Dominik Daniel Gabbert

Chronic pulmonary regurgitation (PR) after the repair of tetralogy of Fallot (TOF) and other right ventricular outflow tract (RVOT) interventions leads to progressive right ventricular (RV) dilatation, altered ventricular–ventricular interaction, and an increased risk of arrhythmia and heart failure. Pulmonary valve replacement (PVR), whether surgical or transcatheter, effectively eliminates or reduces PR and is associated with short- and mid-term improvement in RV size, symptoms, and electrocardiographic markers. However, the optimal timing of intervention remains unresolved: operating late can result in irreversible myocardial damage and arrhythmogenic substrates, whereas operating early can lead to repeated reinterventions, the impact of which on hard outcomes is uncertain. This review summarizes contemporary evidence on ventricular remodelling after PVR, focusing on cardiovascular magnetic resonance (CMR) and echocardiographic markers, and critically appraises proposed criteria for timing PVR. Classic CMR-derived thresholds (RV end-diastolic volume index [RVEDVi] 150–170 mL/m², RV end-systolic volume index [RVESVi] 80–90 mL/m²) and QRS duration cut-offs are discussed alongside emerging markers of risk, including the RV mass-to-volume ratio, diffuse myocardial fibrosis (extracellular volume fraction), strain imaging, and diastolic dysfunction. Meta-analyses show consistent reverse remodelling and symptomatic benefit after PVR, but no conclusive survival benefit has been demonstrated, and data on arrhythmic outcomes remain conflicting. Key gaps include (i) the lack of prospective randomized or carefully matched comparative studies of “early” versus “deferred” PVR; (ii) limited understanding of how myocardial fibrosis, RV hypertrophy, and diastolic dysfunction interact with volume load and timing to influence long-term outcomes; (iii) under-representation of adult and older adult TOF cohorts; and (iv) insufficient integration of multiparametric risk scores and machine-learning approaches into clinical decision-making. Future research should prioritize multicentre longitudinal cohorts with standardized imaging, electrophysiological and clinical endpoints, incorporate advanced imaging techniques (e.g., strain, 3D late gadolinium enhancement, and T1 mapping), and explore precision-medicine strategies to individualize PVR timing.

Staged palliation with the creation of a Fontan circulation is the standard surgical approach in patients with a single ventricle. The Fontan circulation is a complex circuit that is associated with various complications that may present early or later in life and can limit life quality and expectancy. In this context, a good understanding of the Fontan physiology is important to improve outcomes for single-ventricle patients. Cardiovascular magnetic resonance (CMR) is recommended for the long-term follow-up of Fontan patients, as it provides functional and haemodynamic information. Four-dimensional (4D) Flow MRI is a time-resolved, three-dimensional, velocity-encoded cardiovascular magnetic resonance technique that is increasingly used in Fontan patients because it not only enables measuring blood flow within a three-dimensional (3D) volume, but also allows for assessing more advanced haemodynamic parameters that may help in understanding the Fontan physiology and pathophysiology. Furthermore, 4D Flow is used for image-based simulations using computational fluid dynamics. In this review, we provide an overview of the use of cardiovascular magnetic resonance flow assessment, with a focus on four-dimensional flow (‘4D Flow’).

Objective: The prospect of being able to gain relevant information from cardiovascular magnetic resonance (CMR) image analysis automatically opens up new potential to assist the evaluating physician. For machine-learning-based classification of complex congenital heart disease, only few studies have used CMR. Materials and methods: This study presents a tailor-made neural network architecture for detection of 7 distinctive anatomic landmarks in CMR images of patients with hypoplastic left heart syndrome (HLHS) in Fontan circulation or healthy controls and demonstrates the potential of the spatial arrangement of the landmarks to identify HLHS. The method was applied to the axial SSFP CMR scans of 46 patients with HLHS and 33 healthy controls. Results: The displacement between predicted and annotated landmark had a standard deviation of 8–17 mm and was larger than the interobserver variability by a factor of 1.1–2.0. A high overall classification accuracy of 98.7% was achieved. Discussion: Decoupling the identification of clinically meaningful anatomic landmarks from the actual classification improved transparency of classification results. Information from such automated analysis could be used to quickly jump to anatomic positions and guide the physician more efficiently through the analysis depending on the detected condition, which may ultimately improve work flow and save analysis time.

Background: The status of the systemic right ventricular coronary microcirculation in hypoplastic left heart syndrome (HLHS) is largely unknown. It is presumed that the systemic right ventricle’s coronary microcirculation exhibits unique pathophysiological characteristics of HLHS in Fontan circulation. The present study sought to quantify myocardial blood flow by cardiac magnetic resonance imaging and evaluate the determinants of microvascular coronary dysfunction and myocardial ischemia in HLHS. Methods: One hundred nineteen HLHS patients (median age, 4.80 years) and 34 healthy volunteers (median age, 5.50 years) underwent follow-up cardiac magnetic resonance imaging ≈1.8 years after total cavopulmonary connection. Right ventricle volumes and function, myocardial perfusion, diffuse fibrosis, and late gadolinium enhancement were assessed in 4 anatomic HLHS subtypes. Myocardial blood flow (MBF) was quantified at rest and during adenosine-induced hyperemia. Coronary conductance was estimated from MBF at rest and catheter-based measurements of mean aortic pressure (n=99). Results: Hyperemic MBF in the systemic ventricle was lower in HLHS compared with controls (1.89±0.57 versus 2.70±0.84 mL/g per min; P P =0.446). Independent risk factors for a reduced hyperemic MBF were an HLHS subtype with mitral stenosis and aortic atresia ( P =0.017), late gadolinium enhancement ( P =0.042), right ventricular diastolic dysfunction ( P =0.005), and increasing age at total cavopulmonary connection ( P =0.022). The coronary conductance correlated negatively with systemic blood oxygen saturation (r, −0.29; P =0.02). The frequency of late gadolinium enhancement increased with age at total cavopulmonary connection ( P =0.014). Conclusions: The coronary microcirculation of the systemic ventricle in young HLHS patients shows significant differences compared with controls. These hypothesis-generating findings on HLHS-specific risk factors for microvascular dysfunction suggest a potential benefit from early relief of frank cyanosis by total cavopulmonary connection.

OBJECTIVES: This is a comprehensive analysis of haemodynamics after valve-sparing aortic root replacement (VSARR) with anatomically curved prosthesis (CP) compared to straight prosthesis (SP) and age-matched volunteers (VOL) using 4D flow MRI (time-resolved three-dimensional magnetic resonance phase-contrast imaging). METHODS: Nine patients with 90° CP, nine patients with SP, and twelve VOL were examined with 4D flow MRI. Analyses included various characteristic anatomical, qualitative and quantitative haemodynamic parameters. RESULTS: Grading of secondary flow patterns was lower in CP patients than in SP patients (P = 0.09) and more comparable to VOL, albeit not reaching statistical significance. However, it was easy to differentiate between VSARR patients and healthy volunteers: Patients more often had angular aortic arches (CP: 89%, SP: 100%; VOL: 17%; P ≤ 0.002), increased average curvature (CP: 0.17/cm [0.15, 0.18]; SP: 0.15/cm [0.14, 0.16]; VOL: 0.14/cm [0.13, 0.16]; P ≤ 0.007; values given as median [interquartile range]), and more secondary flow patterns (CP: 3 [2, 4] SP: 3 [2, 3] VOL: 2 [1, 2]; P < 0.01). Maximum circulation (CP: 142.7 cm2/s [116.1, 187.3]; SP: 101.8 cm2/s [77.7, 132.5]; VOL: 42.8cm2/s [39.3, 65.6]; P ≤ 0.002), maximum helicity density (CP: 9.6 m/s2 [9.3, 23.9]; SP: 9.7 m/s2 [8.6, 12.5]; VOL 4.9 m/s2 [4.2, 7.7]; P ≤ 0.007), and wall shear stress gradient (e.g., proximal ascending aorta CP: 0.97 N/m2 [0.54, 1.07]; SP: 1.08 N/m2 [0.74, 1.24]; VOL: 0.41 N/m2 [0.32, 0.60]; P ≤ 0.01) were increased in patients. One CP patient had a round aortic arch with physiological haemodynamic parameters. CONCLUSIONS: The restoration of physiological aortic configuration and haemodynamics was not fully achieved with the curved prostheses in our study cohort. However, there was a tendency towards improved haemodynamic conditions in the patients with curved prostheses overall but without statistical significance. A single patient with a CP and near-physiological configuration of the thoracic aorta underlines the importance of optimizing postoperative geometric conditions for allowing for physiological haemodynamics and cardiovascular energetics after VSARR.