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

Right bundle branch block (RBBB) and resulting RV electromechanical discoordination are thought to play a role in the disease process of subpulmonary right ventricular (RV) dysfunction that frequently occur post-repair tetralogy of Fallot. We sought to describe this disease entity, the role of pulmonary re-valvulation and the potential added value of RV cardiac resynchronization therapy (RV-CRT). Two patients with repaired tetralogy of Fallot, complete right bundle branch block, pulmonary regurgitation and significantly decreased RV function underwent echocardiography, cardiac magnetic resonance, and an invasive study to evaluate the potential for RV-CRT as part of the management strategy. The data were used to personalize the CircAdapt model of the human heart and circulation. Resulting Digital Twins were analyzed to quantify the relative effects of RV pressure and volume overload and to predict the effect of RV-CRT. Echocardiography showed components of a classic RV dyssynchrony pattern which could be reversed by RV-CRT during invasive study and resulted in acute improvement in RV systolic function. The Digital Twins confirmed a contribution of electromechanical RV dyssynchrony to RV dysfunction and suggested improvement of RV contraction efficiency after RV-CRT. The one patient who underwent successful permanent RV-CRT as part of the pulmonary re-valvulation procedure carried improvements that were in line with the predictions based on his Digital Twin. We conclude, that an integrative diagnostic approach to RV dysfunction, including the construction of Digital Twins, may help to identify candidates for RV-CRT as part of the lifetime management of tetralogy of Fallot and similar congenital heart lesions.