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. 2022 Jun 30:13:867995.
doi: 10.3389/fphys.2022.867995. eCollection 2022.

Optimal Fenestration of the Fontan Circulation

Zan Ahmad  1 , Lynn H Jin  1   2 , Daniel J Penny  3 , Craig G Rusin  3 , Charles S Peskin  1 , Charles Puelz  1   3
Affiliations

Optimal Fenestration of the Fontan Circulation

Zan Ahmad et al. Front Physiol. .

Abstract

In this paper, we develop a pulsatile compartmental model of the Fontan circulation and use it to explore the effects of a fenestration added to this physiology. A fenestration is a shunt between the systemic and pulmonary veins that is added either at the time of Fontan conversion or at a later time for the treatment of complications. This shunt increases cardiac output and decreases systemic venous pressure. However, these hemodynamic benefits are achieved at the expense of a decrease in the arterial oxygen saturation. The model developed in this paper incorporates fenestration size as a parameter and describes both blood flow and oxygen transport. It is calibrated to clinical data from Fontan patients, and we use it to study the impact of a fenestration on several hemodynamic variables, including systemic oxygen availability, effective oxygen availability, and systemic venous pressure. In certain scenarios corresponding to high-risk Fontan physiology, we demonstrate the existence of a range of fenestration sizes in which the systemic oxygen availability remains relatively constant while the systemic venous pressure decreases.

Keywords: Fontan circulation; compartmental model; fenestration; hemodynamics; oxygen transport.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Sketches of the Fontan circulation in panel (A) and the fenestrated Fontan circulation in panel (B). Blue represents deoxygenated blood, red represents oxygenated blood, and purple represents a mixture of oxygenated and deoxygenated blood.
FIGURE 2
FIGURE 2
Results from our calibrated model with a closed fenestration. Three pressure waveforms from the end of the simulation are shown in panel (A) and a volume loop for the single ventricle is shown in panel (B). The end-systolic and end-diastolic parts of the pressure-volume loop are indicated by the red and black markers respectively.
FIGURE 3
FIGURE 3
Fenestration flow waveforms for two different fenestration sizes and our baseline pulmonary vascular resistance value of R p = 0.5517 mmHg min L−1. The waveform in panel (A) corresponds to a fenestration with diameter equal to 4 mm, and the waveform in panel (B) corresponds to a diameter of 8 mm.
FIGURE 4
FIGURE 4
Results corresponding to oxygen consumption equal to −0.3236 L min−1. Pulmonary resistance values R p centered around our baseline value are considered. Mean values for different hemodynamic and oxygen transport variables are plotted as functions of the fenestration diameter. (A) systemic flow, (B) systemic venous pressure, (C) fenestration flow, (D) venous oxygen saturation.
FIGURE 5
FIGURE 5
Results corresponding to oxygen consumption equal to −0.3236 L min−1. Pulmonary resistance values R p centered around our baseline value are considered. Mean values for different hemodynamic and oxygen transport variables are plotted as functions of the fenestration diameter. Note that both the systemic oxygen availability and effective oxygen availability curves are monotonically decreasing as the fenestration diameter increases. (A) pulmonary flow, (B) systemic arterial pressure, (C) arterial oxygen saturation, (D) systemic oxygen availability, (E) effective oxygen availability.
FIGURE 6
FIGURE 6
Results corresponding to oxygen consumption equal to −0.2 L min−1. Pulmonary resistance values R p larger than our baseline value are considered. Mean values for different hemodynamic and oxygen transport variables are plotted as functions of the fenestration diameter. (A) systemic flow, (B) systemic venous pressure, (C) fenestration flow, (D) venous oxygen saturation.
FIGURE 7
FIGURE 7
Results corresponding to oxygen consumption equal to −0.2 L min−1. Pulmonary resistance values R p larger than our baseline value are considered. Mean values for different hemodynamic and oxygen transport variables are plotted as functions of the fenestration diameter. Note that the systemic oxygen availability curves achieve an optimal value for a nonzero fenestration size. However, the effective oxygen availability, which is important for quantifying the supply of oxygen, monotonically decreases as the fenestration size increases. (A) pulmonary flow, (B) systemic arterial pressure, (C) arterial oxygen saturation, (D) systemic oxygen availability, (E) effective oxygen availability.
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