Abstract 2207: Significant Impact of the Total Cavopulmonary Connection Resistance on Cardiac Output and Exercise Performance in Single Ventricles

Abstract

Introduction: The resistance of the total cavopulmonary connection (TCPC) in single ventricle (SV) circulation has long been hypothesized as a critical contributing factor to their diminished exercise capacity. We investigate this hypothesis using a lumped parameter (LP) model coupled with cardiac catheterization (cath) and computational fluid dynamics (CFD). Methods: SV pulmonary vascular resistance (1.80 ± 0.83 WU) and systemic vascular resistance (18.4 ± 7.2 WU) were obtained from cath data on 48 pts with a TCPC. TCPC resistances (0.55 ± .24 WU, min=0.24, max = 0.93) were established from CFD simulations (n=13) and in vitro experiments (n=8) conducted on anatomically accurate TCPC models from MRI. Resistance and compliance values for the normal pediatric circulation were obtained from the literature. These values were then used in a LP model developed for both the normal and SV circulation. Results: For a biventricular circulation, the cardiac output (CO) dependence on resistance is negligible, but not for the SV circulation (Fig 1a ). Capacity to increase CO with heart rate is also severely reduced for the SV. At a simulated exercise HR of 140 beats per minute, the SV patient with the highest resistance (0.93 WU) had a significantly lower increase in cardiac output (22%) when compared to an SV patient with the lowest resistance (26%) and the normal circulation (67%) (Fig 1b ). Conclusion: Hemodynamic energy cascade in a SV circulation should not be judged by stereotypes of biventricular circulation. The impact of TCPC surgical pathway resistance on cardiac output at rest and exercise was significantly higher on SVs compared to biventricular circulation. Figure 1. Impact of TCPC resistance in single ventricle vs. normal circulation, specifically (a) resting cardiac output, and (b) exercise cardiac output