found that B/1 cells were more resistant than control cell lines. Resistance to hydrogen peroxide was originally thought to be mediated mainly by catalase and the glutathione cycle. Therefore, we used inhibitors to block the two pathways and found that B/1 cells were more resistant to oxidative stress than control cells when we used inhibitors to preblock either pathway. We also examined the cellular inflammatory responses to oxidized low-density lipoprotein (LDL) and bacterial lipopolysaccharide (LPS) by measuring monocyte adhesion to endothelial cells in vitro and found that B/1 cells were resistant to such responses. Lastly, we found that B/1 cells were more resistant to a novel chemotherapeutic agent CT-2584, which appears to kill tumor cells by stimulating production of reactive oxygen intermediates in mitochondria. These results demonstrate that the NKEF-B is an antioxidant that protects cells from oxidative stress, chemotherapy agents, and inflammation-induced monocyte adhesion. Furthermore, its expression may mediate cellular responses to proinflammatory molecules.

Recombinant natural killer enhancing factor augments natural killer cytotoxicity

Natural killer enhancing factor (NKEF) was originally identified and studied because of its ability to enhance NK cytotoxicity in vitro. After cloning the two genes responsible for NKEF proteins, NKEF-A and -B, we found that they belong to a newly described and highly conserved antioxidant gene family. We have now produced recombinant proteins of both genes and used them to test for their ability to promote NK cytotoxicity. Although recombinant NKEF (rNKEF)-A and -B have similar levels of antioxidant function, only the reduced form of rNKEF-A can enhance NK cytotoxicity. These results indicate that both the antioxidant and NK-enhancing functions of rNKEF-A and -B probably involve the cysteine residues of the proteins but are mediated by separate domains of the molecules. We pretreated both effector cells and target cells to investigate which population was influenced by rNKEF-A, and determined that the protein must be present during the cytotoxicity assay to enhance the activity. Despite the similarities between NK cytotoxicity and lymphokine-activated killer (LAK) cytotoxicity, rNKEF-A is not effective in augmenting LAK cytotoxicity. Therefore, rNKEFs can be useful tools in not only protecting cells from oxidative damage, but also in selectively promoting NK cytotoxicity against certain tumor cells.

Characterization of an oxidation-resistant tumor cell line and its sensitivity to immune response and chemotherapy

Aerobic cells have several scavenger systems for protection from reactive oxygen species (ROS). We developed an ROS-resistant variant of the human erythroleukemic cell line K562 by culturing cells in glucose oxidase to produce hydrogen peroxide. Testing the activity of the scavenger systems for ROS showed these cells had a 25- to 28-fold increase in catalase activity. We therefore termed this variant cell line K562-CAT. There was no similar increase in glutathione content or activity of superoxide dismutase and glutathione peroxidase. To determine what effect the increased catalase activity would have on the immune response to these tumor cells, we compared K562 and K562-CAT sensitivity to tumor necrosis factor-alpha (TNF alpha) activated polymorphonuclear neutrophil (PMN), natural killer (NK), and lymphokine-activated killer (LAK) cells. K562-CAT showed a significant increase in resistance to TNF alpha-activated PMN but not to NK or LAK, confirming the role of ROS in the former but not the latter. We also tested K562-CAT sensitivity to cisplatin and mitomycin C, agents known to involve ROS in their cytotoxic mechanism. There was no increased resistance in K562-CAT compared to parental K562, indicating that catalase is not involved in tumor cell resistance to those drugs. Given the characteristics of its resistance to the immune response, K562-CAT or a similar catalase-hyperexpressing cell line could be useful in determining the significance of TNF alpha-activated PMN in antitumor defenses.