Nonlinear Power Loss During Exercise in Single-Ventricle Patients After the Fontan

Abstract

Background-We previously demonstrated that power loss (PL) through the total cavopulmonary connection (TCPC) in single-ventricle patients undergoing Fontan can be calculated by computational fluid dynamic analysis using 3-dimensional MRI anatomic reconstructions. PL through the TCPC may play a role in single-ventricle physiology and is a function of cardiac output. We hypothesized that PL through the TCPC increases significantly under exercise flow conditions. Methods and Results-MRI data of 10 patients with a TCPC were analyzed to obtain 3-dimensional geometry and flow rates through the superior vena cava, inferior vena cava, left pulmonary artery, and right pulmonary artery. Steady computational fluid dynamic simulations were performed at baseline conditions using MRI-derived flows. Simulated exercise conditions of twice (2ϫ) and three times (3ϫ) baseline flow were performed by increasing inferior vena cava flow. PL, head loss, and effective resistance through the TCPC were calculated for each condition. Each condition was repeated at left pulmonary artery/right pulmonary artery ratios of 30/70 and 70/30 to determine the effects of pulmonary flow splits on exercise PL. For each patient, PL increases dramatically in a nonlinear fashion with increasing cardiac output, even when normalized to calculate head loss or resistance. Flow splits had a significant effect on PL at exercise, with most geometries favoring right pulmonary artery flow. Conclusions-The relationship between cardiac output and PL is nonlinear and highly dependent on TCPC geometry and pulmonary flow splits. This study demonstrates the importance of studying the TCPC under exercise conditions, because baseline conditions may not adequately characterize TCPC efficiency.

The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

“…The patientspecific TCPC CFD analysis methodology and in vitro validations of these techniques have been described in previous studies (27,29,42). For each patient geometry, blood flow was modeled at baseline steady-state flow conditions by setting SVC and IVC flows to values derived from PC MRI averaged over the cardiac cycle.…”

“…A study by Szabo et al (40) reported increased E a and decreased E es as well using pressure-volume analysis conducted on measurements made in a dog SV model. In addition to experimental studies, theoretical models have also predicted similar changes in E a , E es , and cardiac reserve in a Fontan circulation (14,22,28).Most of the studies thus far on the Fontan circulation can be broadly categorized into two types: 1) those that study the Fontan circulation as a whole using in vivo animal and human studies (35,36,40); and 2) those that study the fluid mechanics of the surgically created TCPC in isolation from the SV circulation (27,41,42). There have not been many studies that have connected the two, i.e., those that relate the hemodynamics of the TCPC to upstream hemodynamics and cardiac function.…”

“…Most of the studies thus far on the Fontan circulation can be broadly categorized into two types: 1) those that study the Fontan circulation as a whole using in vivo animal and human studies (35,36,40); and 2) those that study the fluid mechanics of the surgically created TCPC in isolation from the SV circulation (27,41,42). There have not been many studies that have connected the two, i.e., those that relate the hemodynamics of the TCPC to upstream hemodynamics and cardiac function.…”

Pulmonary artery size and function after Fontan operation at a young age

“…Recent studies on the effects of exercise on caval vein and pulmonary artery flow after Fontan operation have emphasized the need for evaluation of the Fontan circulation under exercise conditions (15,16). In Fontan patients, PA flow has been studied directly after supine bicycle exercise with magnetic resonance imaging (MRI) (16).…”

Pulsatile venous waveform quality in Fontan circulation-clinical implications, venous assists options and the future

“…Recent attempts to quantify the pulsatility in Fontan patients revealed significant differences among different patient cohorts and suggested pulsatility as a promising parameter to predict late Fontan failure (10). Due to the absence of right heart active pumping source, minimized energy loss inside the total cavopulmonary connection (TCPC) pathway has been suggested for the best optimal surgical outcomes (11)(12)(13)(14). In our study, as the phase I step, we investigated the caval flow dynamics and the associated changes in pathway power loss for failing Fontan patients.…”