Nee Scze Khoo

Background: Cardiac allograft vasculopathy (CAV) is the leading cause of late graft loss in children after pediatric heart transplantation (HTx). Coronary angiography, the reference standard for diagnosis, is invasive and carries a risk of complications. Noninvasive echocardiographic methods to reliably identify CAV in children have not yet been defined. Methods: This study assessed the utility of functional echocardiography (FE) in the diagnosis of CAV in children. We prospectively assessed all children (< 18 years old) post‐HTx during routine clinical surveillance between 2005 and 2020. For this study, we compared patients diagnosed with CAV (angiographic ISHLT criteria) with transplanted children without CAV, with FE at the time of diagnosis (d‐CAV) and 6–12 months before diagnosis (pre‐CAV), and evaluated clinical risk factors. Results: We identified 10 children with CAV and 11 matched controls (CON). Right ventricular longitudinal strain (RV LS) and strain rate (RV LSR) were reduced at d‐CAV (d‐CAV RV LS, 12.1% [9.2,16.1] vs. CON RV LS, 21.5% [18.2,25.7]; d‐CAV RV LSR, 0.75%/s [0.48, 0.98] vs. CON RV LSR, 1.35%/s [0.95,1.50], p < 0.01 for all) and pre‐CAV (pre‐CAV RV LS, 17.3% [10.8,20.2] vs. CON RV LS, 21.5% [18.2,25.7]; pre‐CAV RV LSR 0.95%/s [0.80,1.10] vs. CON RV LSR, 1.35%/s [0.95,1.50], p ≤ 0.05 for all). Patients with CAV were more likely to have class II donor‐specific antibodies ( p = 0.01). Conclusion: Right ventricle systolic strain parameters were reduced as early as 12 months prior to CAV diagnosis, while the left ventricle functional parameters remained preserved. FE of the right ventricle may be a useful noninvasive tool for early recognition of developing CAV in transplanted children.

Background: Echocardiography parameters of right ventricular (RV) dysfunction, fractional area change (RVFAC), and global longitudinal strain during the first interstage have been shown to be associated with death or transplantation in patients with HLHS. However, both parameters lack adequate discriminatory characteristics. This study sought to examine global post‐systolic contraction (PSC), a marker of myocardial inefficiency, as a predictor of death or transplantation (Tx) in patients with classic hypoplastic left heart syndrome (HLHS).Methods: We performed a post‐hoc analysis of 62 prospectively recruited patients with HLHS prior to the bidirectional cavopulmonary anastomosis (BCPA) surgery. We measured RV function parameters: RVFAC, global longitudinal strain, strain rate, mechanical dispersion index (MDI), and PSC. For each parameter, the receiver operating characteristic analysis determined the optimal cut‐offs for the primary endpoint of death/Tx, followed by a Kaplan‐Meier analysis. Parameters interobserver variability testing was performed.Results: Median follow‐up from pre‐BCPA echocardiogram was 7.4 years. HLHS with outcome of death/Tx (n = 14) had lower RVFAC, longitudinal strain and strain rate, and increased PSC when compared with survivors. PSC of >5% performed the best, with the greatest area under the curve 0.75, sensitivity 64% and specificity 83%, hazard ratio 5.54 (95% CI 1.63–18.66), for the primary endpoint of death/Tx. PSC and strain parameters had excellent reproducibility.Conclusion: Increased global post‐systolic contraction during the first interstage is associated with an outcome of death or transplantation in the medium term follow up of patients with HLHS. PSC has a greater specificity and reproducibility than global longitudinal strain and RV FAC. Investigation into its use in clinical practice as a predictor of outcome is warranted.

The double-orifice tricuspid valve (DOTV) is a rare lesion. We present a series of three patients encountered at the Stollery Children’s Hospital with a diagnosis of DOTV on 2D and/or 3D echocardiography. The patient’s medical records are reviewed for presentation history, investigative findings, and clinical course. We discuss the cases in the context of a complete review of all literature documenting cases of DOTV. In the majority of cases, the lesion is relatively benign, with little change in valve function over the short to medium term, and outcomes are determined largely by significant concomitant heart defects.

Three-dimensional ultrasound offers volumetric images and detailed anatomical data for medical diagnosis and treatment planning. It is a key tool in the medical field to obtain a comprehensive view of the body. Ordinary two-dimensional displays do not provide depth perception and are not suitable for representing volumetric data, necessitating the use of more sophisticated visualization methods. Virtual and augmented reality (AR) displays can be used to improve the visualization of medical images, allowing for more natural interaction with the environment. This study proposes custom software developed using the Unity3D platform to render high-resolution 3D echocardiography (3DE) on the Microsoft HoloLens 2, providing an immersive AR experience for medical professionals. This research focuses on three-dimensional echocardiography in children and uses a phantom heart model to mimic a pulsating heart. The volume rendering algorithm utilizes the ray-marching technique, enabling direct volume rendering of high-quality volumetric models. To maintain a satisfactory frame rate, a Holographic Remoting approach is employed to reduce latency and enhance network transmission speed, utilizing the resources of a personal computer (PC). The custom software developed offers an intuitive and interactive user interface that allows medical professionals to manipulate and explore 3DE images effectively. The interaction includes the ability to slice, modify the intensity range, and alter the voxel density. The experimental evaluations demonstrated that it is possible to produce high-quality real-time display with HoloLens 2 and a PC-based remote rendering system, allowing intuitive control and exploration of 3DE. Overall, this research highlights the potential of AR rendering offered through Microsoft HoloLens 2 to advance pediatric 3DE rendering for medical professionals to enhance their decision-making and understanding of medical datasets.

Anomalies of the tricuspid valve (TV) are associated with worsened prognosis in congenital heart disease (CHD). Here, we present a descriptive study examining changes in TV morphology in two CHD conditions—repaired tetralogy of Fallot (rTOF) and hypoplastic left heart syndrome (HLSH), using three-dimensional echocardiography. Full volume acquisitions of the TV and right ventricle (RV) were performed from an RV-focused apical view using ECG gating over 2–5 consecutive cardiac cycles using 3D echocardiography, from which TV annulus and leaflet parameters were quantified. A total of 40 rTOF patients (age 14 ± 9.8 years), 40 HLHS patients (age1.0 ± 1.5 years) and 80 age and gender matched controls were included. Among leaflet parameters, antero-posterior and posterior-septal TV coaptation heights were smaller in rTOF (p < 0.001) vs. control. Conversely, only the short-axis TV height was different in HLHS vs. controls (HLHS 1.6 ± 0.4 cm vs. control 1.4 ± 0.3 cm). TV leaflet parameters tended to be larger in HLHS, while leaflet coaptation distances were similar between groups. We demonstrate that 3D echocardiography for assessment of the TV is feasible in rTOF and HLHS patients and identifies unique differences in TV morphology. Future studies should clarify the clinical significance of TV morphology in these patient populations.

Right ventricular (RV) remodeling in hypoplastic left heart syndrome (HLHS) begins prenatally and continues through staged palliations. However, it is unclear if the most marked observed remodeling post-Norwood is secondary to cardiopulmonary bypass (CPB) exposure or if it is an adaptation intrinsic to the systemic RV. This study aims to determine the impact of CPB on RV remodeling in HLHS. Echocardiograms of HLHS survivors undergoing stage 1 Norwood (n = 26) or Hybrid (n = 20) were analyzed at pre- and post-stage 1, pre- and post-bidirectional cavo-pulmonary anastomosis (BCPA), and pre-Fontan. RV fractional area change (FAC), vector velocity imaging for longitudinal & derived circumferential deformation (global radial shortening (GRS) = peak radial displacement/end-diastolic diameter), and deformation ratio (longitudinal/ circumferential) were assessed. Both groups had similar age, clinical status and functional parameters pre-stage 1. No difference in RV size and sphericity at any stage between groups. RVFAC was normal (> 35%) throughout for both groups. Both Norwood and Hybrid patients had increased GRS (p = 0.0001) post-stage 1 and corresponding unchanged longitudinal strain, resulting in decreased deformation ratio (greater relative RV circumferential contraction), p = 0.0001. Deformation ratio remained decreased in both groups in subsequent stages. Irrespective of timing of the first CPB exposure, both Norwood and Hybrid patients underwent similar RV remodeling, with relative increase in circumferential to longitudinal contraction soon after stage 1 palliation. The observed RV remodeling in HLHS survivors were minimally impacted by CPB.

Post-natal maturation of the myocardium starts shortly after birth and could affect how clinicians should provide hemodynamic support during this transition. Our aim was to assess the impact of post-natal maturation on tolerance to tachycardia with altered loading condition in a piglet model. Methods: We report three series of experimentations. Six groups of landrace cross neonatal piglets (NP) (1–3 days) and young piglets (YP) (14–17 days) were assigned to tachycardia (NP, YP), tachycardia and hypervolemia (NPV, YPV) or tachycardia and increased afterload (NPA, YPA) groups (n = 7/group). Under anesthesia, a pressure catheter was placed in the left ventricle and pacing wire in the right atrium. NPV and YPV groups had 60 ml/kg of normal saline infused over 20 min. NPA and YPA had balloon sub-occlusion of the descending aorta. Heart rate was increased by 10 bpm increments to 300 bpm. Left ventricular output was measured by echocardiography. Results: NP maintained left ventricular output throughout the pacing protocol but it decreased in the YP (p < 0.001). With volume loading both NPV and YPV maintained their output with tachycardia. Although increased afterload resulted in reduced output during tachycardia in NPA (p = 0.005), there was no added impact on output in YPA. Interestingly, 4 of 7 NPV had significant desaturation at 300 bpm (baseline 99.7% vs. 300 bpm 87.9%, p = 0.04), associated with a right to left shunt through the patent foramen ovale which resolved immediately on cessation of pacing. Conclusions: Early post-natal maturation is associated with improved myocardial tolerance to increased afterload and poor tolerance of tachycardia, the latter of which may be alleviated by increasing intravascular volume. These data could translate into the development of better strategies to optimize cardiac output at these early development ages.