Ventricular outflow tract obstruction: An in-silico model to relate the obstruction to hemodynamic quantities in cardiac paediatric patients

Figures

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  Fig 1. (a) Scheme of the ventricular outflow tract simulated as a one-dimensional flow in a circular pipe of diameter D and area A. The obstruction reduces the cross-sectional area to the minimum Afree. (b) Streamlines of the flow and the pressure grade line (red dotted line) due to the presence of the obstruction. The obstruction causes a pressure drop which is only partially recovered in the downstream section, determining a pressure gradient Δpobs. Eddies are present only on the downward section toward the artery. Q, the flow rate, pLV (pRV), pressure in the left (right) ventricle, and pobs, pressure distal to the obstruction.

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  Fig 2. Streamlines of the flow due to the presence of an ideal round obstruction.

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  Fig 3. Panel (a): 0D model results for the physiologic case (aortic pressure, red curve; aortic flow rate, blue curve). Panels (b) and (c): published in-vivo data (aortic Doppler velocity waveform [19] and aortic pressure [20]). Note that, by assuming a constant valve area, the velocity waveform resembles the flow one except for the absolute values and the scale.

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  Fig 4. Panel (a): 0D model results for the physiologic case (pulmonary arterial pressure, red curve; pulmonary flow rate, blue curve). Panels (b): [22] and (c): [23] published data (pulmonary Doppler velocity waveform and pulmonary arterial pressure, respectively). Note that, by assuming a constant valve area, the velocity waveform resembles the flow one except for the absolute values and the scale.

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  Fig 5. Left ventricle pressure (green), aortic pressure (red), and aortic flow rate (blue) as calculated by the model for the physiologic case (panel (a)) and the case of obstruction located in the LVOT with Afree/A = 0.525 (panel (b)).

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  Fig 6. Pulmonary arterial pressure and flow rate. (a) computed pulmonary arterial pressure, (b) stenotic reference data (blue and red, right ventricular and pulmonary arterial pressure, respectively) [25], (c) computed pulmonary flow rate, and (d) stenotic reference data [22]. For the computed waveforms: in red, the healthy condition, and in blue, the stenotic case.

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  Fig 7. Computed mean (red filled dotted line) and peak (orange open dotted line) pressure gradient for (a) LVOT and (b) RVOT. Dashed lines depict possible thresholds for moderate/severe obstruction, inferred from the literature for the case of a tumoral obstructive condition as it follows: mean gradient 30 mmHg [32] and 35 mmHg [31], red lines; peak gradient 50 mmHg [33] and 60 mmHg [31], orange lines.

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  Fig 8. Cardiac output (CO) reduction as the obstruction worsens for LVOT (blue) and RVOT (red) obstructions.

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  Fig 9. Computed mean pressure gradient with (red filled dotted line, Δpobs) and without (green filled dotted line, ΔpDoppler) the pressure recovery effect for (a) LVOT and (b) RVOT. Red dashed lines depict possible mean gradient thresholds for moderate/severe obstruction, inferred from the literature for the case of a tumoral obstructive condition as it follows: 30 mmHg [32] and 35 mmHg [31].