Vivek Muthurangu

The value of exercise cardiovascular magnetic resonance (CMR) has been shown in many clinical scenarios. We have developed a novel MR‐compatible exercise device and aim to validate it against the reference standard MR‐conventional ergometer. The novel device consisted of two half‐pipes fixed to a wooden base, with participants wearing knee‐length socks with a 0.5 kg weight in each sock. Increased workload was achieved by increasing the rate of alternating leg flexion and extension in time with a bleep sound of increasing frequency. Twenty subjects (10 healthy volunteers, 10 patients with pulmonary arterial hypertension) performed two CMR‐augmented cardiopulmonary exercise tests (CMR/CPET) using the novel exercise device and a conventional ergometer in a randomised order. Comparing peak metrics elicited on both exercise devices, there was a moderate correlation in peak oxygen consumption (VO ₂ , r = 0.86, p < 0.001), cardiac output (CO, r = 0.73, p < 0.001), stroke volume (SV, r = 0.90, p < 0.001), peak heart rate (HR, r = 0.65, p = 0.002) and peak arteriovenous oxygen content gradient (ΔavO ₂ , r = 0.71, p < 0.001). However, all metrics were significantly lower with the novel device. Both devices were able to elicit statistically significant differences in VO ₂ , HR and right ventricular ejection fraction (RVEF) between patients and healthy subjects ( p ≤ 0.04). We have created a simple, easy to use and affordable exercise device for the CMR environment. This may encourage greater dissemination of exercise CMR in clinical and research practice.

BACKGROUND: Left ventricular ejection fraction (LVEF) independently predicts mortality in repaired tetralogy of Fallot (ToF), but the causes of LV dysfunction are incompletely understood. The intrinsic aortopathy of ToF increases pulsatile afterload, yet whether this contributes to LV dysfunction is unknown. We sought to determine whether aortic dimensions and flow-derived afterload act as cross-sectional markers of LV dysfunction, dynamic contributors to change in LV function over time, or both. METHODS: Retrospective longitudinal study of 554 patients with repaired ToF (1,448 serial cardiovascular magnetic resonance examinations, 2003-2026). Aortic root dimensions, total arterial compliance (TAC: aortic forward flow volume/pulse pressure), and systemic vascular resistance (SVR) were derived, and a within-between decomposition separated between-patient from within-patient associations with LVEF in mixed-effects models. RESULTS: In the analytic sample (1,053 observations, 521 patients), aortic sinus diameter predicted LVEF at both levels (within:β = -0.23, p<0.001; between: β = -0.20, p=0.003). Associations were reproduced at the sinotubular junction but absent at the ascending aorta, localising the effect to the root. TAC predicted LVEF within patients (β=0.90 per mL/mmHg, p=0.014) but not between patients (p=0.62), indicating that pulsatile afterload is a dynamic contributor to LV function. SVR predicted LVEF at both levels (within: β = -0.23; between: β = -0.25; both p<0.001). Blood pressure components alone, expressed as systolic and diastolic or as mean arterial and pulse pressure, did not predict LVEF and fitted the data less well. Adjustment for right ventricular ejection fraction attenuated the within-patient compliance association by 35%, suggesting a component shared with right ventricular function. CONCLUSIONS: Aortic root dimensions, TAC and SVR are independent longitudinal determinants of LVEF in repaired ToF, establishing an important role for aortic haemodynamics in LV function and identifying the systemic vasculature as a potentially modifiable contributor to LV dysfunction.

Aims: Survival following total cavopulmonary connection (TCPC) is influenced by pre-operative haemodynamics. We developed a minimally invasive method to measure total pulmonary resistance (TPR) at the bidirectional cavopulmonary connection (BCPC) stage, reflecting the combined pulmonary impedance of the TCPC circulation. We evaluated whether TPR predicted early Fontan failure [EFF; death, TCPC take-down, emergency fenestration, or mechanical circulatory support (MCS) ≤ 6months post-TCPC] or prolonged post-operative intensive care unit (ICU) stay (>14 days). Methods and results: TPR was derived using jugular venous pressure as a surrogate for central venous pressure (CVP) and pulmonary blood flow (Qp) measured non-invasively from cardiovascular magnetic resonance (CMR). Indexed TPR (TPRi) was calculated as CVP/Qp indexed to body surface area. Logistic regression evaluated predictors of early post-TCPC outcomes. Receiver operating characteristic (ROC) analysis assessed TPRi discrimination for EFF or the composite endpoint of EFF or prolonged ICU stay [early adverse outcome (EAO)]. Of 232 patients with BCPC undergoing CMR, 96% (n = 223) proceeded to TCPC. TPR data were available in 204 patients. On multivariable analysis, TPRi (adjusted OR 1.28, P = 0.030) and isomerism [adjusted odds ratio (OR) 14.34, P = 0.002] were independently associated with EFF. Both TPRi (adjusted OR 1.37, P = 0.001) and isomerism (adjusted OR 14.53, P = 0.001) also independently predicted EAO. ROC analysis identified optimal TPRi thresholds of ≥5.78 WU·m2 for EFF (sensitivity 80%, specificity 54%) and ≥5.7 WU·m2 for EAO (sensitivity 75%, specificity 53%). Conclusion: TPRi, calculated by combining pressure and flow data at the BCPC stage, independently predicts early adverse post-TCPC outcomes and may help identify high-risk patients without cardiac catheterization.

Aims: Weight-based regadenoson dosing for paediatric stress perfusion cardiac magnetic resonance (CMR) achieves coronary vasodilation but may result in excessive drug exposure in some patients. We evaluated the feasibility, safety, and diagnostic performance of heart rate-targeted regadenoson titration as an individualized alternative to fixed-based dosing. Methods and results: We performed a retrospective analysis of 31 consecutive regadenoson stress perfusion CMR studies (29 technically successful) in paediatric patients with known or suspected coronary artery disease (2015–2025). Regadenoson was administered incrementally, targeting ≥20% heart rate increase. Outcomes included achieved doses, haemodynamic responses, adverse events, image quality, and positivity rate. Results were compared with published weight-based dosing protocols.Mean age was 11.8 ± 4 years (range 3–18) and weight 50.4 ± 21 kg (range 14.9–91.8). Complete dosing data were available for 21/29 studies. Target heart rate response was achieved in all 29 studies (100% success) with a median dose 3.2 mcg/kg (range 1.6–8), representing 60% reduction compared with standard 8 mcg/kg protocols. Among patients >50 kg, 83% achieved adequate stress with ≤160 mcg (≤40% of the standard 400 mcg adult dose). Mean heart rate increased 42% (range 16–77%). Transient blood pressure reductions ≥10 mmHg occurred in nine patients. All studies yielded diagnostic-quality images. Stress-inducible perfusion defects were identified in 7/29 studies (24%). No major adverse events occurred. Conclusion: Heart rate-targeted regadenoson titration for paediatric stress perfusion CMR is feasible, achieving diagnostic-quality images with substantially reduced drug exposure. Consistent haemodynamic responses and positivity rates comparable to published series suggest adequacy of pharmacological stress, though prospective validation with quantitative perfusion measurement is required.

We introduce a deep learning framework comprising two models for automated segmentation (DCS) and large-scale deep temporal clustering (DTC) within a registry of single ventricle patients. The DCS model performs simultaneous classification and segmentation of velocity-encoded phase-contrast magnetic resonance (PCMR) data for five individual blood vessels, the left and right pulmonary arteries, aorta, superior vena cava, and inferior vena cava. Trained, validated and tested on 260 cardiac MRI exams (each containing 5 PCMR scans), it demonstrated a median Dice score of 0.91 on 50 unseen test exams. Integrated into a fully automated pipeline, the DCS model processed over 4500 registry exams without manual intervention, reaching 98% classification accuracy and 90% segmentation accuracy in cases with all five vessels present. Flow curves obtained from successful segmentations were used to train the DTC model, which performs deep temporal clustering to uncover unique flow patterns. Survival analysis showed that these groups were statistically correlated to increased risk of mortality or transplantation and to liver disease, highlighting the clinical relevance of the proposed framework.

Right ventricular (RV) failure is a principal determinant of morbidity and mortality in children with pulmonary hypertension, making accurate RV assessment a cornerstone of risk stratification and long-term management. Noninvasive imaging plays a central role in this evaluation; however, commonly used modalities, including 2- and 3-dimensional echocardiography and cardiac magnetic resonance imaging, each have distinct advantages and limitations in the pediatric population. Consequently, an integrated, multimodal imaging strategy is required. This review provides a contemporary, critical appraisal of the existing evidence and key knowledge gaps related to noninvasive multimodality imaging of the RV in pediatric pulmonary hypertension. The discussion is structured around fundamental aspects of RV physiology, including chamber size and mass, systolic function, diastolic function and stiffness, RV-left ventricle interactions, ventriculoarterial coupling, and exercise assessment. Echocardiography and cardiac magnetic resonance imaging are presented in parallel to highlight their complementary roles within a multimodality framework. Current prognostic thresholds in pediatric pulmonary hypertension imaging are largely supported by level of evidence C, underscoring persistent gaps that limit the development of definitive clinical recommendations and a unified approach. We propose a roadmap to guide future research efforts and collaborative initiatives among pediatric pulmonary hypertension and imaging specialists, emphasizing the role of professional networks in advancing the field.