Preliminary in-silico analysis of vascular graft implantation configuration and surface modification.

Vascular grafts are used to reconstruct congenital cardiac anomalies, redirect flow, and offer vascular access. Donor tissue, synthetic, or more recently tissue-engineered vascular grafts each carry limitations spanning compatibility, availability, durability and cost. Synthetic and tissue-engineered grafts offer the advantage of design optimization using in-silico or in-vitro modeling techniques. We focus on an in-silico parametric study to evaluate implantation configuration alternatives and surface finishing impact of a novel silicon-lined vascular graft. The model consists of a synthetic 3D-generic model of a graft connecting the internal carotid artery to the jugular vein. The flow is assumed unsteady, incompressible, and blood is modeled as a non-Newtonian fluid. A comparison of detached eddy turbulence and laminar modeling to determine the required accuracy needed found mild differences mainly dictated by the roughness level. The conduit walls are modeled as non-compliant and fixed. The shunt configurations considered, are straight and curved with varied surface roughness. Following a grid convergence study, two shunt configurations are analyzed to better understand flow distribution, peak shear locations, stagnation regions and eddy formation. The curved shunt was found to have lower peak and mean wall-shear stress, while resulting in lower flow power system and decreased power loss across the graft. The curved smooth surface shunt shows lower peak and mean wall-shear stress and lower power loss when compared to the straight shunt.

Cardiac resynchronization therapy in patients with postero-lateral scar by cardiac magnetic resonance: A systematic review and meta-analysis.

BACKGROUND: Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in selected patients with heart failure, but up to one third of patients may not respond to CRT. A transmural postero-lateral (TMPL) wall scar in the left ventricle (LV) or over the LV pacing site may attenuate clinical and echocardiographic response to CRT. METHODS AND RESULTS: We systematically searched PubMed, EMBASE, and Cochrane databases for studies examining the association between Cardiac magnetic resonance (CMR)-determined postero-lateral or LV pacing site scar and clinical and echocardiographic response to CRT. Eleven prospective studies were included. The presence of TMPL scar on pre-implant CMR was associated with a 75% lower chance of echocardiographic response to CRT, and a similarly lower chance of clinical response. Significant scar over LV pacing site on pre-implant CMR was also associated with a 46% lower chance of echocardiographic response to CRT, and a 67% lower chance of clinical response. CONCLUSIONS: The presence of transmural postero-lateral scar or significant scar within the LV pacing site detected by pre-implant CMR is associated with a lower rate of clinical or echocardiographic response to CRT.

Rare combination of bilateral divided atrial chambers and pulmonary vein stenosis with review of the literature.

INTRODUCTION: The term cor triatriatum is used to describe a fibromuscular partition that divides an atrium into two compartments. It was first used by Borst in 1905, although the lesion had been described before by Church in 1868. Both described divided left atrial chamber (also referred to as cor triatriatum sinister). The incidence of the divided left atrial chamber among patients with congenital heart disease is reported at 0.1% and 0.4% in an autopsy study. Divided right atrial chamber - also referred to as cor triatriatum dexter - is even rarer to an extent that there is no reported incidence and only few hundred cases have been reported so far. A search through pubMed library revealed only 90 publications on humans, either under the term "dexter" or "dextrum". We would like to report a new association of bilateral divided atrial chambers and pulmonary vein stenosis, with a review of the literature.

Protocol for relative hydrodynamic assessment of tri-leaflet polymer valves.

Limitations of currently available prosthetic valves, xenografts, and homografts have prompted a recent resurgence of developments in the area of tri-leaflet polymer valve prostheses. However, identification of a protocol for initial assessment of polymer valve hydrodynamic functionality is paramount during the early stages of the design process. Traditional in vitro pulse duplicator systems are not configured to accommodate flexible tri-leaflet materials; in addition, assessment of polymer valve functionality needs to be made in a relative context to native and prosthetic heart valves under identical test conditions so that variability in measurements from different instruments can be avoided. Accordingly, we conducted hydrodynamic assessment of i) native (n = 4, mean diameter, D = 20 mm), ii) bi-leaflet mechanical (n= 2, D = 23 mm) and iii) polymer valves (n = 5, D = 22 mm) via the use of a commercially available pulse duplicator system (ViVitro Labs Inc, Victoria, BC) that was modified to accommodate tri-leaflet valve geometries. Tri-leaflet silicone valves developed at the University of Florida comprised the polymer valve group. A mixture in the ratio of 35:65 glycerin to water was used to mimic blood physical properties. Instantaneous flow rate was measured at the interface of the left ventricle and aortic units while pressure was recorded at the ventricular and aortic positions. Bi-leaflet and native valve data from the literature was used to validate flow and pressure readings. The following hydrodynamic metrics were reported: forward flow pressure drop, aortic root mean square forward flow rate, aortic closing, leakage and regurgitant volume, transaortic closing, leakage, and total energy losses. Representative results indicated that hydrodynamic metrics from the three valve groups could be successfully obtained by incorporating a custom-built assembly into a commercially available pulse duplicator system and subsequently, objectively compared to provide insights on functional aspects of polymer valve design.

Right superior vena cava draining in the left atrium associated with tetralogy of Fallot and pulmonary atresia.

We report a case of an anomalous drainage of the right superior vena cava to the left atrium with intact atrial septum associated with Tetralogy of Fallot, pulmonary atresia, and major aortopulmonary collateral arteries.

Use of 320-detector computed tomographic angiography for infants and young children with congenital heart disease.

Pediatric patients with complex congenital heart disease (CHD) face a lifetime of treatment with interventional therapeutic and palliative procedures. Echocardiography remains the mainstay for noninvasive imaging of congenital heart lesions. This often is supplemented with diagnostic cardiac catheterization for additional anatomic and physiologic characterization. However, recent technological improvements in computed tomography (CT) and magnetic resonance imaging (MRI) have led to an increased focus on the use of these techniques given their better safety profile. This study aimed to review the authors' experience with a 320-slice multidetector CT scanner in the evaluation of CHD in children. This retrospective case study investigated 22 infants and young children with a provisional diagnosis of CHD. Their anatomic evaluation was performed using a 320-slice Aquilon ONE CT scanner. Of these 22 patients, 14 were examined without cardiac gating. This was subsequently modified to a prospective gated, targeted protocol to decrease the radiation dose. The images were interpreted by an experienced radiologist and a pediatric cardiologist. Continuous variables were expressed as mean and standard deviation or range, and the two imaging protocols were compared. A comparison of exposure rates with those from other pediatric studies that had used the 64-slice CT angiography also was performed. For the first group of patients, with nongated CT examinations, the mean effective whole-body radiation dose was 1.8 ± 0.71 millisieverts (mSv) (range, 0.96-3.2 mSv). For the second group, the mean was 0.8 ± 0.39 mSv (range, 0.4-1.5 mSv). Although the radiation dose was reduced dramatically, clinicians must be vigilant about the cumulative risk of radiation exposure.

PRX-08066, a novel 5-hydroxytryptamine receptor 2B antagonist, reduces monocrotaline-induced pulmonary arterial hypertension and right ventricular hypertrophy in rats.

Pulmonary arterial hypertension (PAH) is a life-threatening disease that results in right ventricular failure. 5-((4-(6-Chlorothieno[2,3-d]pyrimidin-4-ylamino)piperidin-1-yl)methyl)-2-fluorobenzonitrile monofumarate (PRX-08066) is a selective 5-hydroxytryptamine receptor 2B (5-HT2BR) antagonist that causes selective vasodilation of pulmonary arteries. In the current study, the effects of PRX-08066 were assessed by using the monocrotaline (MCT)-induced PAH rat model. Male rats received 40 mg/kg MCT or phosphate-buffered saline and were treated orally twice a day with vehicle or 50 or 100 mg/kg PRX-08066 for 5 weeks. Pulmonary and cardiac functions were evaluated by hemodynamics, heart weight, magnetic resonance imaging (MRI), pulmonary artery (PA) morphology, and histology. Cardiac MRI demonstrated that PRX-08066 (100 mg/kg) significantly (P < 0.05) improved right ventricular ejection fraction. PRX-08066 significantly reduced peak PA pressure at 50 and 100 mg/kg (P < 0.05 and < 0.01, respectively) compared with MCT control animals. PRX-08066 therapy also significantly reduced right ventricle (RV)/body weight and RV/left ventricle + septum (P < 0.01 and < 0.001, respectively) compared with MCT-treated animals. Morphometric assessment of pulmonary arterioles revealed a significant reduction in medial wall thickening and lumen occlusion associated with both doses of PRX-08066 (P < 0.01). The 5-HT2BR antagonist PRX-08066 significantly attenuated the elevation in PA pressure and RV hypertrophy and maintained cardiac function. Pulmonary vascular remodeling was also diminished compared with MCT control rats. PRX-08066 prevents the severity of PAH in the MCT rat model.

Transient ventricular dysfunction after an asphyxiation event: stress or hypoxia?

OBJECTIVE: This report of a pediatric patient with acute upper airway obstruction causing asphyxiation emphasizes the need to maintain clinical suspicion for acquired myocardial dysfunction, despite the presumed role of noncardiogenic causes for pulmonary edema after an acute upper airway obstruction. DESIGN: Case report. SETTING: A tertiary pediatric intensive care unit. PATIENT: A 10-year-old girl with no significant medical history who developed flash pulmonary edema and acute myocardial dysfunction after an acute upper airway obstruction. INTERVENTIONS: Serial echocardiograms, exercise stress test, and coronary angiography were performed. Serial pro-brain natriuretic peptide, troponins, and CK-MB levels were also followed. RESULTS: Troponin level normalized approximately 7 days after the acute event. CK-MB and pro-brain natriuretic peptide levels decreased but had not completely normalized by time of discharge. The patient was discharged home 10 days after the event on an anticipated 6-month course of metoprolol without any signs or symptoms of cardiac dysfunction. CONCLUSIONS: Myocardial dysfunction is rarely documented in children after an acute upper airway obstruction or an asphyxiation event. Pediatric intensivists and hospitalists should maintain a high degree of clinical suspicion and screen for possible myocardial dysfunction in the pediatric patient with an acute severe hypoxic event especially when accompanied by pulmonary edema. Prompt evaluation ensures appropriate support. Additionally, some role may exist for early adrenergic receptor blockade.