Heart beat but not respiration is the main driving force of the systemic venous return in the Fontan circulation

Abstract

The Fontan procedure provides relief from cyanosis in patients with univentricular hearts. A major clinical unmet need is to understand whether the venous flow patterns of the Fontan circulation lead to the development of congestive hepatopathy and other life-threatening complications. Currently, there is no consensus on whether heart beat or respiration is the main driving force of venous return and which one affects the periodic flow changes for the most (i. e., pulsatility). The present study, for the first time, quantified respiratory and cardiac components of the venous flow in the inferior vena cava (IVC) of 14 Fontan patients and 11 normal controls using a novel approach (“physio-matrix”). We found that in contrast to the normal controls, respiration in Fontan patients had a significant effect on venous flow pulsatility, and the ratio of respiration-dependent to the cardiac-dependent pulsatility was positively associated with the retrograde flow. Nevertheless, the main driving force of net IVC flow was the heart beat and not respiration. The separate analysis of the effects of respiration and heart beat provides new insights into the abnormal venous return patterns that may be responsible for adverse effects on liver and bowel of the patients with Fontan circulation.

5D Flow MRI: A Fully Self-gated, Free-running Framework for Cardiac and Respiratory Motion–resolved 3D Hemodynamics

“…Respiratory-resolved analyses suggested increased peak velocity and net flow in the SVC and decreased peak and net flow in the IVC at Resp4. Although the influence of respiration on cardiopulmonary flow has been investigated for decades, the exact relationship is still unclear (1,23,24). The varying effects of respiration reported in this study and in previous studies suggest that studies with more respiratory bins are warranted.…”

Object‐Oriented Lumped‐Parameter Modeling of the Cardiovascular System for Physiological and Pathophysiological Conditions

“…In this case study, we present a lumped‐parameter representation of the Fontan circulation to illustrate the role that respiration alone plays on the hemodynamics of venous return, as recently demonstrated in vivo. [ 84 ] This work concluded that breathing, rather than the pumping action of the heart, is responsible for the flow characteristics observed in the IVC in this patient population. By comparing the IVC hemodynamics obtained in silico, we aim to further demonstrate the versatility of our proposed platform.…”

“…[ 80 ] Although this surgery prolongs life, hemodynamic abnormalities result from this procedure, and the resulting single ventricle physiology, including low pulsatile flow within the inferior vena cava (IVC) and elevated hepatic venous pressures, which can lead to a host of long‐term morbidities and mortality. [ 81–84 ]…”

“…By matching the average respiratory rate and cardiac output of the patient population in the clinical study, we closely replicated the breathing gating analysis. [ 84 ] The geometrical characteristics of the heart chambers were modified from the baseline simulation to more accurately reproduce cardiac anatomy in hypoplastic left heart syndrome. Finally, the thoracic IVC was replaced with a simulated Dacron shunt to mimic that typically implanted during the surgical procedure, [ 85,86 ] and pulmonary resistances were increased to model pulmonary hypertension, which is highly prevalent in Fontan patients.…”

“…b) Schematic of the benchtop simulator used for validation. c) Comparison of Fontan hemodynamics across our in silico model, in vitro platforms and in vivo study, [ 84 ] showing the characteristic low pulsatile flow within the IVC.…”