Impact of Ventricular Morphology on Fiber Stress and Strain in Fontan Patients

Background: Right ventricular (RV) morphology has been associated with adverse clinical outcomes in Fontan patients. The impact of RV versus left ventricular morphology on ventricular stress and strain in single ventricles is not well known. Methods and Results: Cardiac magnetic resonance examinations in 193 patients with the Fontan circulation were retrospectively analyzed. Ventricular mass, volume, global circumferential and longitudinal strain, and global average end-systolic fiber stress were calculated using previously published methods. Compared with left ventricular morphology, RV morphology (48%) was associated with higher ventricular end-diastolic volume (110 mL/BSA(1.3) versus 84 mL/BSA(1.3), P<0.001), lower mass-to-volume ratio (0.46 versus 0.57, P<0.001), higher global average end-systolic fiber stress (23 kPa versus 20 kPa, P=0.002), worse global circumferential strain (-21% versus -24%, P<0.001), and higher prevalence of greater than or equal to moderate atrioventricular valve regurgitation (25% versus 6%, P<0.001). Ejection fraction and global longitudinal strain were similar between the groups. Death or listing for heart transplantation occurred in 24 (12%) with a median follow-up of 6.2 years. On univariate analysis, RV morphology, ventricular dilatation, and worse global circumferential strain were associated with this composite outcome. Conclusions: In comparison to Fontan patients with a dominant left ventricle, those with a dominant RV have higher fiber stress, a higher rate of ventricular dilatation, lower circumferential fiber shortening, and similar longitudinal shortening. RV morphology, ventricular dilation, and worse circumferential strain are associated with death or heart transplantation. The difference in myofiber architecture may contribute to suboptimal adaptation of the RV as a systemic ventricle.