Abstract 14479: Fontan Patients With Dominant Left Ventricular Morphology Have Severe Ventricular Electromechanical Discoordination Associated With Worse Exercise Capacity

Introduction: Fontan patients with a single left ventricle (SLV) develop late systolic and diastolic dysfunction. The development of SLV dysfunction has been associated with abnormal loading conditions, myocardial ischemia and fibrosis, and compromised ventricular-aortic coupling. However, electromechanical discoordination, a prime determinant of ventricular performance, has not been adequately evaluated in patients with SLV. Hypothesis: Patients with SLV and Fontan circulation will have abnormal electromechanical discoordination compared to controls, and this will be associated with their functional status. Methods: Patients with SLV (n=20) and healthy controls (n=20) underwent MRI-based tissue deformation analysis. Circumferential strain and strain rate data were used to calculate systolic stretch fraction (SSF) and diastolic relaxation fraction (DRF) (Figure 1). SSF is the proportion of myocardial segments undergoing relaxation in systole, while the DRF is the proportion of myocardial segments undergoing contraction in diastole. SSF and DRF were correlated with standard MRI indices and standard exercise tests. Results: Global circumferential strain was decreased in SLV compared to controls (16.4±2.7 vs 19.9±1.7, P<0.001). SLV had increased median SSF when compared to the LV of controls [(0.023 (IQR: 0.006-0.036) vs. 0.007 (IQR: 0.006-0.013), P=0.023] and increased median DRF [0.39 (IQR: 0.30-0.44) vs. 0.30 (IQR: 0.26-0.32), P=0.002]. SSF correlated with the peak VO 2 index (R=-0.56, P=0.027) and DRF correlated with ejection fraction (R=-0.56, P=0.010). Conclusion: Fontan patients with SLV exhibit systolic and diastolic electromechanical discoordination, which is associated with lower peak VO 2 and reduced ejection fraction, respectively. Electromechanical discoordination might contribute to global SLV dysfunction by limiting both effective contractility and preload generation.