A fluid–structure interaction model of the aortic valve with coaptation and compliant aortic root

While aortic valve root compliance and leaflet coaptation have significant influence on valve closure, their implications have not yet been fully evaluated. The present study developed a full fluid–structure interaction (FSI) model that is able to cope with arbitrary coaptation between the leaflets of the aortic valve during the closing phase. Two simplifications were also evaluated for the simulation of the closing phase only. One employs an FSI model with a rigid root and the other uses a “dry” (without flow) model. Numerical tests were performed to verify the model. New metrics were defined to process the results in terms of leaflet coaptation area and contact pressure. The axial displacement of the leaflets, closure time and coaptation parameters were similar in the two FSI models, whereas the dry model, with imposed uniform load on the leaflets, produced larger coaptation area and contact pressure, larger axial displacement and faster closure time compared with the FSI model. The differences were up to 30% in the coaptation area, 55% in the contact pressure and 170% in the closure time. Consequently, an FSI model should be used to accurately resolve the kinematics of the aortic valve and leaflet coaptation details during the end-closing stage.     

Transapical aortic valve implantation – a rescue procedure for patients with aortic stenosis and “porcelain aorta”

Surgical aortic valve replacement (AVR) still remains the treatment of choice in symptomatic significant aortic stenosis (AS). Due to technical problems, extensive calcification of the ascending aorta (“porcelain aorta”) is an additional risk factor for surgery and transapical aortic valve implantation (TAAVI) is likely to be the only rescue procedure for this group of patients. We describe the case of an 81-year-old woman with severe AS and “porcelain aorta”, in whom the only available life-saving intervention was TAAVI.     

Coronary–aortic interaction during ventricular isovolumic contraction

In earlier work, we suggested that the start of the isovolumic contraction period could be detected in arterial pressure waveforms as the start of a temporary pre-systolic pressure perturbation (AIC_start, start of the Arterially detected Isovolumic Contraction), and proposed the retrograde coronary blood volume flow in combination with a backwards traveling pressure wave as its most likely origin. In this study, we tested this hypothesis by means of a coronary artery occlusion protocol. In six Yorkshire × Landrace swine, we simultaneously occluded the left anterior descending (LAD) and left circumflex (LCx) artery for 5 s followed by a 20-s reperfusion period and repeated this sequence at least two more times. A similar procedure was used to occlude only the right coronary artery (RCA) and finally all three main coronary arteries simultaneously. None of the occlusion protocols caused a decrease in the arterial pressure perturbation in the aorta during occlusion (P > 0.20) nor an increase during reactive hyperemia (P > 0.22), despite a higher deceleration of coronary blood volume flow (P = 0.03) or increased coronary conductance (P = 0.04) during hyperemia. These results show that the pre-systolic aortic pressure perturbation does not originate from the coronary arteries.     

Transforming growth factor-β and abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are common problems in aged people which can be associated with severe complications including aortic rupture and death. Transforming growth factor-β (TGFβ) has been implicated as causative in the development of thoracic aortic aneurysms (TAAs). In contrast, current evidence suggests TGFβ inhibits AAA development. Polymorphisms in the TGFβ signaling components are associated with AAA in some human population studies. In experimental animals TGFβ protects against AAA formation, progression and rupture. In animal models of AAA TGFβ decreases aortic inflammatory cell infiltration, extracellular matrix degradation, and vascular smooth muscle cell apoptosis, all factors implicated in AAA pathogenesis. The TGFβ signaling pathway may provide a therapeutic target for AAA although better clarity is needed regarding the distinct roles of TGFβ in TAA and AAA.     

Higher rate of aortic stenosis progression in patients with bicuspid versus tricuspid aortic valve – A single center experience

PurposeWe sought to investigate aortic stenosis (AS) progression rate (pr) with the comparison between bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) morphology.Materials and methodsWe compared ASpr in patients with BAV and TAV examined by transthoracic echocardiography (TTE) in the years 2004–2019.ResultsData from 363 TTEs in 161 AS patients (median age 70 [61–77] years; 63% men; 25% with BAV; 20% with severe AS) performed at different time points (median time interval 10 months) was analyzed. We assessed changes of AS severity with peak velocity through aortic valve (Vmax), mean/peak pressure gradients (MG/PG), aortic valve area by planimetry and continuity equation (AVAce). We compared pr (defined as parameter change per year) between the BAV and the TAV groups. BAV patients showed faster ASpr with odds ratio 3.467 and 95% confidence intervals 1.36 to 8.86, moreover, expressed as a quicker AVAce decrease 0 (−0.4-0.0) in the BAV vs. 0 (−0.15 – 0.0) cm²/year in the TAV group, p ​= ​0.02. Furthermore, in BAV, female sex was associated with lower ASpr (p ​= ​0.01), and in the whole group a larger aortic diameter was a predictor of faster progression (p ​< ​0.001).ConclusionThe ASpr, expressed as a decrease in the AVAce, was faster in BAV. Moreover, ASpr depends on both: valve morphology being faster in BAV and Vmax increase. Furthermore, the female sex was related to slower pace of AVA reduction in BAV subgroup whereas the larger baseline aortic diameter associated to faster AS progression in the whole studied group.     

Association of the TGF-�� receptor genes with abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a multifactorial condition. The transforming growth factor β (TGF-β) pathway regulates vascular remodeling and mutations in its receptor genes, TGFBR1 and TGFBR2, cause syndromes with thoracic aortic aneurysm (TAA). The TGF-β pathway may be involved in aneurysm development in general. We performed an association study by analyzing all the common genetic variants in TGFBR1 and TGFBR2 using tag single nucleotide polymorphisms (SNPs) in a Dutch AAA case–control population in a two-stage genotyping approach. In stage 1, analyzing 376 cases and 648 controls, three of the four TGFBR1 SNPs and nine of the 28 TGFBR2 SNPs had a P<0.07. Genotyping of these SNPs in an independent cohort of 360 cases and 376 controls in stage 2 confirmed association (P<0.05) for the same allele of one SNP in TGFBR1 and two SNPs in TGFBR2. Joint analysis of the 736 cases and 1024 controls showed statistically significant associations of these SNPs, which sustained after proper correction for multiple testing (TGFBR1 rs1626340 OR 1.32 95% CI 1.11–1.56 P=0.001 and TGFBR2 rs1036095 OR 1.32 95% CI 1.12–1.54 P=0.001 and rs4522809 OR 1.28 95% CI 1.12–1.46 P=0.0004). We conclude that genetic variations in TGFBR1 and TGFBR2 associate with AAA in the Dutch population. This suggests that AAA may develop partly by similar defects as TAA, which in the future may provide novel therapeutic options.     

Heart rate variability in children with aortic valve stenosis – a pilot study

Introduction

The aim of our prospective study was to evaluate heart rate variability (HRV) in children with aortic valve stenosis (AS) and its relationship with left ventricular mass and peak transaortic valve pressure gradient (PG).

Material and methods

Sixty children with AS divided into 3 groups according to their PG and 60 healthy controls were studied. Holter ECG monitoring with time domain HRV analysis was performed. Left ventricular mass was calculated by echocardiography.

Results

Mean values of all HRV parameters were statistically significantly lower (p < 0.001) in children with AS than in controls (respectively: SDNN 127.8 ±28.2 ms; 162.6 ±38.0 ms, SDNN day 99.7 ±26.6 ms; 134.1 ±36.1 ms, SDNN night 99.9 ±32.8 ms; 123.4 ±45.7 ms, SDANN 112.2 ±27.7 ms; 142.4 ±34.6, SDNNi 62.2 ±16.2 ms; 75.9 ±21.6, RMSSD 39.6 ±12.1 ms; 50.3 ±16.7 ms, rMSSD day 33.6 ±10.9 ms; 43.1 ±14.7 ms, rMSSD night 49.8 ±18.1 ms; 64.4 ±24.9 ms, pNN50 16.4 ±9.5%; 23.5 ±11.7%, pNN50 day 12.0 ±8.5%; 18.4 ±10.7%, pNN50 night; 26.5 ±14.8%; 36.4 ±17.4%. No significant differences between the mean values of HRV parameters in children with different PG and with and without myocardial hypertrophy were found. In children with AS and ventricular arrhythmia SDNN day was significantly lower (p < 0.05) compared to patients without arrhythmia (94.9 ±22.1 ms vs. 109.3 ±22.5 ms).

Conclusions

In children with AS the balance of the autonomic nervous systemic disturbed which manifests in an increase in sympathetic and decrease in parasympathetic activity. Transaortic valve pressure gradient and myocardial hypertrophy do not influence the HRV. The SDNN reduction during the day period may indicate the risk of ventricular arrhythmia in children with AS.     

Is a designated arterial catheter indicated in transcatheter aortic valve replacement procedure?

<正>Aortic stenosis(AS) is the most common valvular disorder frequently affecting patients as they get older,and resulting in life-altering symptoms such as dyspnea, angina, pre-syncope, and syncope, which are often made worse with exertion. Often, AS is caused by age-related calcification of the valve;     

Potential complications of transcatheter aortic valve implantation (TAVI)—an autopsy perspective

ObjectiveDegenerative or post-endocarditic destruction of aortic valves with secondary left ventricular hypertension and cardiac insufficiency is seen more frequently in patients of increasing age. When conventional aortic valve replacement is no longer an option, because of age and co-morbidity, patients are increasingly treated with interventional aortic valve replacement using transcatheter aortic valve implantation (TAVI).Methods and resultsTAVI has been performed in Cologne since 2008. We screened our autopsy registry for cases of TAVI, identifying and characterizing complications in connection with the TAVI procedure. We found 13 patients who underwent TAVI procedure. Five of these patients died of non-TAVI specific postoperative complications, whereas in 8 patients there was a direct relationship between TAVI complications and the cause of death. The Patients died within hours and few days after TAVI procedure respectively. Problems observed included predominantly complications due to calcifications of the aortic valve cusps as well as acute endocarditis in 20% of cases. In one case there was an irreversible compression of the implanted valve due to cardiac resuscitation and a malposition of the bioprosthesis.ConclusionsFuture improvements of preoperative evaluation, especially concerning the degree of calcifications of the aortic valve, appear necessary to increase the chance of preventing such complications. Until then, autopsy analysis of complications may help to improve the TAVI procedure.     

Can the intermittent low-speed function of left ventricular assist device prevent aortic insufficiency?

Journal of Artificial Organs - Aortic insufficiency (AI) is known to associate with a persistently closed aortic valve during continuous-flow ventricular assist device support. Some devices carry...     

Twelve-year experience with the Carpentier–Edwards pericardial aortic valve at a single Japanese center

Our aim was to evaluate the long-term results of implantation of the Carpentier–Edwards pericardial (CEP) valve in the aortic position. Between January 1996 and December 2007, 244 patients who underwent aortic valve replacement using the CEP valve were enrolled in this study. A 19-mm valve was used in 39 patients, a 21-mm valve in 94 patients, a 23-mm valve in 81 patients, and a 25-mm valve in 30 patients. The early and the late results were evaluated. Furthermore, echocardiographic examination was performed at follow-up. There were 5 early deaths, with an early mortality rate of 2.0%. Follow-up was performed in 95.4% of the survivors of the operation for a mean period of 4.1 years. Actuarial survival rates at 5, 10, and 12 years were 85.3 ± 2.8, 80.0 ± 3.7 and 70.0 ± 9.8%, respectively. Thromboembolism was observed in 6 patients, endocarditis in 2 patients, reoperation in 4 patients, and structural valve deterioration in 2 patients. Actuarial freedoms from thromboembolism, endocarditis, and reoperation at 10 years were 96.9 ± 0.14, 97.7 ± 0.16, and 97.0 ± 0.16%, respectively. Echocardiographic examination revealed that the pressure gradients across the valve prosthesis for valves of each size were acceptable. Left ventricular mass index decreased significantly in all valve sizes. The long-term results of implantation of the CEP bioprosthesis in the aortic position were satisfactory. The CEP bioprosthesis maintained its hemodynamic performance even as late as 10 years after implantation.     

Use of electrochemical impedance measurements to monitor β-adrenergic stimulation of bovine aortic endothelial cells

 Due to the high permeability of endothelial cell layers derived from macrovascular vessels, precise determination of their barrier function towards ion movement requires refined experimental techniques. We thus cultured bovine aortic endothelial cells (BAEC) directly on thin gold-film electrodes and measured the electrochemical impedance to study their passive electrical properties in general and during β-adrenergic stimulation. Impedance spectra (10–2·10⁶ Hz) of confluent cell monolayers revealed that the electrical characteristics of the cells can be modelled by a simple resistor-capacitor parallel network. Under control conditions the overall resistance of confluent BAEC monolayers was 3.6±0.6 Ω·cm² (n=30) and the capacitance was 0.6±0.1 μF/cm². Both quantities are discussed with respect to morphological characteristics of these cells. Stimulation of BAECs with the synthetic β-adrenoceptor agonist isoproterenol leads to a concentration-dependent, highly specific increase of the cell layer resistance characterized by a concentration for half-maximal response (EC₅₀) of 0.3±0.1 μM. The cell layer capacitance, however, remained unaffected. Using impedance measurements at a single frequency, we analysed the response of BAECs to treatment with isoproterenol in comparison with several chemically unrelated compounds known to stimulate the adenosine 3’,5’-cyclic monophosphate (cAMP)-dependent signal transduction cascade. These studies confirmed that the enhancement of the cell layer resistance after β-adrenergic stimulation is mediated by an increase in intracellular cAMP. Received: 23 September 1998 / Received after revision: 23 November 1998 / Accepted: 28 January 1999     

Antithrombotic therapy – predictor of early and long-term bleeding complications after transcatheter aortic valve implantation

Introduction

Dual antiplatelet therapy (DAPT) – aspirin and clopidogrel – is recommended after transcatheter aortic valve implantation (TAVI) without an evidence base. The main aim of the study was to estimate the impact of antithrombotic therapy on early and late bleeding. Moreover, we assessed the impact of patients’ characteristics on early bleeding and the influence of bleeding on prognosis.

Material and methods

Between 2009 and 2011, 83 consecutive TAVI patients, age 81.1 ±7.2 years, were included. Bleeding complications were defined by the Valve Academic Research Consortium (VARC) scale. The median follow-up was 12 ±15.5 months (range: 1 to 23) and included 68 (81.9%) patients.

Results

Early bleeding occurred in 51 (61.4%) patients. Vitamin K antagonists (VKA) pre-TAVI (p = 0.001) and VKA + clopidogrel early post-TAVI (p = 0.04) were the safest therapies; in comparison to the safest one, peri-procedural DAPT (p = 0.002; p = 0.05) or triple anticoagulant therapy (TAT) (p = 0.003, p = 0.05) increased the risk for early bleeding. Predictors for early bleeding were: clopidogrel pre-TAVI (OR: 4.43, 95% CI: 1.02–19.24, p = 0.04), preceding percutaneous coronary intervention (PCI) (10.08, OR: 95% CI: 1.12–90.56, p = 0.04), anemia (OR: 4.00, 95% CI: 1.32–12.15, p = 0.01), age > 85 years (OR: 5.96, 95% CI: 1.47–24.13, p = 0.01), body mass index (BMI) (OR: 0.86, 95% CI: 0.74–0.99, p = 0.04). Late bleeding occurred in 35 patients (51.4%) on combined therapy, and none on VKA or clopidogrel monotherapy (p = 0.04). Bleeding complications did not worsen the survival.

Conclusions

This study seems to suggest that advanced age, BMI, and a history of anemia increased the risk for early bleeding after TAVI. Clopidogrel pre-TAVI should be avoided; therefore, time of preceding PCI should take into account discontinuation of clopidogrel in the pre-TAVI period. Vitamin K antagonists with clopidogrel seems to be the safest therapy in the early post-TAVI period, similarly as VKA/clopidogrel monotherapy in long-term prophylaxis.     

Surgical repair for abdominal aortic aneurysm concomitant with iliac arterial disease using InterGard? Quadrifurcated

InterGard? Quadrifurcated [InterVascular S.A. (MAQUET Cardiovascular), La Ciotat, France], a knitted quadrifurcated prosthetic graft, is useful to simplify the procedures for patients with abdominal aortic aneurysm concomitant with iliac arterial disease. From March 2008 to April 2010, 59 patients underwent abdominal aortic aneurysm repair in our department. InterGard? Quadrifurcated was used in 22 patients (37.3%). All patients were male with a mean age of 72.1 ± 12.1 years (range from 45 to 90 years). Four were emergency cases. Nineteen patients had common iliac arterial lesions, and 19 patients had internal iliac arterial lesions. In addition to abdominal aortic aneurysm repair, reconstruction of bilateral internal iliac arteries was performed in 4 patients, reconstruction of unilateral internal iliac artery in 15 (right 6, left 9), and internal mesenteric artery in 13. There was one hospital death due to nonocclusive mesenteric infarction. There were two complications, which were intestinal perforation and intestinal obstruction. All of these three cases were emergency cases. Computed tomography scan 1 week after operation showed that all reconstructed grafts were patent. Although patients with abdominal aortic aneurysm concomitant with iliac arterial disease had many preoperative comorbidities, surgical results with InterGard? Quadrifurcated were satisfactory. It is useful to simplify the procedures for these patients.     

Does the additional usage of a local hemostatic patch reduce bleeding after aortic reimplantation?

IntroductionOur study aimed to assess the efficacy of a local hemostatic, consisting of human thrombin and fibrinogen, which was applied on the aortotomy suture line.Material and methodsThe study involved 93 patients undergoing elective aortic valve replacement. Patients were randomized to two groups. Group 1 comprised 41 patients, in whom a hemostatic patch (Tachosil) was used additionally. Group 2 comprised 52 patients in whom Tachosil was not applied.ResultsThe postoperative drainage after 48 h was significantly lower in the group of patients where the local hemostatic patch (Tachosil) was additionally used, compared to the control group (p = 0.0335). The prevalence of rethoracotomies was twice as high in the control group compared to the Tachosil group (5% vs. 10%), but the statistical analysis did not show a significant difference. As a consequence, both measurements of hemoglobin concentration revealed significantly higher hemoglobin in Tachosil-treated patients than the control group (p < 0.001, p = 0.0002). Red blood cell count (RBC) was also significantly higher in the Tachosil group. The difference in perioperative blood loss between the two groups resulted in a difference in postoperative acute renal injury or renal failure. The rate of infection within the early postoperative period was also comparable between the groups, although it was slightly higher in the Tachosil group (23% vs. 18%). The perioperative mortality was higher in group 2 but the difference was not statistically significant (3% in the Tachosil group vs. 5% in the control group).ConclusionsTachosil use reduced postoperative drainage considerably, which had an important influence on renal complications after aortic valve replacement.