Shi-Joon Yoo’s research while affiliated with University of Toronto and other places

Introduction: Patients who underwent arterial switch operation (ASO) for d-transposition of the great arteries (TGA) are at increased risk for early myocardial ischemia. Stress perfusion cardiac MR (SPCMR) is used as a non-invasive tool for risk stratification but interpretation is often challenging. Hypothesis: There is significant interobserver variability in SPCMR image interpretation in patients with repaired TGA. Aims: 1. Determine incidence and severity of adverse effects of stress agents. 2. Evaluate incidence of positive SPCMR. 3. Assess agreement amongst reviewers in image interpretation. Methods: Patients with repaired TGA with SPCMR imaging from 2013 to 2024 were reviewed. Three patients with previous coronary intervention and one with severe chest pain after adenosine, unable to complete SPCMR, were excluded. 61 studies were performed in 56 patients. Images were independently reviewed by two investigators blinded to initial interpretation and clinical outcome. Perfusion defects were displayed on a circumferential polar plot using standard LV segmentation. Results: Median (IQR) age was 15 (11-17) years, weight 55 (36-68) kg, and BSA 1.6 (1.2-1.8) m2. Max heart rate was 110 (100-125) and systolic BP 127 (116-138). Eleven (20%) patients had cardiac symptoms, chest pain in 9 (16%), syncope in 1 (2%), pallor and distress in 1 (2%) infant. Adverse effects from SPCMR in 8/52 (15%) adenosine, 2/4 (50%) dobutamine, and 0/6 (0%) regadenoson were minor and resolved on stress completion. Six (10%) studies were initially interpreted as suspicious (n=5) or definitive (n=1) perfusion defect (Figure). No LGE was detected. Original interpretation did not match blinded reviews for 6 cases (Figure). Blinded reviewers agreed on 3 negative cases but interpretation differed in the other 3 cases (Figure). Conclusions: SPCMR is safe and feasible. Significant interobserver variability highlights the challenges in qualitative SPCMR interpretation for TGA. Quantitative perfusion may reduce interobserver variability. Larger multicenter studies would be helpful in further elucidating the risk profile of patient characteristics and coronary artery arrangements to determine whether routine use of SPCMR is warranted for TGA patients.

We report an interesting incidental liver finding during ECG-gated cardiac computed tomography (CT) in a newborn with infracardiac total anomalous pulmonary venous connection to the portal vein. This case shows a unique abnormality in hepatic perfusion that was initially mistaken for hepatic vein thrombosis. We review the altered hepatic blood flow distribution in this pathologic anatomy to help explain the observed hepatic perfusion abnormality on CT. This understanding will enable an imager to anticipate hepatic perfusion patterns in similar patients, potentially avoiding misdiagnosis and unnecessary further testing.

Background To investigate the ability of a delayed respiratory-navigated, electrocardiographically-gated three-dimensional inversion recovery-prepared fast low-angle shot (3D IR FLASH) sequence to evaluate the lower airways in children undergoing routine cardiovascular magnetic resonance (CMR). Methods This retrospective study included pediatric patients (0–18 years) who underwent clinical CMR where a delayed 3D IR FLASH sequence was performed between July 2020 and April 2021. The airway image quality and extent of lower airway visibility were graded by two blinded readers using a four-point ordinal scale (0–3). Lower airway anatomical variants and abnormalities were recorded. Results One hundred and eighty patients were included with a median age of 11.7 (4.6–15.3) years. Fifty-one of 180 (28%) were under general anesthesia. Overall, the median grading of airway image quality was 3 (2–3) and the extent of lower airway visibility was 3 (3–3). Interrater agreement was almost perfect (κ = 0.867 and κ = 0.956, respectively). Image quality correlated with extent of lower airway visibility (r = 0.62, p < 0.01). Delayed 3D IR FLASH was able to characterize the segmental bronchi in 137/180 (76%) and lobar bronchi in 172/180 (96%) of patients. Lower airway abnormalities were identified in 37/180 (21%) of patients and 33/129 (26%) with congenital heart disease (CHD). Identified abnormalities included tracheobronchial branching anomalies in 6/180 (3%), abnormal tracheobronchial situs in 6/180 (3%), and extrinsic vascular compression in 25/180 (14%). Conclusion Delayed 3D IR FLASH has excellent performance for evaluation of the lower airway anatomy and can simultaneously assess for myocardial late gadolinium enhancement. Lower airway abnormalities are not infrequently seen in children undergoing routine CMR for CHD.

Despite the range of body sizes in children, few ventricular assist devices (VAD) exist to support pediatric patients with end-stage heart failure. Large registry data identified weight < 20 kg to be associated with higher rates of VAD-related stroke, compared to > 40 kg. Moreover, patients < 1 years of age experience the highest post-implant mortality, with 1-year survival improving in an age-dependent manner. Within different VAD types, intracorporeal continuous (IC) devices confer the greatest clinical benefit and quality of life compared to paracorporeal alternatives. The major limitation of IC VADs is the technical challenge of implantation into patients of small body size, thus the majority of patients with IC devices are pre-adolescents or older. However, since 2021, the use of HeartMate 3™ (HM3) has expanded to patients as small as 17.7 kg. Although HM3 offers equally favorable survival outcomes irrespective of body size, patients of low body surface area are more likely to experience non-device-related major infections and renal dysfunction, with suggestion for elevated risk of major bleeding and stroke. Innovative imaging strategies have emerged to assess the feasibility of HM3 implantation and facilitate preoperative planning in small children. Moreover, the unmet need for an IC device in the infant population has revived interest in the axial pump, with a pivotal clinical trial currently underway. VAD outcomes in the pediatric population are not equivalent across all ages and body sizes, thus size-stratified analyses and device development to serve the full spectrum of body habitus are key considerations as this field rapidly evolves.

Open heart surgery requires a proper understanding of the endocardial surface of the heart and vascular structures. While modern four-dimensional (4D) imaging enables excellent dynamic visualization of the blood pool, endocardial surface anatomy has not routinely been assessed. 4D image data were post-processed using commercially available virtual reality (VR) software. Using thresholding, the blood pool was segmented dynamically across the imaging volume. The segmented blood pool was further edited for correction of errors due to artifacts or inhomogeneous signal intensity. Then, a surface shell of an even thickness was added to the edited blood pool. When the cardiac valve leaflets and chordae were visualized, they were segmented separately using a different range of signal intensity for thresholding. Using an interactive cutting plane, the endocardial surface anatomy was reviewed from multiple perspectives by interactively applying a cutting plane, rotating and moving the model. In conclusions, dynamic three-dimensional (3D) endocardial surface imaging is feasible and provides realistic simulated views of the intraoperative scenes at open heart surgery. As VR is based on the use of all fingers of both hands, the efficiency and speed of postprocessing are markedly enhanced. Although it is limited, visualization of the cardiac valve leaflets and chordae is also possible.

Background: Most patients with significant left ventricular (LV) hypoplasia undergo single ventricle (SV) palliation, but biventricular (Bi-V) repair is viable in some patients with borderline LV hypoplasia. We sought to identify CMR (cardiovascular magnetic resonance) criteria predictive of successful primary Bi-V repair in neonates with borderline LV hypoplasia without significant stenosis of the mitral valve (MV) and aortic valve (AV), and to determine reasons for reintervention after successful Bi-V repair. Methods: This retrospective study included all patients with borderline LV hypoplasia who underwent CMR from 2003-2024 for surgical decision-making. Patients with abnormal segmental connections, atrioventricular septal defects, unrestrictive ventricular septal defects, those with more than mild MV stenosis (mean Doppler flow gradient > 5 mmHg) and/or more than mild AV stenosis (peak Doppler flow gradient >20 mmHg) were excluded. Patients were divided into two groups based on initial intervention - primary Bi-V repair and hybrid/ other staging procedure. Outcomes were categorized as successful primary Bi-V repair, successful staged Bi-V repair and failure to achieve Bi-V repair (hybrid followed by SV palliation, transplant, death). Fisher exact test and Mann-Whitney U test was utilized to explore potential relationships. ROC curves were used to test diagnostic accuracy of parameters to predict successful primary Bi-V repair. Results: Among 37 patients meeting the inclusion criteria, 23 (62%) patients underwent successful primary Bi-V repair, 8 (22%) underwent staged Bi-V repair, 6 (16%) failed to achieve Bi-V repair. Patients who underwent successful primary/ staged Bi-V repair had higher values for left ventricular diastolic volume index (LVEDVi 28 mL/m2 vs. 17.4.00 mL/m2; p <0.002), higher blood flow volume through the ascending aorta (QAo:1.99 L/min/m2 vs. 0.97 L/min/m2, p <0.012), and QAo / superior vena cava (QSVC) flow ratio (1.44 vs. 0.85, p =0.034) compared to those who had failure to achieve Bi-V repair. CMR LVEDVi cutoff of CMR 27 mL/m2, had 87% sensitivity and 79% specificity with an AUC of 87.6% and QAo threshold of 1.9 L/min/m2 had 65.2% sensitivity and 92.9% specificity (AUC: 86.0%) to predict successful primary Bi-V repair. Of 31 patients with primary or staged Bi-V repair, 7 (22%) underwent reinterventions for LVOT obstruction followed by mitral stenosis. Conclusions: CMR plays a critical role in pre-operative evaluation, surveillance and decision-making in patients with borderline LV hypoplasia. In patients with borderline LV hypoplasia without MV/AV stenosis, successful primary Bi-V repair can be achieved when the CMR-derived LVEDVi is >27 mL/m2 and QAo is > 1.99 L/min/m2.

Objective: Hands-on surgical training (HOST) for congenital heart surgery (CHS), utilizing silicone-molded models created from 3D-printing of patients’ imaging data, was shown to improve surgical skills. However, the impact of repetition and frequency of repetition in retaining skills has not been previously investigated. We aimed to longitudinally evaluate the outcome for HOST on two example procedures of different technical difficulties with repeated attempts over a 15-week period. Methods: Five CHS trainees were prospectively recruited. Repair of coarctation of the aorta (CoA) and arterial switch operation (ASO) were selected as example procedures of relatively low and high technical difficulty. Procedural time and technical performance (using procedure-specific assessment tools by the participant, a peer-reviewer, and the proctor) were measured. Results: Coarctation repair performance scores improved after the first repetition but remained unchanged at the follow-up session. Likewise, CoA procedural time showed an early reduction but then remained stable (mean [standard deviation]: 29[14] vs 25[15] vs 23[9] min at 0, 1, and 4 weeks). Conversely, ASO performance scores improved during the first repetitions, but decreased after a longer time delay (>9 weeks). Arterial switch operation procedural time showed modest improvements across simulations but significantly reduced from the first to the last attempt: 119[20] versus 106[28] min at 0 and 15 weeks, P = .049. Conclusions: Complex procedures require multiple HOST repetitions, without excessive time delay to maintain long-term skills improvement. Conversely, a single session may be planned for simple procedures to achieve satisfactory medium-term results. Importantly, a consistent reduction in procedural times was recorded, supporting increased surgical efficiency.

Purpose of review In the ever-evolving field of medical imaging, this review highlights significant advancements in preoperative and postoperative imaging for Tetralogy of Fallot (TOF) and double outlet right ventricle (DORV) over the past 18 months. Recent findings This review showcases innovations in echocardiography such as 3D speckle tracking echocardiography (3DSTE) for assessing right ventricle-pulmonary artery coupling (RVPAC) and Doppler velocity reconstruction (DoVeR) for intracardiac flow fields evaluation. Furthermore, advances in assessment of cardiovascular anatomy using computed tomography (CT) improve the integration of imaging in ablation procedures. Additionally, the inclusion of cardiac magnetic resonance (CMR) parameters as risk score predictors for morbidity, and mortality and for timing of pulmonary valve replacement (PVR) indicates its significance in clinical management. The utilization of 4D flow techniques for postoperative hemodynamic assessment promises new insights into pressure mapping. Lastly, emerging technologies such as 3D printing and 3D virtual reality are expected to improve image quality and surgical confidence in preoperative planning. Summary Developments in multimodality imaging in TOF and DORV are poised to shape the future of clinical practice in this field.