Background Maladaptive remodelling mechanisms occur in patients with repaired tetralogy of Fallot (rToF) resulting in a cycle of metabolic and structural changes. Biventricular shape analysis may indicate mechanisms associated with adverse events independent of pulmonary regurgitant volume index (PRVI). We aimed to determine novel remodelling patterns associated with adverse events in patients with rToF using shape and function analysis. Methods Biventricular shape and function were studied in 192 patients with rToF (median time from TOF repair to baseline evaluation 13.5 years). Linear discriminant analysis (LDA) and principal component analysis (PCA) were used to identify shape differences between patients with and without adverse events. Adverse events included death, arrhythmias, and cardiac arrest with median follow-up of 10 years. Results LDA and PCA showed that shape characteristics pertaining to adverse events included a more circular left ventricle (LV) (decreased eccentricity), dilated (increased sphericity) LV base, increased right ventricular (RV) apical sphericity, and decreased RV basal sphericity. Multivariate LDA showed that the optimal discriminative model included only RV apical ejection fraction and one PCA mode associated with a more circular and dilated LV base (AUC = 0.77). PRVI did not add value, and shape changes associated with increased PRVI were not predictive of adverse outcomes. Conclusion Pathological remodelling patterns in patients with rToF are significantly associated with adverse events, independent of PRVI. Mechanisms related to incident events include LV basal dilation with a reduced RV apical ejection fraction.

Introduction: “Le Coeur en Sabot” (or the boot-shaped heart) is a radiological description of the appearance of the heart on a plain radiograph of a patient with Tetralogy of Fallot. This highlights the importance of the shape of the heart. Maladaptive remodeling is known to occur in patients with repaired Tetralogy of Fallot (rToF) due to residual lesions such as Pulmonary Regurgitant Fraction (PRF) Hypothesis: Shape and function analysis can reveal novel remodeling patterns associated with adverse events in patients with rToF Methods: Biventricular shape and function were studied in 192 patients with rToF (median age 15 years). Linear discriminative analysis (LDA) and principal component analysis (PCA) were used to identify shape differences between patients with and without adverse events (AE). AE included death, arrhythmias, and cardiac arrest (median follow-up 10 years) Results: LDA and PCA showed that shape characteristics pertaining to adverse events included a more circular LV (decreased eccentricity), dilated (increased sphericity) LV base, increased RV apical sphericity, and decreased RV basal sphericity. Multivariate LDA showed that the optimal discriminative model included only RV apical ejection fraction and one PCA mode associated with a more circular and dilated LV base (AUC = 0.78). PRF did not add value, and shape changes associated with increased PRF were not predictive of AE. Conclusions: Remodeling patterns in patients with rToF are associated with AE, independent of PRF. Mechanisms leading to AE include LV basal dilation with a reduced RV apical ejection fraction. That is to say that the old descriptor, “Le Coeur en Sabot'' may also describe that shape that is adverse in rTOF. The toe of this boot would be the dilated and poorly contractile RV apex and the ankle would be the spherical LV base (Figure 1: Top Row Diastole. Middle Systole. Posterior projection (a), anatomical position (b) and superior (c). LV is green)