Early Feasibility Study of a Hybrid Tissue-Engineered Mitral Valve in an Ovine Model.

Tissue engineering aims to overcome the current limitations of heart valves by providing a viable alternative using living tissue. Nevertheless, the valves constructed from either decellularized xenogeneic or purely biologic scaffolds are unable to withstand the hemodynamic loads, particularly in the left ventricle. To address this, we have been developing a hybrid tissue-engineered heart valve (H-TEHV) concept consisting of a nondegradable elastomeric scaffold enclosed in a valve-like living tissue constructed from autologous cells. We developed a 21 mm mitral valve scaffold for implantation in an ovine model. Smooth muscle cells/fibroblasts and endothelial cells were extracted, isolated, and expanded from the animal's jugular vein. Next, the scaffold underwent a sequential coating with the sorted cells mixed with collagen type I. The resulting H-TEHV was then implanted into the mitral position of the same sheep through open-heart surgery. Echocardiography scans following the procedure revealed an acceptable valve performance, with no signs of regurgitation. The valve orifice area, measured by planimetry, was 2.9 cm2, the ejection fraction reached 67%, and the mean transmitral pressure gradient was measured at 8.39 mmHg. The animal successfully recovered from anesthesia and was transferred to the vivarium. Upon autopsy, the examination confirmed the integrity of the H-TEHV, with no evidence of tissue dehiscence. The preliminary results from the animal implantation suggest the feasibility of the H-TEHV.

Generalizable fully automated multi-label segmentation of four-chamber view echocardiograms based on deep convolutional adversarial networks.

A major issue in translation of the artificial intelligence platforms for automatic segmentation of echocardiograms to clinics is their generalizability. The present study introduces and verifies a novel generalizable and efficient fully automatic multi-label segmentation method for four-chamber view echocardiograms based on deep fully convolutional networks (FCNs) and adversarial training. For the first time, we used generative adversarial networks for pixel classification training, a novel method in machine learning not currently used for cardiac imaging, to overcome the generalization problem. The method's performance was validated against manual segmentations as the ground-truth. Furthermore, to verify our method's generalizability in comparison with other existing techniques, we compared our method's performance with a state-of-the-art method on our dataset in addition to an independent dataset of 450 patients from the CAMUS (cardiac acquisitions for multi-structure ultrasound segmentation) challenge. On our test dataset, automatic segmentation of all four chambers achieved a dice metric of 92.1%, 86.3%, 89.6% and 91.4% for LV, RV, LA and RA, respectively. LV volumes' correlation between automatic and manual segmentation were 0.94 and 0.93 for end-diastolic volume and end-systolic volume, respectively. Excellent agreement with chambers' reference contours and significant improvement over previous FCN-based methods suggest that generative adversarial networks for pixel classification training can effectively design generalizable fully automatic FCN-based networks for four-chamber segmentation of echocardiograms even with limited number of training data.

Serial changes of L wave according to heart rates in a heart failure patient with persistent atrial fibrillation.

Mid-diastolic forward flow velocity of transmitral flow (L wave) is known as a marker of diastolic dysfunction and is occasionally observed in patients with fluid retention, low heart rate, and atrial fibrillation (AF). However, how hemodynamic condition affects L wave is still unknown. An 81-year-old woman who underwent implantation of a DDD pacemaker due to complete atrioventricular block 38 years previously suffered from congestive heart failure and was admitted to our hospital. At the time of admission, electrocardiogram showed new-onset AF resulting in mode switch to VVI, and echocardiography showed a giant L wave. At the mid-term of the treatment, AF was converted to sinus rhythm resulting in mode switch to DDD, and pacemaker check-up was performed at pre- and post-cardioversion. During the pacemaker check-ups, L wave was assessed in various pacing rates. As pacing rate was increased, L wave altered according to heart rates and disappeared at 85 bpm in VVI with AF, whereas at 75 bpm in DDD. Through the treatment, L wave got smaller as fluid retention was improved and finally disappeared at the time of discharge. This case suggests that L wave is highly variable and affected by fluid volume, heart rate, and heart rhythm. .

Reduction in Left Ventricular Ejection Fraction is Associated with Subsequent Cardiac Events in Outpatients with Chronic Heart Failure.

Left ventricular ejection fraction (LVEF) is critical for determining the prognosis and treatment of patients with heart failure (HF). However, the influence of serial LVEF changes in patients with stable chronic HF (CHF) has not yet been completely investigated. We analyzed data of 263 outpatients with CHF from the J-MELODIC study cohort and evaluated the frequency of cardiac events. We stratified patients into tertiles based on the relative difference in LVEF in 1 year and that at baseline. We found a significant difference in the cardiac event rate among the three groups (log-rank test, p = 0.042). We identified a relative 11% LVEF reduction as the optimal cutoff value based on the receiver operating characteristics analysis. LVEF (OR, 1.04; 95% CI, 1.01-1.07; p = 0.015) and E/e' (OR, 1.06; 95% CI, 1.01-1.12; p = 0.023) at baseline were predictors of >11% LVEF reduction. After adjusting the variables including age and sex, >11% LVEF reduction was an independent predictor of subsequent cardiac events (HR, 5.79; 95% CI, 2.49-13.2; p < 0.001). In conclusion, patients with 1-year relative >11% LVEF reduction may have subsequent worsening outcomes. Such patients should be carefully followed-up as high risk population for development of cardiac events.

Age-related changes in diastolic function in children: Echocardiographic association with vortex formation time.

BACKGROUND: This study aims to understand the age-related changes in vortex formation time (VFT) index in children, and thus, describe the ranges of VFT in different pediatric age groups with the ultimate goal of assessment of diastolic function. METHODS AND RESULTS: Transthoracic echocardiograms in healthy (n = 84) subjects from birth to 20 years were analyzed to compute VFT and diastolic performance. LV apical and short-axis views were used. Three separate measurements were performed, and the mean was used to derive VFT and other indices. Statistical comparisons were made amongst the groups, stratified by age. RESULTS: Vortex formation times in neonates (median 1.79, interquartile range 1.31-1.92) and infants (1.38, 1.07-1.72) were found to be significantly lower (P < .05) than the older age groups (1-5 years 2.47, 1.87-2.94, 5-10 years 2.18, 1.89-2.53, 10-20 years 2.34, 1.84-2.96). The changes in VFT correlate to the changes in diastolic function in children. CONCLUSION: Our results show that unlike adults, VFT changes along with the growth-related myocardial adaptations in children, and its range may be used to evaluate diastolic function. The present study is the first to test the significance of the trans-mitral VFT in children by comparing different age groups of healthy subjects.

Diagnostic and prognostic significance of cardiovascular vortex formation.

Various forms of vortex formation in the cardiovascular system convey valuable information regarding the function of heart and great vessels. The vortex ring that forms during systole in the aortic sinus is the first that was recognized and the asymmetric transmitral vortex ring that forms in the left ventricle during diastole has been most commonly used for diagnosis and follow up of heart failure patients. Adverse vortex interaction in the heart can also occur due to valvular regurgitation and may have energetic consequences to the heart. Furthermore, vortices do exist in other chambers such as the right ventricle and may even arise in the great arteries and veins due to congenital heart disease. Here, we summarize diagnostic and prognostic significance of vortices and vortex imaging in the heart, their applications in clinical medicine, and discuss how these flow features can be used to assess functional status of the heart.

Intraventricular Vortex Interaction between Transmitral Flow and Paravalvular Leak.

Paravalvular leak (PVL) is a complication of transcatheter aortic valve replacement. Despite its marked clinical impact, no previous study has reported how PVL affects the intraventricular fluid dynamics. This study aims to delineate vortex interaction between PVL and transmitral flow and the influence of PVL orifice location on intraventricular fluid dynamics using Echocardiographic Particle Image Velocimetry. Three different conditions of no PVL, anterior PVL and posterior PVL were experimentally studied and clinically compared. Circulation, impulse, kinetic energy (KE) and change in KE (ΔKE) were calculated. As well, vortex formation analyses and streamline description were performed to study vortex interactions. The anterior PVL jet streamed into the LV and interfered with the transmitral flow. Posterior PVL jet formed a large clockwise vortex and collided with transmitral flow, which resulted in flow disturbance. Compared to no PVL condition, average circulation, impulse, KE and ΔKE increased in presence of PVL. In conclusion, we found that PVL jets lead to abnormal vortex formation that interfere with natural advancement of transmitral flow, and negatively affect the LV fluid dynamics parameters. PVL orifice location strongly affects the intraventricular vortex formation, and posterior PVL may have more negative effects compared to anterior PVL.

A calcified polymeric valve for valve-in-valve applications.

The prevalence of aortic valve stenosis (AS) is increasing in the aging society. More recently, novel treatments and devices for AS, especially transcatheter aortic valve replacement (TAVR) have significantly changed the therapeutic approach to this disease. Research and development related to TAVR require testing these devices in the calcified heart valves that closely mimic a native calcific valve. However, no animal model of AS has yet been available. Alternatively, animals with normal aortic valve that are currently used for TAVR experiments do not closely replicate the aortic valve pathology required for proper testing of these devices. To solve this limitation, for the first time, we developed a novel polymeric valve whose leaflets possess calcium hydroxyapatite inclusions immersed in them. This study reports the characteristics and feasibility of these valves. Two types of the polymeric valve, i.e., moderate and severe calcified AS models were developed and tested by deploying a transcatheter valve in those and measuring the related hemodynamics. The valves were tested in a heart flow simulator, and were studied using echocardiography. Our results showed high echogenicity of the polymeric valve, that was correlated to the severity of the calcification. Aortic valve area of the polymeric valves was measured, and the severity of stenosis was defined according to the clinical guidelines. Accordingly, we showed that these novel polymeric valves closely mimic AS, and can be a desired cost-saving solution for testing the performance of the transcatheter aortic valve systems in vitro.

Association of dietary iron restriction with left ventricular remodeling after myocardial infarction in mice.

Several epidemiologic studies have reported that body iron status and dietary iron intake are related to an increased risk of acute myocardial infarction (MI). However, it is completely unknown whether dietary iron reduction impacts the development of left ventricular (LV) remodeling after MI. Here, we investigate the effect of dietary iron restriction on the development of LV remodeling after MI in an experimental model. MI was induced in C57BL/6 J mice (9-11 weeks of age) by the permanent ligation of the left anterior descending coronary artery (LAD). At 2 weeks after LAD ligation, mice were randomly divided into two groups and were given a normal diet or an iron-restricted diet for 4 weeks. Sham operation without LAD ligation was also performed as controls. MI mice exhibited increased LV dilatation and impaired LV systolic function that was associated with cardiomyocyte hypertrophy and interstitial fibrosis in the remote area, as compared with the controls at 6 weeks after MI. In contrast, dietary iron restriction attenuated LV dilatation and impaired LV systolic function coupled to cardiomyocyte hypertrophy and interstitial fibrosis in the remote area. Importantly, cardiac expression of cellular iron transport proteins, transferrin receptor 1 and divalent metal transporter 1 was increased in the remote area of MI mice compared with the controls. Dietary iron restriction attenuated the development of LV remodeling after MI in mice. Cellular iron transport might play a role in the pathophysiological mechanism of LV remodeling after MI.

Transferrin Receptor 1 in Chronic Hypoxia-Induced Pulmonary Vascular Remodeling.

BACKGROUND: Iron is associated with the pathophysiology of several cardiovascular diseases, including pulmonary hypertension (PH). In addition, disrupted pulmonary iron homeostasis has been reported in several chronic lung diseases. Transferrin receptor 1 (TfR1) plays a key role in cellular iron transport. However, the role of TfR1 in the pathophysiology of PH has not been well characterized. In this study, we investigate the role of TfR1 in the development of hypoxia-induced pulmonary vascular remodeling. METHODS: PH was induced by exposing wild-type (WT) mice and TfR1 hetero knockout mice to hypoxia for 4 weeks and evaluated via assessment of pulmonary vascular remodeling, right ventricular (RV) systolic pressure, and RV hypertrophy. In addition, we assessed the functional role of TfR1 in pulmonary artery smooth muscle cells in vitro. RESULTS: The morphology of pulmonary arteries did not differ between WT mice and TfR1 hetero knockout mice under normoxic conditions. In contrast, TfR1 hetero knockout mice exposed to 4 weeks hypoxia showed attenuated pulmonary vascular remodeling, RV systolic pressure, and RV hypertrophy compared with WT mice. In addition, the depletion of TfR1 by RNA interference attenuated human pulmonary artery smooth muscle cells proliferation induced by platelet-derived growth factor-BB (PDGF-BB) in vitro. CONCLUSIONS: These results suggest that TfR1 plays an important role in the development of hypoxia-induced pulmonary vascular remodeling.

Temporary dietary iron restriction affects the process of thrombus resolution in a rat model of deep vein thrombosis.

BACKGROUND: Deep vein thrombosis (DVT) is a major cause of pulmonary thromboembolism and sudden death. Thus, it is important to consider the pathophysiology of DVT. Recently, iron has been reported to be associated with thrombotic diseases. Hence, in this study, we investigate the effects of dietary iron restriction on the process of thrombus resolution in a rat model of DVT. METHODS: We induced DVT in 8-week-old male Sprague-Dawley rats by performing ligations of their inferior venae cavae. The rats were then given either a normal diet (DVT group) or an iron-restricted diet (DVT+IR group). Thrombosed inferior venae cavae were harvested at 5 days after ligation. RESULTS: The iron-restricted diet reduced venous thrombus size compared to the normal diet. Intrathrombotic collagen content was diminished in the DVT+IR group compared to the DVT group. In addition, intrathrombotic gene expression and the activity of matrix metalloproteinase-9 were increased in the DVT+IR group compared to the DVT group. Furthermore, the DVT+IR group had greater intrathrombotic neovascularization as well as higher gene expression levels of urokinase-type plasminogen activator and tissue-type plasminogen activator than the DVT group. The iron-restricted diet decreased intrathrombotic superoxide production compared to the normal diet. CONCLUSIONS: These results suggest that dietary iron restriction affects the process of thrombus resolution in DVT.

Iron restriction inhibits renal injury in aldosterone/salt-induced hypertensive mice.

Excess iron is associated with the pathogenesis of several renal diseases. Aldosterone is reported to have deleterious effects on the kidney, but there have been no reports of the role of iron in aldosterone/salt-induced renal injury. Therefore, we investigated the effects of dietary iron restriction on the development of hypertension and renal injury in aldosterone/salt-induced hypertensive mice. Ten-week-old male C57BL/6J mice were uninephrectomized and infused with aldosterone for four weeks. These were divided into two groups: one fed a high-salt diet (Aldo) and the other fed a high-salt with iron-restricted diet (Aldo-IR). Vehicle-infused mice without a uninephrectomy were also divided into two groups: one fed a normal diet (control) and the other fed an iron-restricted diet (IR) for 4 weeks. As compared with control and IR mice, Aldo mice showed an increase in both systolic blood pressure and urinary albumin/creatinine ratio, but these increases were reduced in the Aldo-IR group. In addition, renal histology revealed that Aldo mice exhibited glomerulosclerosis and tubulointerstitial fibrosis, whereas these changes were attenuated in Aldo-IR mice. Expression of intracellular iron transport protein transferrin receptor 1 was increased in the renal tubules of Aldo mice compared with control mice. Dietary iron restriction attenuated the development of hypertension and renal injury in aldosterone/salt-induced hypertensive mice.

Association between renal iron accumulation and renal interstitial fibrosis in a rat model of chronic kidney disease.

Iron accumulation is associated with the pathophysiology of chronic kidney disease (CKD). Renal fibrosis is a final common feature that contributes to the progression of CKD; however, little is known about the association between renal iron accumulation and renal interstitial fibrosis in CKD. Here we investigate the effects of iron chelation on renal interstitial fibrosis in a rat model of CKD. CKD was induced by 5/6 nephrectomy in Sprague-Dawley rats. At 8 weeks after operation, 5/6 nephrectomized rats were administered an oral iron chelator, deferasirox (DFX), in chow for 8 weeks. Other CKD rats were given a normal diet. Sham-operative rats given a normal diet served as a control. CKD rats exhibited hypertension, glomerulosclerosis and renal interstitial fibrosis. Iron chelation with DFX did not change hypertension and glomerulosclerosis; however, renal interstitial fibrosis was attenuated in CKD rats. Consistent with these findings, renal gene expression of collagen type III and transforming growth factor-ß was increased in CKD rats compared with the controls, while iron chelation suppressed these increments. In addition, a decrease in vimentin along an increase in E-cadherin in renal gene expression was observed in CKD rats with iron chelation. CKD rats also showed increased CD68-positive cells in the kidney, whereas its increase was attenuated by iron deprivation. Similarly, increased renal gene expression of CD68, tumor necrosis factor-α and monocyte chemoattractant protein-1 was suppressed in CKD rats with iron chelation. Renal iron accumulation seems to be associated with renal interstitial fibrosis in a rat model of CKD.

Cardiac remodeling in response to chronic iron deficiency: role of the erythropoietin receptor.

OBJECTIVE: Anemia is a common comorbidity of patients with heart failure, and iron deficiency is known as one of the causes of anemia in heart failure. Recent studies have shown that iron deficiency alone, without overt anemia, is associated with poor outcomes in patients with heart failure. Thus, to minimize the mortality in patients with heart failure, it is important to understand the link between iron deficiency and cardiac function. Chronic untreated iron deficiency results in cardiac remodeling, and we have previously reported that erythropoietin (Epo) and cardiac Epo receptor (EpoR) signaling may be associated with its remodeling. However, the link between EpoR signaling and its remodeling remains to be elucidated. Herein, we investigated the role of EpoR signaling on cardiac remodeling in response to chronic iron deficiency. METHODS: Wild-type mice and transgene-rescued EpoR-null mutant mice, which express EpoR only in the hematopoietic lineage (EpoR-restricted mice), were fed with either a normal or an iron-restricted diet, and the molecular mechanisms were investigated. RESULTS: Dietary iron restriction gradually induced anemia, Epo secretion, and cardiac hypertrophy in wild-type mice. In contrast, EpoR-restricted mice fed with an iron-restricted diet exhibited anemia, left ventricular dilatation, and cardiac dysfunction compared with wild-type mice. Interestingly, altered cardiac mitochondrial biogenesis was observed in EpoR-restricted mice following iron deficiency. Moreover, cardiac p53 expression was increased in EpoR-restricted mice compared with wild-type mice following iron deficiency. CONCLUSION: These data indicate that EpoR signaling is associated with cardiac remodeling following chronic iron deficiency.

Hemodynamic response to sildenafil in patients with decompensated congestive heart failure can be predicted by deceleration time of transmitral flow.

AIM: How sildenafil acutely provides hemodynamic alterations in patients with decompensated congestive heart failure remains unknown. The aim of this study was to investigate whether myocardial and/or hemodynamic conditions affect hemodynamic response to sildenafil in patients with decompensated heart failure. METHODS AND RESULTS: Twenty-five consecutive patients with decompensated congestive heart failure were enrolled. The patients underwent echocardiography before and 1 hour after a single oral administration of sildenafil (20 mg). Sildenafil decreased pulmonary vascular resistance by 24% (P < 0.05), and increased left ventricular (LV) time-velocity integral by 17% (P < 0.05). Alteration of the ratio of peak velocity of early LV filling to early diastolic myocardial velocity (E/E'), an indicator of LV filling pressure, following administration of sildenafil, negatively associated with the deceleration time of early filling wave (DcT) at baseline. Patients with baseline DcT ≥ 200 milliseconds (n = 11) exhibited E/E' increase, whereas patients with baseline DcT <200 milliseconds (n = 14) exhibited E/E' decrease. CONCLUSIONS: Administration of sildenafil elevated LV filling pressure in decompensated heart failure patients with shortened deceleration time of early diastolic transmitral flow.

Worsening of proteinuria caused by combination therapy of hypertonic saline and low-dose furosemide for treatment of acute decompensated heart failure with overt diabetic nephropathy.

A combination of hypertonic saline and furosemide has been proposed as a new therapeutic approach for treating acute decompensated heart failure (ADHF). The advantages of this combination have not only been demonstrated in ADHF but also in refractory ascites due to liver cirrhosis. However, the therapeutic effects of this regimen have never been evaluated in ADHF with overt diabetic nephropathy (ODN). Here, we present an interesting case of a 35-year-old patient admitted to our hospital for ADHF with shortness of breath and systemic edema, complicated with hypertension, type 2 diabetes, and ODN. Echocardiography showed left ventricular enlargement and diffuse hypokinesis, with ejection fraction of 33%. Urinary findings showed total proteinuria of 3597 mg/day during the first day of hospitalization. We initiated decongestion therapy with continuous infusion of hypertonic saline and furosemide. In spite of increased diuresis, edema remained the same and serum albumin decreased from 2.7 g/dl to 2.0 g/dl, and proteinuria increased up to 7344 mg/day. The amount of proteinuria and serum albumin level gradually recovered over time after cessation of the therapy. These data suggest that the combination therapy worsens glomerular hypertension and ODN. Therefore, hypertonic saline and furosemide combination therapy should not be recommended for patients with ODN. .

Intravenous salt supplementation with low-dose furosemide for treatment of acute decompensated heart failure.

BACKGROUND: Theoretically, salt supplementation should promote diuresis through increasing the glomerular filtration rate (GFR) during treatment of acute decompensated heart failure (ADHF) even with low-dose furosemide; however, there is little evidence to support this idea. METHODS AND RESULTS: This was a prospective, randomized, open-label, controlled trial that compared the diuretic effectiveness of salt infusion with that of glucose infusion supplemented with low-dose furosemide in 44 consecutive patients with ADHF. Patients were randomly administered 1.7% hypertonic saline solution supplemented with 40 mg furosemide (salt infusion group) or glucose supplemented with 40 mg furosemide (glucose infusion group). Our major end points were 24-hour urinary volume and GFR. Urinary volume was greater in the salt infusion group than in the glucose infusion group (2,701 ± 920 vs 1,777 ± 797 mL; P < .001). There was no significant difference in the estimated GFR at baseline. Creatinine clearance for 24 h was greater in the salt infusion group than in the glucose infusion group (63.5 ± 52.6 vs 39.0 ± 26.3 mL min(-1) 1.73 m(-2); P = .048). CONCLUSIONS: Salt supplementation rather than salt restriction evoked favorable diuresis through increasing GFR. The findings support an efficacious novel approach of the treatment of ADHF.