Interaction between clinicians and artificial intelligence to detect fetal atrioventricular septal defects on ultrasound: how can we optimize collaborative performance?

OBJECTIVES

Artificial intelligence (AI) has shown promise in improving the performance of fetal ultrasound screening in detecting congenital heart disease (CHD). The effect of giving AI advice to human operators has not been studied in this context. Giving additional information about AI model workings, such as confidence scores for AI predictions, may be a way of improving performance further. Our aims were to investigate whether AI advice improved overall diagnostic accuracy (using a single CHD lesion as an exemplar), and to see what, if any, additional information given to clinicians optimized the overall performance of the clinician-AI team.

METHODS

An AI model was trained to classify a single fetal CHD lesion (atrioventricular septal defect, AVSD), using a retrospective cohort of 121,130 cardiac four chamber images extracted from 173 ultrasound scan videos (98 with normal hearts, 75 with AVSD). A ResNet50 model architecture was used. Temperature scaling of model prediction probability was performed on a validation set, and gradient-weighted class activation maps (grad-CAMs) produced. Ten clinicians (two consultant fetal cardiologists, three trainees in pediatric cardiology, and five fetal cardiac sonographers) were recruited from a center of fetal cardiology to participate. Each participant was shown 2000 fetal four chamber images in a random order (1,000 normal and 1,000 AVSD). The dataset was comprised of 500 images, each shown in four conditions: 1) image alone without AI output; 2) image with binary AI classification; 3) image with AI model confidence; 4) image with gradient-weighted class activation map image overlays. The clinicians were asked to classify each image as normal or AVSD.

RESULTS

20,000 image classifications were recorded from 10 clinicians. The AI model alone achieved an accuracy of 0.798 (95% CI 0.760 - 0.832), sensitivity of 0.868 (95% CI 0.834 - 0.902) and specificity of 0.728 (95% CI 0.702 - 0.754, and the clinicians without AI achieved an accuracy of 0.844 (95% CI 0.834 - 0.854), sensitivity of 0.827 (95% CI 0.795 - 0.858) and specificity of 0.861 (95% CI 0.828 - 0.895). Showing a binary (normal or AVSD) AI model output resulted in significant improvement in accuracy to 0.865 (p <0.001). This effect was seen in both experienced and less experienced participants. Giving incorrect AI advice resulted in significant deterioration in overall accuracy from 0.761 to 0.693 (p <0.001), which was driven by an increase in both type I and type II error by the clinicians. This effect was worsened by showing model confidence (accuracy 0.649, p <0.001) or grad-CAM (accuracy 0.644, p <0.001).

CONCLUSIONS

AI has the potential to improve performance when used in collaboration with clinicians, even if the model performance does not reach expert level. Giving additional information about model workings such as model confidence and class activation map image overlays did not improve overall performance, and actually worsened performance for images where the AI model was incorrect. This article is protected by copyright. All rights reserved.

Measurement of the cardiac time intervals of the fetal ECG utilising a computerised algorithm: A retrospective observational study

Objective

Establish whether the reliable measurement of cardiac time intervals of the fetal ECG can be automated and to address whether this approach could be used to investigate large datasets.

Design

Retrospective observational study.

Setting

Teaching hospitals in London UK, Nottingham UK and New York USA.

Participants

Singleton pregnancies with no known fetal abnormality.

Methods

Archived fetal ECG's performed using the MonicaAN24 monitor. A single ECG (PQRST) complex was generated from 5000 signal-averaged beats and electrical cardiac time intervals measured in an automated way and manually.

Main Outcome measure

Validation of a newly developed algorithm to measure the cardiac time intervals of the fetal ECG.

Results

188/236 (79.7%) subjects with fECGs of suitable signal:noise ratio were included for analysis comparing manual with automated measurement. PR interval was measured in 173/188 (92%), QRS complex in 170/188 (90%) and QT interval in 123/188 (65.4%). PR interval was 107.6 (12.07) ms [mean(SD)] manual vs 109.11 (14.7) ms algorithm. QRS duration was 54.72(6.35) ms manual vs 58.34(5.73) ms algorithm. QT-interval was 268.93 (21.59) ms manual vs 261.63 (36.16) ms algorithm. QTc was 407.5(32.71) ms manual vs 396.4 (54.78) ms algorithm. The QRS-duration increased with gestational age in both manual and algorithm measurements.

Conclusion

Accurate measurement of fetal ECG cardiac time intervals can be automated with potential application to interpretation of larger datasets.

3D/4D spatiotemporal image correlation (STIC) fetal echocardiography provides incremental benefit over 2D fetal echocardiography in predicting postnatal surgical approach in double-outlet right ventricle

OBJECTIVE

To analyze the incremental benefit of 3D/4D spatiotemporal image correlation (STIC) fetal echocardiography over 2D fetal echocardiography with respect to the accuracy of identification of anatomic details crucial for surgical decision-making and in predicting surgical approach in fetuses with double-outlet right ventricle (DORV).

METHODS

This was a retrospective study of fetuses with DORV which had undergone both 2D echocardiography and 3D/4D STIC echocardiography and which underwent surgery postnatally in a tertiary pediatric cardiac center in Kerala between October 2015 and March 2019. All such cases with normal atrial arrangement, concordant atrioventricular connections and balanced ventricles were included. 2D and 3D/4D STIC fetal echocardiographic data were analyzed by two experienced observers blinded to the other dataset. Anatomic variables crucial for surgical decision-making, i.e. location and routability of the ventricular septal defect, relationship of the great arteries and presence of outflow obstruction, were compared between the two modalities with respect to agreement with postnatal echocardiography. The accuracy of prenatal prediction of the surgical pathway was compared between 2D and 3D/4D modalities with respect to the procedure undertaken.

RESULTS

Included in the study were 22 fetuses with DORV which had undergone both 2D and 3D/4D imaging as well as postnatal surgery. Accuracy of prenatal interpretation of all four anatomic variables was significantly higher using 3D/4D STIC than using 2D fetal echocardiography (19/22 (86.4%) vs 8/22 (36.4%), P < 0.001). Surgical procedures included single-stage repair in 14 (63.5%) patients and a multistage approach in eight (36.4%). Prenatal prediction of the surgical pathway was significantly more accurate on 3D/4D STIC than on 2D echocardiography (20/22 (90.9%) vs 12/22 (54.5%), P = 0.021). Prenatal predictive accuracy of single-stage biventricular repair was significantly better for 3D/4D STIC than for 2D echocardiography (14/14 (100%) vs 8/14 (57.1%), P = 0.04).

CONCLUSION

Addition of 3D/4D STIC to conventional 2D fetal echocardiography confers incremental benefit on the accuracy of identification of anatomic details crucial for surgical decision-making and the prediction of postnatal surgical approach in fetuses with DORV, thereby potentially aiding prenatal counseling. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Immersive visualisation of intracardiac blood flow in virtual reality on a patient with HLHS

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): NIHR i4i funded 3D Heart project Wellcome/EPSRC Centre for Medical Engineering [WT 203148/Z/16/Z]

onbehalf

3D Heart Project

Background/Introduction: Virtual Reality (VR) for surgical and interventional planning in the treatment of Congenital Heart Disease (CHD) is an emerging field that has the potential to improve planning. Particularly in very complex cases, VR permits enhanced visualisation and more intuitive interaction of volumetric images, compared to traditional flat-screen visualisation tools. Blood flow is severely affected by CHD and, thus, visualisation of blood flow allows direct observation of the cardiac maladaptions for surgical planning. However, blood flow is fundamentally 3D information, and viewing and interacting with it using conventional 2D displays is suboptimal. 

Purpose

To demonstrate feasibility of blood flow visualisation in VR using pressure and velocity obtained from a computational fluid dynamic (CFD) simulation of the right ventricle in a patient with hypoplastic left heart syndrome (HLHS) as a proof of concept.

Methods

 We extend an existing VR volume rendering application to include CFD rendering functionality using the Visualization Toolkit (VTK), an established visualisation library widely used in clinical software for visualising medical imaging data. Our prototype displays the mesh outline of the segmented heart, a slicing plane showing blood pressure on the plane within the heart, and streamlines of blood flow from a spherical source region. Existing user tools were extended to enable interactive positioning, rotation and scaling of the pressure plane and streamline origin, ensuring continuity between volume rendering and CFD interaction and, thus, ease of use. We evaluated if rendering and interaction times were low enough to ensure a comfortable, interactive VR experience. Our performance benchmark is a previous study showing VR is acceptable to clinical users when rendering speed is at least 90 fps.

Results

CFD simulations were successfully rendered, viewed and manipulated in VR, as shown in the Figure. Evaluating performance, we found that visualisation of the mesh and streamlines was at an acceptably high and stable frame rate, over 150fps. User interactions of moving, rotating or scaling the mesh or streamlines origin did not significantly reduce this frame rate. However, rendering the  pressure slicing plane reduced frame rate by an unacceptable degree, to less than 10fps.  

Conclusion

Visualisation of and interaction with CFD simulation data was successfully integrated into an existing VR application. This aids in surgery and intervention planning for defects heavily relying on blood flow simulation, and lays a foundation for a platform for clinicians to test interventions in VR. Pressure plane rendering performance will require significant optimisation, potentially addressed by updating the pressure plane data separately from the main, VR rendering.

Abstract Figure. An example render of CFD simulation

Automatic orientation cues for intuitive immersive interrogation of 3D echocardiographic images in virtual reality using deep learning

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): NIHR i4i funded 3D Heart Project Wellcome / EPSRC Centre for Medical Engineering (WT 203148/Z/16/Z)

onbehalf

3D Heart Project

Background/Introduction:

In echocardiography (echo), image orientation is determined by the position and direction of the transducer during examination, unlike cardiovascular imaging modalities such as CT or MRI. As a result, when echo images are first shown their display orientation has no external anatomical landmarks, thus the user has to identify anatomical landmarks in the regions of interest to understand the orientation. 

Purpose

To display an anatomical model of a standard heart, automatically aligned to an acquired patient’s 3D echo image - assisting image interpretation by quickly orienting the viewer. 

Methods

 

47 echo datasets from 13 pediatric patients with hypoplastic left heart syndrome (HLHS) were annotated by manually indicating the cardiac axes in both ES and ED volumes. We chose a view akin to the standard four chamber view in healthy hearts as the reference view, showing the AV valves, the right atrium, the left atrium and the hypoplastic ventricle. We then trained a deep convolutional neural network (CNN) to predict the rotation required for re-orientation to the reference view. Three data strategies were explored: 1) using 3D images to estimate orientation, 2) using three orthogonal slices only (2.5D approach) and 3) using the central slice only (2D approach). Three different algorithms were investigated: 1) an orientation classifier, 2) an orientation regressor with mean absolute angle error, and 3) an orientation regressor with geodesic loss. The data was split into training, validation and test sets with a 8:1:1 ratio. The training data was augmented by applying random rotations in the range [−10◦, +10◦] and updating labels accordingly. The model with smallest validation error was applied in tandem with the VR visualisation of the echo volumes. 

Results

Experimental results suggest that a 2.5D CNN classifying discrete integer angles performs best in re-orienting volumetric images to the reference view, with a mean absolute angle error on the test set of 9.0 deg (test set error ranges from 10.8 to 25.9 deg. for other algorithms). An HLHS volumetric data (left) is automatically aligned with the cardiac model (right) using our trained network when loaded in VR as shown in Figure 1. The volume and the model are both cropped at the referencing plane.

Conclusion

A deep learning network to align 3D echo images to a reference view was successfully trained and then integrated  into VR to reorient echo volumes to match a standard anatomical view. This work demonstrates the potential of combining artificial intelligence and VR in medical imaging, although further user study is expected to evaluate its clinical impact.

Caption for Abstract Picture

 The VR user interface informs the user of the 3D echo image orientation, automatically aligning it with an anatomical model, here showing the four chamber apical view.

Abstract Figure. Deep learning model integrated into VR

Impact of prospective measurement of outflow tracts in prediction of coarctation of the aorta

OBJECTIVES

Prenatal diagnosis of coarctation of the aorta (CoA) is associated with reduced mortality and morbidity, however, accurate prenatal prediction remains challenging. To date, studies have used retrospective measurements of the outflow tracts to evaluate their potential to predict CoA. Our primary objective was to evaluate prospectively acquired measurements of the outflow tracts in fetuses with prenatally suspected CoA. A secondary aim was to report the postnatal prevalence of bicuspid aortic valve in this cohort.

METHODS

Pregnancies with suspicion of isolated CoA and with a minimum of 6 months' postnatal follow-up available were identified from the cardiac database of a tertiary fetal cardiology center in the UK, between January 2002 and December 2017. Measurement of the aortic valve, pulmonary valve, distal transverse aortic arch (DTAA) and arterial duct (AD) diameters were undertaken routinely in fetuses with suspected CoA during the study period. Z-scores were computed using published reference ranges based on > 7000 fetuses from our own unit.

RESULTS

Of 149 pregnancies with prenatally suspected CoA included in the study, CoA was confirmed within 6 months after birth in 77/149 (51.7%) cases. DTAA diameter Z-score and the Z-score of second-trimester DTAA/AD diameter ratio were smaller in fetuses with postnatally confirmed CoA than those in false-positive cases (-2.8 vs -1.9; P = 0.039 and -3.13 vs -2.61; P = 0.005, respectively). Multiple regression analysis demonstrated that the Z-scores of DTAA and AD diameters were the only significant predictors of postnatal CoA (P = 0.001). Bicuspid aortic valve was identified in 30% of the false-positive cases.

CONCLUSIONS

Measurement of DTAA and AD diameter Z-scores can be used to ascertain risk for postnatal CoA in a selected cohort. The high incidence of bicuspid aortic valve in false-positive cases merits further study with respect to both etiology and longer-term significance. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

P1417 Acceptability of a virtual reality system for examination of congenital heart disease patients

Funding Acknowledgements

Work supported by the NIHR i4i funded 3D Heart project [II-LA-0716-20001]

Background/Introduction

Virtual Reality (VR) has recently gained great interest for examining 3D images from congenital heart disease (CHD) patients. Currently, 3D printed models of the heart may be used for particularly complex cases. These have been found to be intuitive and to positively impact clinical decision-making. Although positively received, such printed models must be segmented from the image data, generally only CT/MR may be used, the prints are static, and models do not allow for cropping / slicing or easy manipulation. Our VR system is designed to address these issues, as well as providing a simple interface compared to standard software. Building such a VR system, one with intuitive interaction which is clinically useful, requires studying user acceptance and requirements.

Purpose: We evaluate the usability of our VR system

can a prototype VR system be easily learned and used by clinicians unfamiliar with VR.

Method

We tested a VR system which can display 3D echo images and enables the user to interact with them, for instance by translating, rotating and cropping. Our system is tested on a transoesophageal echocardiogram from a patient with aortic valve disease. 13 clinicians evaluated the system including 5 imaging cardiologists, 5 physiologists, 2 surgeons and an interventionist, with their clinical experience ranging from trainee to more than 5 years’ of experience. None had used VR regularly in the past. After a brief training session, they were asked to place three anatomical landmarks and identify a particular cardiac view. They then completed a questionnaire on system ease of learning and image manipulation.

Results: Results are shown in the figure below. Learning to use the system was perceived as easy for all but one participant, who rated it as ‘Somewhat difficult’. However, once trained, all users found the system easy to use. Participants found the interaction, where objects in the scene are picked up using the controller and then track the controller’s motion in a 1:1 way, to be particularly easy to learn and use.

Conclusion

Our VR system was accepted by the vast majority of clinicians, both for ease of learning and use. Intuitiveness and the ability to interact with images in a natural way were highlighted as most useful - suggesting that such a system could become accepted for routine clinical use in the future.

Abstract P1417 Figure. VR system evaluation participant feedbac

P1730 Multimodality assessment of complex ventricular septal defect

Conclusions

The key issue in this case is which of the muscular structures positioned at the ventricular apex is considered to be the true ventricular septum as this determines whether on not there is straddle of the tricuspid valve. In addition the complex and multiple nature of the chordal attachments below the valve made accessing and closing the defect not feasible.

Even in the present era with wide availability of advanced, multimodality imaging techniques demonstrating anatomy can still prove challenging in planning surgical repair, especially within the setting of complex congenital heart disease. Many aspects of such cases still only become apparent at the time of surgery and this remains a key issue when counselling parents.

Abstract P1730 Figure.

P801 A virtual reality tool for measurement of 3D echocardiographic images

Funding Acknowledgements

Work supported by the NIHR i4i funded 3D Heart project [II-LA-0716-20001]

Background/Introduction

Cardiac measurements are clinically important and are invariably required in any clinical imaging software. The advent of Virtual Reality (VR) imaging systems is introducing intuitive and natural ways of visualising and interrogating echo images in a 3D environment. The 3D nature of the VR experience requires purpose-designed measurement tools, which may benefit from better depth perception and easier localisation of 3D landmarks.

Purpose

Comparison of the accuracy of our VR 3D linear measurement system to commercial clinical imaging software, using both multi-plane reformatting (MPR) and volume rendered views.

Method

Each virtual reality measurement was made by selecting two points in 3D, directly in the volume rendering. The participants could edit the measurements until satisfied with their accuracy. 5 expert clinicians carried out 26 measurements each - 6 measurements on a calibration phantom, and 5 anatomically meaningful measurements (for example: aortic valve, left atrium, left ventricle) on 4 datasets. The same measurements were made by all participants using our VR system (volume rendering), Philips" QLAB (MPR) and Tomtec (volume rendering). The frame number and view (for example: long axis) were consistent for each measurement across the 3 packages used.

Results

Preliminary results are shown in the figure below. MPR measurements made on Philips’ QLAB are used as a reference, as this is the most commonly used software for this purpose at our institution. We compare measurements made in Tomtec and VR, both using volume rendering, using Bland-Altman plots. Each measurement data point is the mean of all participants measurements for each dataset/measurement combination. The mean of the measurement differences for the VR system is closer to zero, compared to Tomtec. However, the variation of these differences is larger for the VR system than for Tomtec.

Conclusion

Our preliminary results suggest that the accuracy of line measurements made using volume rendering within a VR system is comparable to measurements made using approved software packages for volume rendering displayed on a 2D screen. This shows promise for more complex interrogation methods.

Abstract P801 Figure. Comparison of Tomtec and VR with QLAB

P1566 Evaluation of haptic feedback for interaction with volumetric image data in virtual reality

Funding Acknowledgements

Work supported by the NIHR i4i funded 3D Heart project [II-LA-0716-20001]

Background

3D printing is used for surgical planning of complex congenital heart disease (CHD) because it provides an intuitive 3D representation of the image data. However, the 3D print is static and it can be costly and time consuming to create. Virtual Reality (VR) is a cheaper alternative that is able to visualise volumetric images in 3D directly from the scanner, both statically (CT and MR) and dynamically (cardiac ultrasound). However, VR visualisation is not as tangible as a 3D print - this is because it lacks the haptic feedback which would make the interactions feel more natural.

Purpose

Evaluate if adding haptic feedback (vibration) to the visualisation of volume image data in VR improves measurement accuracy and user experience.

Method

We evaluated the effect of vibration haptic feedback in our VR system using a synthetic cylinder volume dataset. The cylinder was displayed in two conditions: (1) with no haptic feedback, and (2) with haptic feedback. Ten non-clinical participants volunteered in the evaluation. They were blinded to these two test conditions. The participants were asked to measure the cylinder’s diameter horizontally and vertically, and its length, in each test condition. The measurement results were compared to the ground truth to assess the measurement accuracy. Each participant also completed a questionnaire comparing their experience of the two test conditions during the experiment.

Results

The results show a marginal improvement of measurement accuracy with haptic feedback, compared to no haptics (see Figure a). However, this improvement was not statistically significant. The haptic feedback did improve the participants’ confidence about their performance and increased the ease of use in VR, hence, they preferred the haptics condition to the no haptics condition (see Figure b). Moreover, although 70% of the participants reported relying on the visual cue more than on the haptic cue, 90% found that the haptic cue was helpful for deciding where to place the measurement point. Also, 88.9% of the participants felt more immersed in the VR scene with haptic feedback.

Conclusion

Our evaluation suggests that although haptic feedback may only marginally improve measurement accuracy, participants nevertheless preferred it because it improved confidence in their performance, increased ease of use, and facilitated a more immersive user experience.

Abstract P1566 Figure.

Myocardial deformation in fetuses with coarctation of the aorta: a case-control study

OBJECTIVE

To study myocardial deformation by speckle tracking echocardiography in fetuses with coarctation of the aorta (CoA) compared with gestational age-matched normal controls.

METHODS

This was a retrospective study of 12 fetuses with postnatally confirmed CoA and 12 gestational age-matched controls seen at a tertiary fetal cardiology unit between January 2013 and July 2014. Two-dimensional speckle tracking in standard grayscale four-chamber view of the fetal heart was performed to assess left and right myocardial deformation. Global longitudinal strain, strain rate and velocities, and regional longitudinal strain were analyzed and compared with controls.

RESULTS

Median gestational age at echocardiography was 25 + 4 weeks. Fetuses with CoA presented with a narrower, but not shorter, left ventricle when compared with controls (mitral valve diastolic diameter, 5.90 vs 8.50 mm; P = 0.002; left ventricular diastolic length, 16.50 vs 18.50 mm; P = 0.05). Global longitudinal systolic strain (P = 0.004), systolic strain rate (P = 0.01) and diastolic strain rate (P = 0.004) of the left ventricle were significantly lower in fetuses with CoA compared with controls. Similar findings were observed for longitudinal systolic (P = 0.03) and diastolic (P = 0.01) velocities of the left ventricle. Right ventricular parameters were not different between groups.

CONCLUSIONS

Fetuses with CoA have lower left ventricular longitudinal systolic strain, systolic strain rate and diastolic strain rate when compared with gestational age-matched control fetuses. These differences in deformation might explain, at least in part, the cardiac asymmetry observed in fetuses with CoA. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

The measurement properties and performance characteristics among older people of TURN180, a test of dynamic postural stability

Objectives: To establish the measurement properties of TURN180, a test of dynamic postural stability.

Design: One physiotherapist conducted three trials of TURN180, one of which was also observed by a second therapist.

Setting: A day unit for elderly people accepting both inpatients and outpatients.

Subjects: Sixty-six people (mean age 82.45 years), only six (9.1%) of whom could walk without using a walking aid.

Main measurement: The number of steps that a person takes to step around 180 degrees. A step is defined as any attempt on the subject's part to take a step, successful or not.

Results: Repeatability is good, intraclass correlation coefficient = 0.828; the minimal detectable change revealed that in order to be considered a real improvement the number of steps the person takes to complete the postintervention TURN180 must be 28–29% fewer than the preintervention count. As long as the protocol is followed carefully, between-observer agreement is good, with differences between two observers rarely exceeding one step. People who had fallen in the previous year took statistically significantly more steps than those who had not done so to complete TURN180. Requesting written as well as oral consent seems to reduce the likelihood of an elderly patient agreeing to participate in a study.

Conclusion: TURN180 yields repeatable (retest reliable) and valid data about a person's dynamic postural stability, especially the minimal detectable change which allows clinicians to judge whether any change in their patient's performance is real.

Use of complementary therapies in a sexual health clinic setting

This prospective cohort study examined the health-seeking behaviour of patients diagnosed with genital warts and vulvodynia who presented to Manly Sexual Health Service from March to June 2000. A self-administered questionnaire was used to assess patients' perceptions of their condition and their use of complementary therapies. Thirty-seven patients with genital warts and 26 patients with vulvodynia participated in the study. The use of at least one complementary health product or method was reported by 59% of patients with genital warts and 96% of vulvodynia patients ( P < 0.001). Having received conflicting information and being worried about the condition was significantly associated with visits to complementary health providers. Acknowledgement of this search for complementary therapies and open discussion can help patients make informed decisions and to avoid drug interactions, and should ultimately lead to better patient care.

A novel methodology for personalized simulations of ventricular hemodynamics from noninvasive imaging data

Current state-of-the-art imaging techniques can provide quantitative information to characterize ventricular function within the limits of the spatiotemporal resolution achievable in a realistic acquisition time. These imaging data can be used to personalize computer models, which in turn can help treatment planning by quantifying biomarkers that cannot be directly imaged, such as flow energy, shear stress and pressure gradients. To date, computer models have typically relied on invasive pressure measurements to be made patient-specific. When these data are not available, the scope and validity of the models are limited. To address this problem, we propose a new methodology for modeling patient-specific hemodynamics based exclusively on noninvasive velocity and anatomical data from 3D+t echocardiography or Magnetic Resonance Imaging (MRI). Numerical simulations of the cardiac cycle are driven by the image-derived velocities prescribed at the model boundaries using a penalty method that recovers a physical solution by minimizing the energy imparted to the system. This numerical approach circumvents the mathematical challenges due to the poor conditioning that arises from the imposition of boundary conditions on velocity only. We demonstrate that through this technique we are able to reconstruct given flow fields using Dirichlet only conditions. We also perform a sensitivity analysis to investigate the accuracy of this approach for different images with varying spatiotemporal resolution. Finally, we examine the influence of noise on the computed result, showing robustness to unbiased noise with an average error in the simulated velocity approximately 7% for a typical voxel size of 2mm(3) and temporal resolution of 30ms. The methodology is eventually applied to a patient case to highlight the potential for a direct clinical translation.

Prenatal diagnosis of left ventricular diverticulum and coarctation of the aorta

Congenital left ventricular diverticulum (LVD) is a rare abnormality of the myocardium which has been detected previously in the fetus. Lesions have been reported from as early as 12 weeks' gestation but are more commonly detected in the mid-second trimester. Fetal presentation of LVD ranges from an abnormal four-chamber view of the heart, arrhythmia or isolated pericardial effusion to fetal hydrops with associated heart failure. Here, we describe the prenatal diagnosis of an infant with LVD originating from the left ventricular outflow tract associated with coarctation of the aorta. The diagnosis was confirmed postnatally by two-dimensional echocardiography and cardiac magnetic resonance imaging. We hypothesize that the lesion compromised antegrade flow into the transverse aortic arch, which may have contributed to underdevelopment of the aortic arch and subsequently the development of coarctation of the aorta. This is a unique case of LVD and coarctation of the aorta.

Accuracy of the transpulmonary ultrasound dilution method for detection of small anatomic shunts

The purpose of this study was to investigate the qualitative and quantitative accuracy of transpulmonary ultrasound dilution (UD) (COstatus™, Transonic Systems) for the detection of small anatomic shunts. It was a prospective, observational study in a multi-disciplinary pediatric intensive care unit. Seventy-three critically ill children (67 post cardiac surgery), with a median (IQR) age of 10 (3-50.3) months and a median (IQR) weight of 8 (3.43-13) kg were enrolled. Ultrasound dilution (UD) measurements were performed on patients within 1 h of undergoing two-dimensional echocardiography, which was used as the comparator technique. Shunt was diagnosed by characteristic changes on the UD curve shape, and was considered "test-positive" only if two or more measurements suggested the presence of the shunt. The UD technology also provided an estimate of pulmonary to systemic blood flow ratio (Qp:Qs). 12/73 (16.4 %) patients had a shunt identified by both UD and echocardiography. The overall accuracy (95 % CI) was 86.1 % (75.6-96.6 %), with a sensitivity of 85.7 % (57.2-98.2 %) and specificity of 86.4 % (75.0-94.0 %). The estimated Qp:Qs ranged from 0.7 to 1.4, which was consistent qualitatively with the echocardiographic findings on color flow doppler. Shunt was detected by UD alone in eight children; six of these had clinical conditions known to compromise dilution curve analysis (valve regurgitation, asymmetric pulmonary blood flow). Shunt was detected by echocardiography alone in two children; in both cases the shunt was tiny. UD is an accurate method for the detection of small anatomical shunts, both qualitatively and quantitatively.

Towards a fast and efficient approach for modelling the patient-specific ventricular haemodynamics

Computer modelling of the heart has emerged over the past decade as a powerful technique to explore the cardiovascular pathophysiology and inform clinical diagnosis. The current state-of-the-art in biophysical modelling requires a wealth of, potentially invasive, clinical data for the parametrisation and validation of the models, a process that is still too long and complex to be compatible with the clinical decision-making time. Therefore, there remains a need for models that can be quickly customised to reconstruct physical processes difficult to measure directly in patients. In this paper, we propose a less resource-intensive approach to modelling, whereby computational fluid-dynamics (CFD) models are constrained exclusively by boundary motion derived from imaging data through a validated wall tracking algorithm. These models are generated and parametrised based solely on ultrasound data, whose acquisition is fast, inexpensive and routine in all patients. To maximise the time and computational efficiency, a semi-automated pipeline is embedded in an image processing workflow to personalise the models. Applying this approach to two patient cases, we demonstrate this tool can be directly used in the clinic to interpret and complement the available clinical data by providing a quantitative indication of clinical markers that cannot be easily derived from imaging, such as pressure gradients and the flow energy.

Outcome and requirement for surgical repair following prenatal diagnosis of ventricular septal defect

OBJECTIVE

To document outcome following prenatal diagnosis of ventricular septal defects (VSDs), particularly associated anomalies and the requirement for surgical closure of the defect.

METHODS

All cases of prenatal diagnosis of a VSD made by fetal cardiologists at a tertiary fetal medicine referral center in the period January 2002 to December 2011 were extracted from our database. Data regarding fetal cardiac diagnosis, extracardiac anomalies, nuchal translucency thickness and karyotype were noted.

RESULTS

A total of 171 cases fulfilled our selection criteria. Of these, 69% were diagnosed with a perimembranous VSD and 31% with a muscular defect. The median gestational age at diagnosis was 21 + 6 (range, 12 + 0 to 37 + 3) weeks. Owing to severe extracardiac or genetic conditions, pregnancy resulted in intrauterine death or termination in 49% cases, and postnatal death occurred in 9% of cases. Seventy-two babies were liveborn, and were regarded as potential surgical candidates if hemodynamics suggested that surgery was indicated. Surgical closure of the VSD proved necessary in 50% of the patients with a perimembranous VSD and 13% of those with a muscular VSD. All patients operated on survived surgical repair. No karyotypic abnormalities were identified in fetuses with VSDs that had normal first-trimester screening and no other sonographic abnormalities.

CONCLUSIONS

A high proportion of VSDs diagnosed during fetal life (29%) require postnatal surgical intervention. The assessment of hemodynamic significance from fetal echocardiography is imperfect. The presence of extracardiac abnormalities or abnormal results on first-trimester screening has a major impact on the incidence of karyotypic abnormalities in affected fetuses. This should inform discussions with parents about invasive testing.

Atopy phenotypes in the Childhood Asthma Prevention Study (CAPS) cohort and the relationship with allergic disease: clinical mechanisms in allergic disease

BACKGROUND

Atopy in early life is heterogeneous in timing of onset, remission and persistence and in the nature of specific sensitization to allergens. However, this heterogeneity is not well characterized.

OBJECTIVE

Our aim was to define longitudinal phenotypes of atopy between ages 1.5 and 8 years, and to assess the relationship of the atopy phenotypes to the risk of asthma, eczema and rhinitis at 8 years of age.

METHODS

We used latent class analysis (LCA) to define atopy phenotypes using data from skin prick tests that were performed at 1.5, 3, 5 and 8 years in participants in the Childhood Asthma Prevention Study (CAPS).

RESULTS

Four phenotypes were defined: late mixed inhalant sensitization; mixed food and inhalant sensitization; house dust mite (HDM) monosensitized; and no atopy. All three atopic phenotypes were associated with asthma, eczema and rhinitis, but the strongest association, particularly for asthma, was with the mixed food and inhalant sensitization phenotype.

CONCLUSION & CLINICAL RELEVANCE

We have used a LCA model to define atopy phenotypes empirically. The finding of a strong association between the mixed food and inhalant sensitization class and the presence of asthma and poor asthma control at age 8 years implies that food sensitization in early life may be of greater significance for subsequent risk of asthma than previously thought.

Three-dimensional fetal echocardiography for prediction of postnatal surgical approach in double outlet right ventricle: a pilot study

OBJECTIVES

To examine the feasibility of reconstructing three-dimensional (3D) echocardiographic views in fetuses with double outlet right ventricle, which might enhance prognostication with respect to the postnatal surgical approach.

METHODS

This was a retrospective blinded observational study. Our database was reviewed from January 2007 to June 2011 to identify fetuses with usual atrial arrangement, concordant atrioventricular connections, double outlet right ventricle and relatively balanced left and right ventricular size. Six fetuses, in which there was an intention to treat, were included.

RESULTS

In all six cases, we identified important features, including location of the ventricular septal defect and its relation to the atrioventricular valves and great arteries. The postnatal surgical approach was predicted accurately in each case.

CONCLUSION

In this group of fetuses with double outlet right ventricle, detailed evaluation by 3D fetal echocardiography enhanced visualization of the anatomy, leading to accurate prediction of the type of surgical repair. Prospective validation in a large cohort of fetuses is warranted.

Body mass index, sexual difficulties and sexual satisfaction among people in regular heterosexual relationships: a population-based study

BACKGROUND/AIMS

The aims of this study were to clarify the relationship between body mass index (BMI) and sexual difficulties and to investigate if BMI influenced sexual satisfaction, over and above the effects of sexual difficulties.

METHODS

Cross-sectional analyses of a nationally representative computer-assisted telephone interview. Eight thousand, six hundred and fifty-six respondents were recruited by random digit dialling in 2004-2005. Only those in a sexually active, heterosexual relationship were included in the current analyses.

RESULTS

After adjustments for demographic factors, both overweight and obese male and female participants were more likely to report worrying during sex about whether their body was unattractive. Among women, associations were also found between higher BMI and lack of interest in sex. No other significant associations between BMI and sexual difficulties were evident. There was an association between BMI and extreme physical pleasure for women but not men over and above the effects of sexual difficulties, with obese women being more likely than normal weight women to report extreme physical pleasure. No associations were found for either men or women between BMI and whether or not they reported extreme emotional or sexual satisfaction with their relationship.

CONCLUSIONS

With the exception of body image difficulties, there is little association between BMI and self-reported sexual difficulties. Furthermore, extreme sexual and emotional satisfaction appeared to be associated with the presence or absence of sexual difficulties and not overly influenced by BMI. Overall, clinicians and patients should be aware that being overweight is not necessarily detrimental to sexual functioning.

Does increased sunlight exposure work as a strategy to improve vitamin D status in the elderly: a cluster randomised controlled trial

SUMMARY

Sunlight exposure by improving vitamin D status could be a simple public health strategy in reducing falls among frail elder people. In a randomised controlled trial, adherence to sunlight exposure was low (median adherence, 26%) and no effect of increased UV exposure on falls risk was observed (incidence rate ratio (IRR) 1.06, P = 0.73).

INTRODUCTION

This study aimed to determine whether increased sunlight exposure was effective to improve vitamin D status and reduce falls in the elderly.

METHODS

In a cluster randomised controlled trial (NCT00322166 at ClinicalTrials.gov), 602 residents aged 70 or more (mean age, 86.4 years; 71% female) were recruited from 51 aged care facilities in Northern Sydney, Australia. Participants were randomised by facility to receive either increased sunlight exposure (additional 30-40 min/day in the early morning) with (UV+) or without (UV) calcium supplementation (600 mg/day) or neither (control) for a year. The co-primary endpoints were change in serum 25 hydroxy vitamin D (25OHD) and falls incidence after 12 months.

RESULTS

Adherence to sunlight exposure was low (median adherence, 26%; IQR, 7%-45%). Serum 25OHD levels were low at baseline (median, 32.9 nmol/L) and increased only slightly depending on the number of sunlight sessions attended over 12 months (P = 0.04). During the study, 327 falls occurred in 111 (54%) subjects in the control group, 326 falls in 111 (58%) subjects in the UV only group and 335 falls in 108 (52%) subjects in the UV+ group. By intention-to-treat analysis, there was no significant effect of increased UV exposure on falls risk (IRR, 1.06; 95% CI, 0.76-1.48; P = 0.73). However, in 66 participants who attended ≥130 sessions per year (adherence, ≥50% of 260 sessions-five per week), falls were significantly reduced (IRR, 0.52; 95% CI, 0.31-0.88; P = 0.01) compared with the control group.

CONCLUSIONS

Increased sunlight exposure did not reduce vitamin D deficiency or falls risk in frail older people. This public health strategy was not effective most likely due to poor adherence to the intervention.

Interobserver agreement in detailed prenatal diagnosis of congenital heart disease by telemedicine using four-dimensional ultrasound with spatiotemporal image correlation

OBJECTIVE

To evaluate the clinical accuracy of four-dimensional (4D) echocardiography in the detailed prenatal diagnosis of congenital heart disease (CHD) in a telemedicine setting.

METHODS

Ten second-trimester spatiotemporal image correlation (STIC) volumes were sent to three observers in different tertiary care centers with expertise in 4D echocardiography. The 10 volumes were selected based on the type of diagnosis to cover a wide spectrum of CHD anomalies, and also included one normal fetal heart. Observers were asked to provide the diagnosis, the postprocessing modalities used and the time spent on examination, and to give a rating of the confidence for the diagnosis on a 5-point Likert scale. They were free to consult other colleagues, including pediatric cardiologists, but were blinded to the prenatal diagnosis and the neonatal outcome. A diagnostic scoring system was used to evaluate different aspects of the heart defects. The results were compared with neonatal echocardiography or postmortem findings ('gold standard').

RESULTS

In two cases all observers correctly diagnosed all details of the volume datasets. The observer with the best performance reached perfect agreement in six cases and nearly perfect agreement in three. The volumes were most frequently studied by sectional planes and were analyzed in a median time of 11.0 (range, 2.5-30.0) min. The median confidence score was 4.0 (range, 1.0-5.0).

CONCLUSIONS

In a telemedicine setting using STIC volumes, fetal cardiac anomalies can be diagnosed correctly by an expert. However, details required for adequate counseling and planning of postnatal care may be missed. STIC by telemedicine is a promising modality, although not accurate enough for exclusive use in clinical decision making regarding treatment, prognosis or termination of pregnancy.

Oral bisphosphonates are associated with reduced mortality in frail older people: a prospective five-year study

In a study of 2005 institutionalized older people, use of oral bisphosphonates was associated with a 27% reduction in risk of death compared to non-users after adjusting for potential confounders.

INTRODUCTION

This study investigated whether reductions in mortality reported in a trial of intravenous zoledronate after hip fracture could be seen in older people taking oral bisphosphonates.

METHODS

Two thousand and five institutionalized older people (mean age 85.7 years) were assessed at baseline and followed up for hip fracture and death for at least 5 years. Cox proportional hazards regression was used to estimate effects of bisphosphonates on risk of death.

RESULTS

At baseline, 78 subjects were taking oral bisphosphonates. Over 5 years of follow-up, 1,596 participants (80%) died. Use of bisphosphonates was associated with a 27% reduction in risk of death compared to non-users after adjusting for age, gender, type of institution, immobility, number of medications, weight, cognitive function, co-morbidities, and hip fracture incidence during the follow-up period (hazard ratio 0.73; 95% CI, 0.56 to 0.94; P = 0.02).

CONCLUSION

Oral bisphosphonates are associated with a reduction in the risk of death in the elderly. The mechanism of effect requires further investigation.

Significant shift in median guinea pig infectious dose shown by an outbreak-associated Listeria monocytogenes epidemic clone strain and a strain carrying a premature stop codon mutation in inlA

Listeria monocytogenes contains (i) epidemic clone (EC) strains, which have been linked to the majority of listeriosis outbreaks worldwide and are overrepresented among sporadic cases in the United States, and (ii) strains commonly isolated from ready-to-eat foods that carry a mutation leading to a premature stop codon (PMSC) in inlA, which encodes the key virulence factor internalin A (InlA). Internalin A binds certain isoforms of the cellular receptor E-cadherin to facilitate crossing the intestinal barrier during the initial stages of an L. monocytogenes infection. Juvenile guinea pigs, which express the human isoform of E-cadherin that binds InlA, were intragastrically challenged with a range of doses of (i) an EC strain associated with a listeriosis outbreak or (ii) a strain carrying a PMSC mutation in inlA. Recovery of L. monocytogenes from tissues (i.e., liver, spleen, mesenteric lymph nodes, and ileum) was used to develop strain-specific dose-response curves on the basis of individual and combined organ data. Modeling of individual and combined organ data revealed an approximate 1.2 to 1.3 log(10) increase in the median infectious dose for the strain carrying a PMSC in inlA relative to that for the EC strain. Inclusion of the strain parameter significantly improved the goodness of fit for individual and combined organ models, indicating a significant shift in median infectious dose for guinea pigs challenged with an inlA PMSC strain compared to that for guinea pigs challenged with an EC strain. Results from this work provide evidence that the L. monocytogenes dose-response relationship is strain specific and will provide critical data for enhancement of current risk assessments and development of future risk assessments.

Infant and early childhood dietary predictors of overweight at age 8 years in the CAPS population

BACKGROUND/OBJECTIVES

Programs to address obesity are a high priority for public policy especially for young children. Research into dietary determinants of obesity is challenging but important for rational planning of interventions to prevent obesity, given that both diet and energy expenditure influence weight status. We investigated whether early life dietary factors were predictive of weight status at 8 years in a cohort of Australian children.

SUBJECTS/METHODS

We used data from the Childhood Asthma Prevention Study-a birth cohort at high risk of asthma. Dietary data (3-day weighed food records) were collected at 18 months and height, weight and waist circumference were collected at 8 years. We assessed the relationship between dietary predictor variables and measures of adiposity using linear regression.

RESULTS

Intakes of protein, meat and fruit at age 18 months were positively associated with measures of adiposity at age 8 years, namely, body mass index and/or waist circumference. We also showed a significant negative relationship between these measures of adiposity at 8 years and intake at 18 months of dairy foods as a percent of total energy, and intake of energy dense cereal-based foods such as cookies and crackers.

CONCLUSIONS

This birth cohort study with rigorous design, measures and analyses, has shown a number of associations between early dietary intake and subsequent adiposity that contribute to the growing evidence base in this important field.

Resurfacing registers concern

We review the history and literature of hip resurfacing arthroplasty. Resurfacing and the science behind it continues to evolve. Recent results, particularly from the national arthroplasty registers, have spread disquiet among both surgeons and patients. A hip resurfacing arthroplasty is not a total hip replacement, but should perhaps be seen as a means of delaying it. The time when hip resurfacing is offered to a patient may be different from that for a total hip replacement. The same logic can apply to the timing of revision surgery. Consequently, the comparison of resurfacing with total hip replacement may be a false one. Nevertheless, the need for innovative solutions for young arthroplasty patients is clear. Total hip replacement can be usefully delayed in many of these patients by the use of hip resurfacing arthroplasty.

Condom use in multi-partnered males: importance of HIV and hepatitis B status

The objective of the research was to determine the demographic, sexual and social risk factors associated with condom use in 7,089 multi-partnered men attending the Sydney Sexual Health Centre. A review of computerized medical records from 1991 to 1999 was carried out. Males with two or more partners in the last three months were divided into three condom use groups: consistent, sometimes and never. Men reporting sex with men (MSM) were more likely to use condoms than men having sex with only women (p=0.001). HIV positive men were more likely to use condoms consistently than those who were negative (p=0.001). In HIV negative non-hepatitis-B carriers, factors independently associated with inconsistent condom use included alcohol consumption, intravenous drug use (odds ratio (OR) 0.6 (95% confidence interval (CI) 0.47-0.77)) and being married (OR 0.2 (95% CI 0.21-0.31)). Factors associated with consistent condom use were MSM (OR 1.8 (95% CI 1.26-2.49)) and having three or more partners in the last 3 months (OR 2.4 (95% CI 2.023-2.83)). In the 508 hepatitis B carriers, consistent condom users were less likely to be married or intravenous drug users (OR 0.4 (95% CI 0.23-0.85)). In the 200 HIV antibody positive men, those with three or more partners were less likely to be consistent condom users than those with two (OR 0.3 (95% CI 0.11-0.82)). The conclusions are that a small number of HIV positive men report unsafe sex with multiple partners. Health promotion activities should be directed at this group.

Fetal ventricular tachycardia secondary to long QT syndrome treated with maternal intravenous magnesium: case report and review of the literature

Ventricular tachycardia is a very rare fetal arrhythmia accounting for fewer than 2% of fetal tachycardias. We describe a fetus presenting at 30 weeks' gestation with ventricular tachycardia at a rate of 220 beats per min and fetal hydrops. The tachycardia was unresponsive to flecainide but was controlled within 12 h by an intravenous infusion of magnesium to the mother. Despite rapid control of the arrhythmia the fetus developed severe periventricular leukomalacia before birth for which a poor neurological prognosis was given. The baby was delivered preterm at 32 weeks' gestation and died on the sixth day after birth. Long QT syndrome was identified postnatally on the electrocardiogram, and was confirmed by genetic testing which showed a mutation in the KCNH2 gene (p.T613M).