How to assess and treat right ventricular electromechanical dyssynchrony in post-repair tetralogy of Fallot: insights from imaging, invasive studies, and computational modelling

Biomechanical modeling combined with pressure-volume loop analysis to aid surgical planning in patients with complex congenital heart disease

Patients with congenitally corrected transposition of the great arteries (ccTGA) can be treated with a double switch operation (DSO) to restore the normal anatomical connection of the left ventricle (LV) to the systemic circulation and the right ventricle (RV) to the pulmonary circulation. The subpulmonary LV progressively deconditions over time due to its connection to the low pressure pulmonary circulation and needs to be retrained using a surgical pulmonary artery band (PAB) for 6-12 months prior to the DSO. The subsequent clinical follow-up, consisting of invasive cardiac pressure and non-invasive imaging data, evaluates LV preparedness for the DSO. Evaluation using standard clinical techniques has led to unacceptable LV failure rates of ∼15 % after DSO. We propose a computational modeling framework to (1) reconstruct LV and RV pressure-volume (PV) loops from non-simultaneously acquired imaging and pressure data and gather model-derived mechanical indicators of ventricular function; and (2) perform in silico DSO to predict the functional response of the LV when connected to the high-pressure systemic circulation. Clinical datasets of six patients with ccTGA after PAB, consisting of cardiac magnetic resonance imaging (MRI) and right and left heart catheterization, were used to build patient-specific models of LV and RV - MbaselineLV and MbaselineRV. For in silico DSO the models of MbaselineLV and MbaselineRV were used while imposing the afterload of systemic and pulmonary circulations, respectively. Model-derived contractility and Pressure-Volume Area (PVA) - i.e., the sum of stroke work and potential energy - were computed for both ventricles at baseline and after in silico DSO. In silico DSO suggests that three patients would require a substantial augmentation of LV contractility between 54 % and 80 % and an increase in PVA between 38 % and 79 % with respect to the baseline values to accommodate the increased afterload of the systemic circulation. On the contrary, the baseline functional state of the remaining three patients is predicted to be adequate to sustain cardiac output after the DSO. This work demonstrates the vast variation of LV function among patients with ccTGA and emphasizes the importance of a biventricular approach to assess patients' readiness for DSO. Model-derived predictions have the potential to provide additional insights into planning of complex surgical interventions.

Evolution of Right Ventricular Electromechanical Dyssynchrony During Childhood After Tetralogy of Fallot Repair

BACKGROUND

Patients with repaired tetralogy of Fallot (rTOF) develop electromechanical dyssynchrony (EMD), which detrimentally affects right ventricular (RV) function and exercise capacity. However, EMD evolution over childhood is unknown.

METHODS

We retrospectively studied serial ECG, Holter, echocardiography, cardiac magnetic resonance, and exercise data of rTOF patients, over the first 18-years of life, who underwent repair from 2010 to 2020. Mechanical dyssynchrony parameters were evaluated at ages 8-12 and 14-18 years.

RESULTS

A total of 95 patients (61% male) were followed for a median 15.7 years (range 8-18 years). QRS duration (QRSd) increased steeply in the first 6 years and gradually through adolescence. Prolonged QRSd was associated with decreased VO2 (P = 0.001), peak workload (P = 0.008), and RV ejection fraction (RVEF). RVEF decreased by 1.3% (-0.7 to -1.9) for every 10 ms increase in QRSd (P < 0.001). Patients with QRSd z score > 2 had a declining RVEF, despite a stable pulmonary insufficiency fraction and indexed RV end-diastolic volume throughout childhood. QRS fractionation (fQRS) increased during the first 6 years and then again in adolescence, which temporally coincided with the onset of arrhythmias. fQRS was associated with decreased RVEF (odds ratio [OR] 0.94; 95% confidence interval [CI] 0.9-1; P = 0.05) and RV longitudinal strain (OR 1.02; 95% CI 1.01-1.04; P = 0.008). 70.5% of patients had a septal flash at the first mechanical dyssynchrony assessment, which was associated with longer QRSd (median 124 ms [interquartile range (IQR) 107-136 ms] vs 100 ms [IQR 93-118 ms]; P = 0.019).

CONCLUSIONS

Electrical dyssynchrony is associated with progressive RV dysfunction and exercise intolerance over the course of childhood in rTOF, independently from pulmonary insufficiency. This raises the question of considering RV resynchronisation therapy in selected patients with symptomatic RV dysfunction and EMD.

Right Ventricular Electrophysiology and Arrhythmias in Adults With Congenital Heart Disease: Scientific Basis for Management

Right ventricular (RV) dysfunction and arrhythmias are major concerns in adults with congenital heart disease (CHD). The relationship between RV dysfunction and arrhythmogenesis is bidirectional, with structural and electrical remodeling contributing to arrhythmia development and, conversely, arrhythmias exacerbating RV failure. In addition to an RV in the standard subpulmonary position failing because of pressure and/or volume overload, other phenotypes associated with RV dysfunction in CHD include transposition of the great arteries with a systemic (subaortic) RV and univentricular hearts with a predominant RV morphology. The RV is better suited for low-pressure workloads. When it supports the systemic circulation, the RV undergoes remodeling changes that promote arrhythmias, which can provoke a cycle of worsening dysfunction and arrhythmogenesis. Arrhythmias can worsen RV dysfunction by impairing hemodynamic stability, reducing cardiac output, provoking dyssynchrony, and inducing tachycardia-induced cardiomyopathy. Cellular mechanisms, including myocardial fibrosis, dysregulation of ion channels, and abnormal gap junction function, are central to this process, facilitating both re-entrant and triggered arrhythmias. Conduction disturbances, whether inherent or caused by fibrosis or pacing, compound these effects, aggravating both RV dysfunction and arrhythmia perpetuation. Management strategies must be comprehensive and include pre-emptive approaches to minimize arrhythmias, alongside early detection. Individualized therapies may include catheter ablation and cardiac implantable electronic devices, with treatment tailored to the specific RV phenotype and arrhythmia type. In this review we emphasize the importance of personalized interventions to prevent the vicious cycle of RV dysfunction and arrhythmias in CHD. Further research is essential to optimize therapeutic strategies and address care-limiting knowledge gaps.

Digital Twins for Clinical and Operational Decision-Making: Scoping Review

BACKGROUND

The health care industry must align with new digital technologies to respond to existing and new challenges. Digital twins (DTs) are an emerging technology for digital transformation and applied intelligence that is rapidly attracting attention. DTs are virtual representations of products, systems, or processes that interact bidirectionally in real time with their actual counterparts. Although DTs have diverse applications from personalized care to treatment optimization, misconceptions persist regarding their definition and the extent of their implementation within health systems.

OBJECTIVE

This study aimed to review DT applications in health care, particularly for clinical decision-making (CDM) and operational decision-making (ODM). It provides a definition and framework for DTs by exploring their unique elements and characteristics. Then, it assesses the current advances and extent of DT applications to support CDM and ODM using the defined DT characteristics.

METHODS

We conducted a scoping review following the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) protocol. We searched multiple databases, including PubMed, MEDLINE, and Scopus, for original research articles describing DT technologies applied to CDM and ODM in health systems. Papers proposing only ideas or frameworks or describing DT capabilities without experimental data were excluded. We collated several available types of information, for example, DT characteristics, the environment that DTs were tested within, and the main underlying method, and used descriptive statistics to analyze the synthesized data.

RESULTS

Out of 5537 relevant papers, 1.55% (86/5537) met the predefined inclusion criteria, all published after 2017. The majority focused on CDM (75/86, 87%). Mathematical modeling (24/86, 28%) and simulation techniques (17/86, 20%) were the most frequently used methods. Using International Classification of Diseases, 10th Revision coding, we identified 3 key areas of DT applications as follows: factors influencing diseases of the circulatory system (14/86, 16%); health status and contact with health services (12/86, 14%); and endocrine, nutritional, and metabolic diseases (10/86, 12%). Only 16 (19%) of 86 studies tested the developed system in a real environment, while the remainder were evaluated in simulated settings. Assessing the studies against defined DT characteristics reveals that the developed systems have yet to materialize the full capabilities of DTs.

CONCLUSIONS

This study provides a comprehensive review of DT applications in health care, focusing on CDM and ODM. A key contribution is the development of a framework that defines important elements and characteristics of DTs in the context of related literature. The DT applications studied in this paper reveal encouraging results that allow us to envision that, in the near future, they will play an important role not only in the diagnosis and prevention of diseases but also in other areas, such as efficient clinical trial design, as well as personalized and optimized treatments.