Hemodynamic Problems Research Articles

Role of thrombophilia factors in acute systemic-pulmonary shunt obstruction.

Systemic-pulmonary shunts are widely used in initial palliation in cyanotic congenital heart disease. The incidence and the relationship between acute shunt obstruction and thrombophilia are not precisely defined. The aim of this study was to determine the frequency of shunt obstruction in the early postoperative period, and to define the frequency and presence of thrombophilia factors in patients treated for acute shunt thrombosis. Between October 2010 and October 2012, 77 patients who had systemic-pulmonary shunt operation were included in this prospective study. Patients who developed shunt obstruction were examined in terms of inherited and acquired thrombophilia factors. Median patient age was 61 days and median weight was 4.3 kg. Thirty-three patients were neonates. Diameter of the Gore-Tex grafts used for the shunt ranged from 3 mm to 5 mm. Acute shunt occlusion rate was 10% (8/77), and all of these occurred in the first 24 h. Thrombophilia was found in three of eight patients who underwent intervention (surgical and/or transcatheter) due to shunt thrombosis (presence of anti-phospholipid antibodies, n = 1; protein C deficiency, n = 1; and factor V Leiden mutation, n = 1) and only one patient died. Acute shunt obstruction developed in 10% of patients who underwent systemic-pulmonary shunt, and emergency surgery or transcatheter intervention can be life saving in this context. Acute shunt obstruction can occur due to mechanical and hemodynamic problems, but clinicians should also consider and evaluate thrombophilia factors.

A simple modified Bentall technique for surgical reconstruction of the aortic root – short and long term outcomes

BackgroundSince the first introduction of the Bentall technique, several modifications have been proposed to improve patient outcomes and decrease intra- and post-operative complications. We describe a simplified modification of the technique that tries to lessen the intra-operative time, improve homeostasis and miminize early and late complications. Our experience with the technique and short- and long-term patient outcomes are reported.MethodsFrom August 1996 to October 2013, 110 consecutive patients underwent this modified technique. The procedure used Dacron composite graft with a mechanical valve (St. Jude Medical®) for aortic root replacement. To avoid intra-operative complications, no mobilization of coronary ostia was done. Additionally, the tubular aorta was kept minimally unchanged.ResultsTotal bleeding after the operation was 450 ± 105 mL. The mean duration of intensive care unit and hospital stay were 2 ± 1 and 5 ± 2 days, respectively. Sixty-six patients (60 %) were discharged from the surgical intensive care unit on the first postoperative day, 34 patients (30.9 %) were discharged on the second day and ten patients (9.1 %) needed more time to stay in the intensive care unit due to haemodynamic or respiratory problems. At 5-years follow up, survival rate was 97 %. In the three deceased patients, causes of death were mediastinitis, sepsis and myocardial infarction. No operation-related complications such as anticoagulant-related hemorrhage, valve or graft thrombosis, or coronary pseudoaneurysm were occurred during follow-up.ConclusionsThe proposed modification of the Bentall technique seems to minimize late intra-operative blood loss, improves homeostasis, shortens the operation time and is associated with excellent long-term outcomes in patients undergoing composite graft replacement of the aortic root.

On the elasticity of blood vessels in one-dimensional problems of hemodynamics

One-dimensional models of hemodynamics proved to be effective in the analysis of blood flow in humans in the normal and pathological states. A key factor contributing to the successful simulation using one-dimensional models is the inclusion of elastic properties of blood vessel walls. This paper is devoted to the comparative analysis of various mathematical descriptions of elastic properties of vessel walls in modern one-dimensional models of hemodynamics.

Cardiovascular Surgery with Cardiopulmonary Bypass in Patients with Preoperative Non-dialysis Dependent Renal Insufficiency.

Preoperative renal insufficiency is a predictor of acute renal injury in patients undergoing cardiovascular surgery with cardiopulmonary bypass. From January 2010 to September 2012, 121 patients undergoing coronary bypass, valve replacement, or both were included in our retrospective study, using cardiopulmonary bypass. We compared the changes in renal function and clinical outcomes of 66 patients with a baseline serum creatinine level more than 1.5 mg/dL with 55 patients with normal serum creatinine levels. We analyzed the impact of cardiopulmonary bypass in patients with non-dialysis dependent renal insufficiency. In the group of patients with preoperative renal injury, the need for dialysis was greater, time of mechanical ventilation longer, and daily diuresis lesser compared with the group of patients with normal serum creatinine levels. Other clinical outcomes such as postoperative hemodynamic problems and organ dysfunction were similar. Prolonged time of cardiopulmonary bypass and cross-clamp affected postoperative renal injury. The study also showed intraoperative dopamine infusion at renal dose and ultrafiltration are not effective with protecting renal tubular function. Serum creatinine levels and glomerular filtration rate (GFR) were found to be useful parameters for renal injury. These results demonstrate the safety and trustworthiness of cardiopulmonary bypass in patients with non-dialysis dependent renal insufficiency.

Results of Emergency Postoperative Re-Angiography After Cardiac Surgery Procedures

The purpose of this study was to evaluate the diagnostic and therapeutic role of emergency coronary angiography (ECA) in the setting of acute ischemic or hemodynamic instability after cardiac surgery. Between January 2005 and September 2014 we prospectively collected data from a consecutive cohort of 5,275 patients who underwent cardiac surgery. Patients who underwent ECA due to new ST-segment changes on electrocardiogram (ECG), ventricular arrhythmias, cardiac arrest or hemodynamic collapse, new changes in regional wall motion, or any other relevant suspect of myocardial ischemia during postoperative intensive care unit stay were included. Forty patients (0.7% of the overall population) were enrolled. Nineteen patients (47.5%) received isolated coronary surgery, 21 (52.5%) underwent valve or aortic or combined operations. The most common indications to ECA were new ECG or echo signs of acute ischemia (62.5%). The mean time from primary operation to ECA was 51 hours (27 minutes to 9 days). Graft failure was found in 17 cases (42.5%), native coronary artery occlusion in 7 (20%), and coronary spasm in 5 (12.5%). No pathologic alterations were found in 7 cases (17.5%). Three patients (7.5%) underwent reoperation (group 1), 15 (37.5%) underwent percutaneous interventions (PCI) (group 2), and 22 (55%) were managed conservatively (group 3). In-hospital mortality was 100% in group 1, 6% in group 2, and 0% in group 3; 93% of the patients who underwent PCI had complete resolution of the ischemic or hemodynamic problems. No complications related to angiography occurred. Kaplan-Meier survival curves differed significantly according to the post-angiography management. At multivariate analysis combined surgery and the strategy of treatment were independent predictors of long-term mortality. Emergency coronary angiography is safe and allows diagnosis and resolution of the instability in the great majority of cases. An ECA should be the first-line measure in case of acute ischemic or hemodynamic instability after cardiac surgery.

Fluid-structure interaction simulations of cerebral arteries modeled by isotropic and anisotropic constitutive laws

This paper considers numerical simulations of fluid-structure interaction (FSI) problems in hemodynamics for idealized geometries of healthy cerebral arteries modeled by both nonlinear isotropic and anisotropic material constitutive laws. In particular, it focuses on an anisotropic model initially proposed for cerebral arteries to characterize the activation of collagen fibers at finite strains. In the current work, this constitutive model is implemented for the first time in the context of an FSI formulation. In this framework, we investigate the influence of the material model on the numerical results and, in the case of the anisotropic laws, the importance of the collagen fibers on the overall mechanical behavior of the tissue. With this aim, we compare our numerical results by analyzing fluid dynamic indicators, vessel wall displacement, Von Mises stress, and deformations of the collagen fibers. Specifically, for an anisotropic model with collagen fiber recruitment at finite strains, we highlight the progressive activation and deactivation processes of the fibrous component of the tissue throughout the wall thickness during the cardiac cycle. The inclusion of collagen recruitment is found to have a substantial impact on the intramural stress, which will in turn impact the biological response of the intramural cells. Hence, the methodology presented here will be particularly useful for studies of mechanobiological processes in the healthy and diseased vascular wall.

ILU Preconditioners for Nonsymmetric Saddle-Point Matrices with Application to the Incompressible Navier--Stokes Equations

Motivated by the numerical solution of the linearized incompressible Navier--Stokes equations, we study threshold incomplete LU factorizations for nonsymmetric saddle-point matrices. The resulting preconditioners are used to accelerate the convergence of a Krylov subspace method applied to finite element discretizations of fluid dynamics problems in three space dimensions. The paper presents and examines an extension for nonsymmetric matrices of the Tismenetsky--Kaporin incomplete factorization. It is shown that in numerically challenging cases of higher Reynolds number flows one benefits from using this two-parameter modification of a standard threshold ILU preconditioner. The performance of the ILU preconditioners is studied numerically for a wide range of flow and discretization parameters, and the efficiency of the approach is shown if threshold parameters are chosen suitably. The practical utility of the method is further demonstrated for the haemodynamic problem of simulating blood flow in a right c...

PS-096 Feasibility And Safety Of Ductal Closure Using Amplatzer Pda Occluder Ado Iias In Newborn Less Than 2500 Grams

<h3>Objective</h3> To evaluate feasibility and safety of patent ductus arteriosus (PDA) occlusion in very low birth weight newborns &lt; 2500 g when surgery was indicated by PDA occluder under X ray and ultrasounds <h3>Methods</h3> After ultrasound evaluation and Ibuprofen treatment when required, significant haemodynamic PDA were defined by high flow in pulmonary artery branch &gt;45 cm/sec, absence or reverse flow in middle cerebral artery, renal and mesenteric arteries, left to right shunt, and DA diameter. Interventional catheterism was proposed as first option. Babies were anaesthetised with ketamine and sufenta. Femoral vein access by 4F Desilets. A catheter was positionned in descending thoracic aorta and the PDA II AS occluder positionned under horizontal X ray and ultrasound. Temperature was kept between 35.5 and 36°C along the procedure. <h3>Results</h3> Twelve newborns had a PDA closure. Mean weight was 1740 g (850–2480). The series started at the highest weight. Mean diameter of the duct was 3,3 mm (2,2–4) and length 6 (2–11). PDA ADO IISA used were 3 × 4(2) 4 × 2(1), 4 × 4(4), 4 × 6(2), 5 × 2(2) and 5 × 6(1). Two were repositioned. Mean duration of the entire procedure was 32 min (10–90). X ray exposure was 12 min (3–24) and dose 1,5 grey/cm2 (0.2–4). Two transitional paraprothetic shunts closed spontaneously after few days. One premature infant already in renal failure, died ten days later despite ductal closure. In the others the follow up showed improvement in cerebral and pulmonary blood flows without any haemodynamic problems such as observed after surgical procedures. <h3>Conclusion</h3> This preliminary series showed feasibility and safety when combining X-ray and US to close a PDA with PDA ADO IIAS.

Feasibility and safety of closure Patent Ductus Arteriosus (PDA) in premature infants using Amplatzer PDA occluder ADOIIAS

Interventional catheterism can be an alternative to surgery for PDA closure. With the new device PDA ADO IISA, we evaluate feasibility and safety to close PDA in low birth weight infants < 2500 g when indicated. In presence of Clinical signs, ultrasounds (US) defined hemodynamic significant PDA (HSPDA) by mean arterial velocity into pulmonary artery branch > 45 cm/sec, absence or reverse flow in the middle cerebral artery, renal and mesenteric arteries and DA diameter. Interventional catheterism was proposed vs. surgery to the parents. Babies are anesthetized and intubated. The procedure is done under fluoroscopy without contrast and US. Through femoral vein access a 4F catheter is positioned in descending aorta and occluder precisely opened under horizontal X-ray and US. Temperature is kept > 36 °C during the procedure. fourteen infants had PDA closure. Mean weight was 1674 g (880–2480), the series started at the highest weight. Mean diameter of the duct was 3,3 mm (2,2–4) and length 5,8 mm (2–11). PDA ADO IISA used were 3 × 4 (2) 4 × 2 (2), 4 × 4 (4), 4 × 6 (2), 5 × 2 (3) and 5 × 6 (1). Two were repositioned and one changed to increase diameter. Mean duration of the entire procedure was 29 minutes (10–90). X-ray exposure was 12 min (3–24) and dose 1,5 gray/cm 2 (0.2–4). Two transitional paraprothetic shunts closed spontaneously after few days. One premature infant already in renal failure, died ten days later despite ductal closure. In the others, the follow-up showed improvement in cerebral and pulmonary blood flows without any hemodynamic problems such as observed after surgical procedures. This preliminary series showed feasibility and safety when combining X-ray and US to close a PDA with PDA ADO IIAS.

Strukturierte, zeiteffiziente und therapieorientierte Ultraschalldiagnostik bei Dialyseshuntproblemen

Background and aimsA good shunt function without negative effects on the patient is the main priority of shunt surgery. The main shunt problems, e.g. shunt flow too low, peripheral ischemia, arm swelling and shunt infection, necessitate a differential diagnostic approach to clarify the often complex hemodynamic problem as a purely morphological view is often insufficient to deal with the shunt problem.Material and MethodsA structured, time-efficient and therapy-oriented ultrasonography diagnostics is described based on the current literature and own experience.Results and conclusionsDuplex Doppler ultrasonography is a valid method in the diagnostics of shunt-associated problems and shunt stenoses. A structured approach with analysis of the selectively derived Doppler frequency spectrum from the artery feeding the shunt in front of the shunt anastomosis and the artery immediately distal to the anastomosis, with and without manual shunt compression as well as the arteriovenous fistula shortly after the anastomosis allows a targeted sonographic search for the morphological or hemodynamic pathology under appraisal of the clinical shunt problem. The examination can be performed with a very high accuracy in less than 10 minutes.

Research in hemodynamics and cardiac function evaluation of preterm infants

Cardiac dysfunction in preterm infants is a common acute and critical illness,associated with higher mortality,and can cause severe short-term and long-term sequelae. Therefore,understanding the main feature of hemodynamics in premature neonates,and the accurate and appropriate clinical monitoring methods are essential to assess cardiac function in early time. This review summarizes the main hemodynamic problem and cardiac function assessment methods in preterm neonates. Key words: Preterm infants; Hemodynamics; Cardiac function

How to Construct a 3D Mathematical/Computer Model of the Left Ventricle

1. Background In a great many problems the microscopic structure of matter can be disregarded and a biological body replaced by a continuous mathematical model whose geometrical points are identified with material points of the body. The learning of such models is in the province of the me- chanics of continuous media, which covers a vast range of problems in elasticity, hemodynamics, aerodynamics, plasticity, and electrodynamics. When the relative posi- tion of points in a continuous biological body is altered, we say that the body is strained. The change in the rela- tive position of a point is a deformation, and the study of deformations is the region of the analysis of strain. In this paper, the left ventricular myocardium is taken as a biological elastic body and modeled by mathematical/ imaging techniques (1-8).

A modular, operator‐splitting scheme for fluid–structure interaction problems with thick structures

SUMMARYWe present an operator‐splitting scheme for fluid–structure interaction (FSI) problems in hemodynamics, where the thickness of the structural wall is comparable to the radius of the cylindrical fluid domain. The equations of linear elasticity are used to model the structure, while the Navier–Stokes equations for an incompressible viscous fluid are used to model the fluid. The operator‐splitting scheme, based on the Lie splitting, separates the elastodynamics structure problem from a fluid problem in which structure inertia is included to achieve unconditional stability. We prove energy estimates associated with unconditional stability of this modular scheme for the full nonlinear FSI problem defined on a moving domain, without requiring any sub‐iterations within time steps. Two numerical examples are presented, showing excellent agreement with the results of monolithic schemes. First‐order convergence in time is shown numerically. Modularity, unconditional stability without temporal sub‐iterations, and simple implementation are the features that make this operator‐splitting scheme particularly appealing for multi‐physics problems involving FSI. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Assessing Ventricular Scar in Tetralogy of Fallot

The prevalence of repaired congenital heart disease is increasing, and late mortality is an important clinical concern. Patients with tetralogy of Fallot (TOF) contribute the largest fraction of subjects in many articles that address late mortality.1–3 Multicenter studies and single-center groups have mined their databases for retrospective analyses in patients with TOF. These studies have tried to determine which interventions can alter the long-term course of the disease and when these interventions should be performed.4–6 In 2013, we know more about the long-term outcomes in TOF than in any other form of severe congenital heart disease. We have both surgical and catheter-based valve approaches to alter the major long-term hemodynamic problems. It would seem that if we can assist anyone with severe adult congenital heart disease, in TOF we stand on the tallest shoulders and might see the farthest. Article see p 905 For these reasons, we would hope to have the best success at treating ventricular tachycardia (VT) in this population. Antiarrhythmic medications and defibrillator therapies are offered to those patients with the highest risk of life-threatening VT. Ablation serves as a useful adjunct therapy, either to prevent future arrhythmia or to reduce implantable cardioverter-defibrillator shocks. In this issue of Circulation: Arrhythmia and Electrophysiology , Moore et al7 report the results of gross and microscopic evaluation from 27 postmortem specimens with TOF. The authors’ goal was to describe the dimensions of the right ventricular muscular isthmuses and quantify the degree of fibrosis. These isthmuses are narrow bands of conducting muscle; they are anatomically defined by features of the ventricle and by postsurgical scar. These isthmuses help …

Inverse problems in 1D hemodynamics on systemic networks: A sequential approach

In this work, a sequential approach based on the unscented Kalman filter is applied to solve inverse problems in 1D hemodynamics, on a systemic network. For instance, the arterial stiffness is estimated by exploiting cross-sectional area and mean speed observations in several locations of the arteries. The results are compared with those ones obtained by estimating the pulse wave velocity and the Moens-Korteweg formula. In the last section, a perspective concerning the identification of the terminal models parameters and peripheral circulation (modeled by a Windkessel circuit) is presented.

N-Terminal Pro-B-Type Natriuretic Peptide and Its Relationship With Cardiac Function in Adults With Congenital Heart Disease

The aim of this study was to determine the value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in adults with congenital heart disease (CHD) and investigate its relationship with ventricular function and exercise capacity. NT-proBNP may detect early deterioration in cardiac function. In this cross-sectional study, extensive echocardiography, exercise testing, and NT-proBNP measurements were performed on the same day in consecutive adult patients with CHD. In total, 475 patients were included in this study (mean age of 34 ± 12 years, 57% male, 90% New York Heart Association class I). The median NT-proBNP level was 15.1 pmol/l (interquartile range [IQR]: 7.1 to 31.3 pmol/l), and the NT-proBNP level was >14 pmol/l in 53% of patients. The highest NT-proBNP levels were observed in patients with Fontan circulation (36.1 pmol/l [IQR: 14.4 to 103.8 pmol/l]) and a systemic right ventricle (RV) (31.1 pmol/l [IQR: 21.8 to 56.0 pmol/l]), and the lowest values were seen in patients with aortic coarctation (7.3 pmol/l [IQR: 2.8 to 19.5 pmol/l]). NT-proBNP levels correlated with age (r = 0.39, p < 0.001) and were higher in women (median of 21.7 vs. 10.4 pmol/l; p < 0.001). In patients with aortic stenosis or aortic coarctation, NT-proBNP levels correlated with diastolic function parameters of E/E' ratio (r = 0.40, p < 0.001) and left atrial dimension (r = 0.36, p < 0.001). In patients with a systemic RV, NT-proBNP levels correlated with RV annulus diameter (r = 0.31, p = 0.024). In patients with tetralogy of Fallot, the strongest correlations were observed with left atrial dimension (r = 0.46, p < 0.001) and left ventricular ejection fraction (r = 0.37, p < 0.001). NT-proBNP levels were associated with exercise capacity (n = 198) (maximum workload: β = -0.08, p = 0.021) and peak oxygen uptake (β = -0.012, p = 0.011) in a multivariable regression model adjusted for age and sex. NT-proBNP levels in adults with CHD clearly differ by diagnosis and are related to echocardiographic parameters and exercise capacity. Disease-specific correlations contribute to the understanding of the main hemodynamic problems per diagnosis. Follow-up data are needed to elucidate the additional prognostic value.

Computer Modeling to Tailor Therapy for Congenital Heart Disease

The inherent structural and physiological complexity of congenital heart disease lends itself strongly to simulation. Complex hemodynamic and structural problems unique to congenital heart disease may be difficult to understand and the response to therapy or intervention uncertain. Methodologies borrowed from engineering, computing and mathematical sciences can be applied to such problems and used to inform clinical decisions. Therapy thus informed by modeling experiments has the potential to contribute significantly to improved clinical outcomes. This field remains in its infancy, and will only become used routinely if validation of current methods is carried out in the clinical setting.

A reduced computational and geometrical framework for inverse problems in hemodynamics

The solution of inverse problems in cardiovascular mathematics is computationally expensive. In this paper, we apply a domain parametrization technique to reduce both the geometrical and computational complexities of the forward problem and replace the finite element solution of the incompressible Navier-Stokes equations by a computationally less-expensive reduced-basis approximation. This greatly reduces the cost of simulating the forward problem. We then consider the solution of inverse problems both in the deterministic sense, by solving a least-squares problem, and in the statistical sense, by using a Bayesian framework for quantifying uncertainty. Two inverse problems arising in hemodynamics modeling are considered: (i) a simplified fluid-structure interaction model problem in a portion of a stenosed artery for quantifying the risk of atherosclerosis by identifying the material parameters of the arterial wall on the basis of pressure measurements; (ii) a simplified femoral bypass graft model for robust shape design under uncertain residual flow in the main arterial branch identified from pressure measurements.

Pulmonary Hypertension and the Interdependence of Ventricular Function

Pulmonary hypertension is a hemodynamic problem that can result in grave morbidity and mortality, including right-sided heart failure and sudden death. The nature of the pulmonary circulation makes it highly interdependent with right ventricular function. Thus, the study of functional deterioration in pulmonary blood flow should always take into account the impact on right ventricular function, and vice versa. In this article, a comprehensive discussion of the pathophysiology, monitoring, and diagnosis is provided for the complicated disorder of pulmonary hypertension.

Pulmonary Hypertension and the Interdependence of Ventricular Function

Pulmonary hypertension is a hemodynamic problem that can result in grave morbidity and mortality including right-sided heart failure and sudden death. The nature of the pulmonary circulation makes it highly interdependent with right ventricular function. Thus, the study of functional deterioration in pulmonary blood flow should always take into account the impact on right ventricular function, and vice versa. A rational approach to the management of pulmonary hypertension should focus not only on specific dynamics of that low pressure circuit but also on enhancing the function of the right ventricle. In this article, a comprehensive discussion of recent developments in pharmacologic and surgical therapies is provided for the complicated disorder of pulmonary hypertension.