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Giardini A.,Cardiorespiratory Unit | Tacy T.A.,University of California at San Francisco
Echocardiography | Year: 2010

Aims: This investigation sought to discern the accuracy of Doppler predictions of pressure drops in stenotic jets mimicking aortic coarctation (AC) across a broad spectrum of conditions, using an in vitro nonpulsatile flow model. Methods and results: The model allowed for different AC diameter and length, different cardiac output, and different diameter of the aorta distal to the AC. For each study condition, pressure drops across a model of AC were measured both noninvasively using the simplified Bernoulli equation (SBE) and invasively using the instantaneous actual pressure gradient. We observed a good correlation of SBE-predicted and actual pressure gradients (slope = 0.929; r = 0.907, P < 0.0001) when AC diameter was small and the diameter of the aorta distal to the AC was large. However, we observed various degrees of overestimation by Doppler when mild AC was simulated (P = 0.0003), or when the diameter of the aorta distal to the coarctation was reduced (P < 0.0001). Increased AC length was associated with underestimation of actual pressure gradient by Doppler when AC diameter was small. Accounting for pressure recovery and viscous losses reduced the discrepancies between Doppler-predicted and actual pressure gradients in all study conditions (slope = 0.964; r = 0.989, P < 0.0001). Conclusions: Caution should be used in applying the SBE to the noninvasive assessment of AC severity. Significant segmental stenosis is associated with significant underestimation of the actual pressure gradient because of viscous losses. A substantial overestimation of the actual pressure drop due to a pressure recovery effect may occur in mild AC, especially when the distal aorta is not dilated. © 2009, Wiley Periodicals, Inc. Source


Steeden J.A.,University College London | Pandya B.,University College London | Tann O.,Cardiorespiratory Unit | Muthurangu V.,University College London
Journal of Cardiovascular Magnetic Resonance | Year: 2015

Background: Contrast enhanced magnetic resonance angiography (MRA) is generally performed during a long breath-hold (BH), limiting its utility in infants and small children. This study proposes a free-breathing (FB) time resolved MRA (TRA) technique for use in pediatric and adult congenital heart disease (CHD). Methods: A TRA sequence was developed by combining spiral trajectories with sensitivity encoding (SENSE, x4 kx-ky and x2 kz) and partial Fourier (75% in kz). As no temporal data sharing is used, an independent 3D data set was acquired every ~1.3s, with acceptable spatial resolution (~2.3x2.3x2.3mm). The technique was tested during FB over 50 consecutive volumes. Conventional BH-MRA and FB-TRA data was acquired in 45 adults and children with CHD. We calculated quantitative image quality for both sequences. Diagnostic accuracy was assessed in all patients from both sequences. Additionally, vessel measurements were made at the sinotubular junction (N = 43), proximal descending aorta (N = 43), descending aorta at the level of the diaphragm (N = 43), main pulmonary artery (N = 35), left pulmonary artery (N = 35) and the right pulmonary artery (N = 35). Intra and inter observer variability was assessed in a subset of 10 patients. Results: BH-MRA had significantly higher homogeneity in non-contrast enhancing tissue (coefficient of variance, P <0.0001), signal-to-noise ratio (P <0.0001), contrast-to-noise ratio (P <0.0001) and relative contrast (P = 0.02) compared to the FB-TRA images. However, homogeneity in the vessels was similar in both techniques (P = 0.52) and edge sharpness was significantly (P <0.0001) higher in FB-TRA compared to BH-MRA. BH-MRA provided overall diagnostic accuracy of 82%, and FB-TRA of 87%, with no statistical difference between the two sequences (P = 0.77). Vessel diameter measurements showed excellent agreement between the two techniques (r = 0.98, P <0.05), with no bias (0.0mm, P = 0.71), and clinically acceptable limits of agreement (-2.7 to +2.8mm). Inter and intra observer reproducibility showed good agreement of vessel diameters (r>0.988, P<0.0001), with negligible biases (between -0.2 and +0.1mm) and small limits of agreement (between -2.4 and +2.5mm). Conclusions: We have described a FB-TRA technique that is shown to enable accurate diagnosis and vessel measures compared to conventional BH-MRA. This simplifies the MRA technique and will enable angiography to be performed in children and adults whom find breath-holding difficult. © 2015 Steeden et al.; licensee BioMed Central. Source


O'Connor M.J.,Childrens Hospital of Philadelphia | Ravishankar C.,Childrens Hospital of Philadelphia | Ballweg J.A.,Childrens Hospital of Philadelphia | Gillespie M.J.,Childrens Hospital of Philadelphia | And 3 more authors.
Journal of Thoracic and Cardiovascular Surgery | Year: 2011

Objective: To determine the incidence, risk factors, and outcomes after early, unplanned intervention on systemic-to-pulmonary artery shunts in neonates. Methods: We retrospectively studied all neonates undergoing systemic-to-pulmonary artery shunt placement at The Children's Hospital of Philadelphia between September 1, 2002, and May 1, 2005. Patients requiring transcatheter or surgical systemic-to-pulmonary artery shunt intervention before discharge were compared with those not undergoing shunt intervention. Results: A total of 206 patients underwent shunt placement. Diagnoses included hypoplastic left heart syndrome (62.1%), pulmonary atresia (15%), tricuspid atresia (4.9%), tetralogy of Fallot (2.4%), and other lesions with obstruction to systemic (10.7%) or pulmonary blood flow (4.9%). Twenty-one interventions occurred in 20 patients (9.7%). Risk factors for intervention included heterotaxy syndrome (P = .04), congenital abnormality (P = .04), and a trend toward lower birthweight. In patients with a modified Blalock-Taussig shunt, similar risk factors were identified and the incidence of intervention decreased with increasing shunt size. In-hospital mortality was 30% (6/20) for the cases and 8.1% (15/186) for the nonintervention group (P = .02). Long-term survival was significantly lower in patients requiring intervention (P = .002). This group also had a higher incidence of infections (P < .001) and extracorporeal membrane oxygenation (P < .001), and longer hospital stay (P = .001). Conclusions: In neonates undergoing systemic-to-pulmonary artery shunt placement, approximately 10% underwent shunt intervention before discharge. Some factors, such as low birthweight, shunt size, noncardiac congenital abnormalities, and heterotaxy syndrome, may help identify patients at risk. Patients undergoing intervention experienced increased morbidity and mortality. Copyright © 2011 by The American Association for Thoracic Surgery. Source


Steeden J.A.,University College London | Pandya B.,University College London | Tann O.,Cardiorespiratory Unit | Muthurangu V.,University College London | Muthurangu V.,Cardiorespiratory Unit
Journal of Cardiovascular Magnetic Resonance | Year: 2015

Background: Contrast enhanced magnetic resonance angiography (MRA) is generally performed during a long breath-hold (BH), limiting its utility in infants and small children. This study proposes a free-breathing (FB) time resolved MRA (TRA) technique for use in pediatric and adult congenital heart disease (CHD). Methods: A TRA sequence was developed by combining spiral trajectories with sensitivity encoding (SENSE, x4 kx-ky and x2 kz) and partial Fourier (75% in kz). As no temporal data sharing is used, an independent 3D data set was acquired every ∼1.3s, with acceptable spatial resolution (∼2.3x2.3x2.3mm). The technique was tested during FB over 50 consecutive volumes. Conventional BH-MRA and FB-TRA data was acquired in 45 adults and children with CHD. We calculated quantitative image quality for both sequences. Diagnostic accuracy was assessed in all patients from both sequences. Additionally, vessel measurements were made at the sinotubular junction (N = 43), proximal descending aorta (N = 43), descending aorta at the level of the diaphragm (N = 43), main pulmonary artery (N = 35), left pulmonary artery (N = 35) and the right pulmonary artery (N = 35). Intra and inter observer variability was assessed in a subset of 10 patients. Results: BH-MRA had significantly higher homogeneity in non-contrast enhancing tissue (coefficient of variance, P <0.0001), signal-to-noise ratio (P <0.0001), contrast-to-noise ratio (P <0.0001) and relative contrast (P = 0.02) compared to the FB-TRA images. However, homogeneity in the vessels was similar in both techniques (P = 0.52) and edge sharpness was significantly (P <0.0001) higher in FB-TRA compared to BH-MRA. BH-MRA provided overall diagnostic accuracy of 82%, and FB-TRA of 87%, with no statistical difference between the two sequences (P = 0.77). Vessel diameter measurements showed excellent agreement between the two techniques (r = 0.98, P <0.05), with no bias (0.0mm, P = 0.71), and clinically acceptable limits of agreement (-2.7 to +2.8mm). Inter and intra observer reproducibility showed good agreement of vessel diameters (r>0.988, P<0.0001), with negligible biases (between -0.2 and +0.1mm) and small limits of agreement (between -2.4 and +2.5mm). Conclusions: We have described a FB-TRA technique that is shown to enable accurate diagnosis and vessel measures compared to conventional BH-MRA. This simplifies the MRA technique and will enable angiography to be performed in children and adults whom find breath-holding difficult. © 2015 Steeden et al.; licensee BioMed Central. Source


Young C.,University College London | Young C.,Cardiorespiratory Unit | Taylor A.M.,University College London | Taylor A.M.,Cardiorespiratory Unit | Owens C.M.,University College London
European Radiology | Year: 2011

The significant challenges involved in imaging the heart in small children (<15 kg) have been addressed by, and partially resolved with improvement in temporal and spatial resolution secondary to the advent of new multi-detector CT technology. This has enabled both retrospective and prospective ECG-gated imaging in children even at high heart rates (over 100 bpm) without the need for beta blockers. Recent studies have highlighted that the radiation burden associated with cardiac CT can be reduced using prospective ECG-gating. Our experience shows that the resultant dose reduction can be optimised to a level equivalent to that of a non-gated study. This article reviews the different aspects of ECG-gating and the preferred technique for cardiac imaging in the young child (<15 kg). We summarize our evidenced based recommendations for readers, referencing recent articles and using our in house data, protocols and dose measurements discussing the various methods available for dose calculations and their inherent bias. © 2010 European Society of Radiology. Source

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