Velocity vector imaging for the assessment of segmental ventricular function in children with a single right ventricle after cavopulmonary anastomosis.

OBJECTIVE: Ventricular function assessment is very important for the treatment and prognostic classification of children with a single right ventricle (SRV) after cavopulmonary anastomosis (CPA). However, unusual ventricular shapes can result in inaccurate measurements. The aim of this study was to evaluate velocity vector imaging (VVI) for assessing segmental ventricular function in children with SRV after CPA. METHODS: Twenty-one children with SRV after CPA and 21 age- and sex-matched children with normal biventricular anatomy and function were included. The longitudinal velocity, displacement, strain and strain rate were measured in the two groups in six segments by VVI. The velocity, displacement, strain and strain rate of the SRVs were compared with max(dp/dt) measured during simultaneous cardiac catheterization in the SRV subjects. RESULTS: The control group consisted of 13 males and 8 females (69% males) with a mean age of 6.7 ± 3.5 years and mean weight of 20.5 ± 6.5 kg, and the study group consisted of 13 males and 8 females with a mean age 6.7 ± 3.7 years and mean weight of 20.6 ± 6.8 kg. Age, weight and sex distribution were similar between the groups (all, p > .05). Strain and strain rate values in all six segments were significantly lower in the study group than in the control group (all, p < .05). The max(dp/dt) of the SRV was 522.84 ± 158.32 mmHg/s, and the strain rate of the basal segment at the rudimentary chamber correlated best with max(dp/dt) (r = 0.74, p < .01). CONCLUSIONS: Segmental ventricular dysfunction was present in children with SRV after CPA, and it could be assessed using VVI.

Three-dimensional rotational angiography in the assessment of vascular and airway compression in children after a cavopulmonary anastomosis.

The aim of the study was to examine the role of three-dimensional rotational angiography (3DRA) in assessing vascular and airway narrowing in children with a bidirectional cavopulmonary anastomosis (BCPA). The course of children with single ventricle physiology is often complicated by left pulmonary artery (LPA) and/or bronchial stenosis and may be related to aortic compression. 3DRA may be useful in evaluating this complex anatomy and possible mechanisms for the observed obstruction. Clinical data and imaging (2D angiography and 3DRA) of children with a BCPA were reviewed retrospectively. Measurements were taken at similar locations along the pulmonary arteries in both modalities and in the airways on 3DRA. Twenty-five children with a previous BCPA were assessed at mean age of 3.1 ± 2.0 years and weight of 13.6 ± 3.6 kg. Excellent correlation was found between 3DRA and 2D angiographic LPA measurements (r = 0.89, p < 0.0001). Twelve children had qualitative LPA stenosis on 3DRA, with a stenotic dimension of 6.6 ± 2.2 mm on 2D angiography and 6.8 ± 1.9 mm on 3DRA (r = 0.94, p < 0.0001). Ten cases with LPA stenosis also had bronchial stenosis (83 %). Qualitative airway assessment correlated with quantitative bronchial dimensions from 3DRA-derived tomographic images: Bronchial stenosis measured 4.4 ± 1.6 versus 5.9 ± 1.1 mm in those with a normal appearing bronchus (p = 0.009). Hybrid patients (initial palliation with bilateral pulmonary artery banding and arterial ductal stenting, n = 5) and all patients with a Damus-Kaye-Stansel (DKS) anastomosis (n = 9) were more likely to have LPA and left bronchial stenosis (OR 7.7, p = 0.04). 3DRA is a useful and accurate tool in assessment of LPA and airway narrowing after BCPA. Hybrid and DKS patients are more prone to LPA and bronchial stenosis, and 3DRA can provide insight into the mechanism.

Anatomical and functional assessment of the intra-atrial lateral tunnel in the Fontan circulation.

OBJECTIVES: In patients after completion of the total cavopulmonary connection (TCPC) with an intra-atrial lateral tunnel, deviations of the tunnel from an ideal straight tubular shape were observed. However, little is known about frequency and adverse effects of such shape deviations. We sought to analyse tunnel anatomy, dimensions and blood flow using cardiac magnetic resonance imaging (CMR). METHODS: Fifty-four patients with hypoplastic left heart syndrome (HLHS; mean age 6.0 ± 2.4 years) underwent CMR with gradient-echo cine sequences, 2D- and 3D-phase-contrast imaging. We analysed anatomy, diameters, cross-sectional areas, volumes and blood flow of the tunnel. RESULTS: Twenty-five patients had a tubular tunnel. In 29 patients, bulging and/or narrowing of the tunnel were present. Cross-sectional areas and volumes of the tunnel were not significantly different between the two groups. There were also no differences for the mean blood flow and the mean and maximal flow velocity (P = 0.05-0.6). In all the patients, the normalized tunnel volume was related to age (r = 0.44; P = 0.002) and body surface area (BSA; r = 0.42; P = 0.005). The mean tunnel blood flow correlated with age (r = 0.73; P = 0.001) and BSA (r = 0.83; P < 0.0001). CONCLUSIONS: A considerable percentage of patients with an intra-atrial lateral tunnel develop mild deviations of the tunnel from ideal tubular shape. The correlation between tunnel volume and mean blood flow with age and BSA suggests that the capacity of the tunnel adjusts to body growth, independent of tunnel shapes that deviate from a fluid-dynamically favourable shape. Follow-up CMRs are needed to detect long-term effects of irregular tunnel shapes on flow dynamics.

Sildenafil and ventriculo-arterial coupling in Fontan-palliated patients: a noninvasive echocardiographic assessment.

The fundamental role of pulmonary vascular resistance in the Fontan circulation is obvious. Medications decreasing this resistance may have an impact on the fate of this population. Hence, we assessed noninvasively the effect of oral sildenafil on the ventriculo-arterial coupling in patients with Fontan circulation. In a single-center, prospective case series study, 23 patients with fenestrated extracardiac total cavopulmonary connection age 12-31 years were enrolled in this study. Clinical characteristics and echocardiographic examination were performed before and after a 1 week course of sildenafil at 0.5 mg/kg every 8 h. Sildenafil had no effect on heart rate and blood pressure. However, oxygen saturation was significantly increased with sildenafil (87.6 ± 4.3 vs. 90.1 ± 3.6; P < 0.0001). The calculated noninvasive ventricular end-systolic elastance (Ees) was greater after sildenafil compared with the pre-sildenafil values (1.59 ± 0.17 vs. 1.72 ± 0.27 mm Hg/ml; P = 0.001). Moreover, significant decreases in arterial elastance (Ea) (1.62 ± 0.53 vs. 1.36 ± 0.43 mm Hg/ml; P < 0.0001), ventricular end-diastolic elastance (Eed) (0.05 ± 0.021 vs. 0.04 ± 0.013; P = 0.002), and, finally, ventriculo-arterial coupling index (0.99 ± 0.26 vs. 0.76 ± 0.15; P < 0.0001) were found after sildenafil administration. The intolerable side effects that led to stopping the sildenafil occurred only in one (4 %) patient. Sildenafil has increased ventricular systolic elastance and improved ventriculo-arterial coupling in patients palliated with Fontan circulation. Short-term sildenafil was well tolerated in most of the patients with only minor side effects.

Performance of a 3-bladed propeller pump to provide cavopulmonary assist in the failing Fontan circulation.

PURPOSE: We hypothesized that a propeller pump design would function optimally to provide cavopulmonary assist in a univentricular Fontan circulation. DESCRIPTION: The hydraulic and hemolysis performance of a rigid three-bladed propeller prototype (similar to a folding propeller design) was characterized. Pressure and flow measurements were taken for flow rates of 0.5 to 3 liters per minute (LPM) for 5,000 to 7,000 revolutions per minute (RPM) using a blood analog fluid. Hemolysis testing was performed using fresh bovine blood for 2 LPM at 6,000 RPM for a 6-hour duration. EVALUATION: The prototype performed well over the design operating range by producing a pressure rise of 5 to 50 mm Hg. Plasma free hemoglobin concentration remained less than 15 mg/dL. The normalized index of hemolysis peaked during the first hour, and then remained less than 10 mg/dL thereafter. CONCLUSIONS: A propeller pump has the pressure-flow characteristics and minimal risk of hemolysis and venous pathway obstruction which make it ideal for temporary cavopulmonary assist. This type of device has the potential to provide a new therapeutic option for patients with failing univentricular Fontan physiology as a bridge-to-recovery or transplantation.

New technique of right heart bypass in congenital heart surgery with autologous lung as oxygenator.

BACKGROUND: Modifications have been made in cardiopulmonary circuit to reduce the inflammatory deleterious effects and cost. We present our experience of one such right heart bypass (RHB) circuit utilizing autologus lung as oxygenator. METHODS: From September 2001 to December 2002, 15 patients underwent congenital heart surgery with this technique. Bypass circuit consisted of a reservoir and a roller pump along with a cardiotomy sucker. The left pulmonary artery and main pulmonary artery were used for arterial return, and venous drainage was achieved with innominate vein cannulation. Inferior vena cava cannulation was performed when needed. Thirteen patients underwent bidirectional Glenn shunt surgery (12 to 24 months, 6 to 10 kg). One patient (26 years old) underwent central shunt with enlargement of confluence and left pulmonary artery. Another patient (18 months old) underwent 1.5 ventricle repair. RESULTS: There were no hospital deaths. Mean flow achieved on RHB was 0.57 +/- 0.3 L/min/m(2), central venous pressure was 3.3 +/- 1.8 mm Hg (0 to 7 mm Hg), and mean arterial pressure could be maintained satisfactorily in all patients (54 +/- 14 mm Hg). Mean RHB time was 54 +/- 14 min. Mean central venous pressure was 10.1 +/- 2.4 mm Hg after procedure and saturation was similar to that on (RHB 88% +/- 8%). The mean amount of drainage was 9.1 +/- 4.2 mL/kg per 24 hours. Avoiding an oxygenator and reducing the number of tubings achieved a combined cost savings of 40% for all procedures. CONCLUSIONS: Right heart bypass is a simple, safer, and less expensive alternative to conventional cardiopulmonary bypass. This technique allows effective decompression of superior vena cava, adequate oxygenation, and predicts saturation after Glenn shunt. It can also be applied for central shunts and pulmonary artery reconstructions with cost containment.

The effects of different mesh generation methods on computational fluid dynamic analysis and power loss assessment in total cavopulmonary connection.

The flow field and energetic efficiency of total cavopulmonary connection (TCPC) models have been studied by both in vitro experiment and computational fluid dynamics (CFD). All the previous CFD studies have employed the structured mesh generation method to create the TCPC simulation model. In this study, a realistic TCPC model with complete anatomical features was numerically simulated using both structured and unstructured mesh generation methods. The flow fields and energy losses were compared in these two meshes. Two different energy loss calculation methods, the control volume and viscous dissipation methods, were investigated. The energy losses were also compared to the in vitro experimental results. The results demonstrated that: (1) the flow fields in the structured model were qualitatively similar to the unstructured model; (2) more vortices were present in the structured model than in the unstructured model; (3) both models had the least energy loss when flow was equally distributed to the left and right pulmonary arteries, while high losses occurred for extreme pulmonary arterial flow splits; (4) the energy loss results calculated using the same method were significantly different for different meshes; and (5) the energy loss results calculated using different methods were significantly different for the same mesh.

Evaluación de las complicaciomes de los diferentes bypass del ventrículo derecho por ecocardiografía con contraste / Assessment of the complications of different types of right ventricular by-pass by means of contrast echocardiography

Mediante ecocardiografía 2-D con contraste, por inyección venosa superior rápida de solución salina agitada (3 cc, < 20 kg y 6 cc, > 20 kg), se estudiaron 54 pacientes con diferentes bypass del ventrículo derecho, para detectar circulación colateral veno-venosa en bypass parcial y total, y cortocircuitos de derecha a izquierda en bypass total. Cuarenta y tres pacientes tenían bypass parcial: 29 tenían una anastomosis cavopulmonar bidireccional con flujo pulmonar adicional (anastomosis sistémica-pulmonar y/o flujo anterógrado ventricular restrictivo); 10 pacientes con corrección biventricular parcial, i.e., anastomosis cavopulmonar bidireccional y flujo anterógrado ventrícular no restrictivo; 2 con Glenn clásico; 2 con operación de Kawashima, i.e., anastomosis cavopulmonar bidireccional en interrupción de vena cava inferior y 11 estaban con bypass total: 10 con anastomosis atriopulmonar y 1 con anastomosis cavopulmonar total. Las edades oscilaban entre 2.5 y 33 años (promedio: 12.2 años) y el periodo de evolución postoperatorio medio fue de 4.3 años. Circulación colateral veno-venosa: 32/43 pacientes (74 por ciento) con bypass parcial; más frecuentemente sin corrección biventricular parcial: 29/33 pacientes (88 por ciento) con respecto a los que tenían corrección biventricular parcial (3/10, 30 por ciento; p < 0.01). Fístulas arteriovenosas del pulmón: 6/43 pacientes (14 por ciento) con bypass parcial; 6/33 (18 por ciento) sin corrección biventricular parcial, 0/10 con corrección biventricular parcial y 0/11 con bypass total. Cortocircuito de derecha a izquierda: 2/11 pacientes (18 por ciento) con bypass total, todos con anastomosis atriopulmonar. La ecocardiografía con contraste es un excelente método de estudio ni invasivo para valorar inicialmente disfunciones específicas de los diferentes bypass del ventrículo derecho. Se resalta la frecuencia de la CCVV en la anastomosis cavopulmonar bidireccional, causa seguramente de la disfunción con hipoxia progresiva en la evolución de estos pacientes. Las fístulas arteriovenosas del pulmón solamente se detectaron en bypass parcial (p < 0.01). Se considera que la menor frecuencia de estas fístulas en anastomosis cavopulmonar bidireccional hallada en este trabajo puede deberse a que fueron efectuadas con flujo pulmonar adicional