Short‐Term Effects of Inhaled Nitric Oxide on Right Ventricular Flow Hemodynamics by 4‐Dimensional–Flow Magnetic Resonance Imaging in Children With Pulmonary Arterial Hypertension

Figures

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  Figure 1. Representation of the intracardiac particle tracking visualization in the right ventricle (RV) and left ventricle (LV) throughout the cardiac cycle. Four components of the end‐diastolic volume are color coded as follows: green, direct flow; blue, retained inflow; yellow, delayed ejection flow; and red, residual volume.

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  Figure 2. Graphical comparison of the catheterization hemodynamics at baseline and during inhaled nitric oxide (iNO) challenge. There was a significant reduction in pulmonary vascular resistance index (PVRi) (A), mean pulmonary arterial pressure (mPAP) (B), and the right ventricular (RV) systolic pressure (SP) (C) on iNO administration. There was no difference in the RV diastolic pressure (DP) (D). Red lines represent the cases that met the Sitbon criteria for positive acute vasoreactivity test. WU indicates Wood unit.

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  Figure 3. Comparison of 4‐dimensional–flow magnetic resonance imaging particle tracking parameters between patients with pulmonary arterial hypertension (PAH) and controls. Top panels (A through D) show the comparison of the individual flow/end‐diastolic components in the right ventricle (RV). Patients with PAH had significantly decreased direct flow (A) when compared with controls and significantly increased residual volume (D) when compared with controls. There were no differences in the RV delayed ejection (B) and retained inflow (C). Bottom panels (E through H) show the identical analysis for the left ventricle (LV). Patients with PAH had significantly decreased direct volume (E) and increased residual volume (H), with no differences in the LV delayed volume (F) and retained inflow (G).

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  Figure 4. Comparison of qualitative flow analysis between representative patient with pulmonary arterial hypertension (PAH) and control subject. The right ventricular inflow patterns were similar between subjects with PAH and control subjects, with prominent vortices formed along each tricuspid leaflet (* marking vortex formed along the anterior and septal leaflets; posterior vortex is hindered in the 4‐chamber view). The left ventricular vortex was not fully developed in 4 patients with PAH but was present in all control subjects.

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  Figure 5. Changes in the right ventricular (RV) flow hemodynamic profile associated with nitric oxide challenge. A, Graphical representation of the effect of inhaled nitric oxide (iNO) challenge on the flow components derived by 4‐dimensional–flow magnetic resonance imaging tracking, measured in the RV. B, Pie chart representation of average values of the 4 flow components at baseline and after iNO challenge. C through F, Pairwise comparison of individual flow components. There was a significant increase in direct flow (C) from baseline on iNO administration, but the opposite effect was observed in the residual volume. There were no changes in delayed ejection and retained volume.

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  Figure 6. Changes in the left ventricular (LV) flow hemodynamic profile associated with nitric oxide challenge. A, Graphical representation of the inhaled nitric oxide (iNO) challenge on the flow components derived in the LV. B, Pie chart representation of average values of the 4 flow components at baseline and after iNO challenge. C through F, Pairwise comparison of individual flow components did not reveal any changes in the LV on iNO administration.

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  Figure 7. Linear regression analysis between the changes in primary catheterization hemodynamics of 4‐dimensional–flow magnetic resonance imaging derived individual flow components in the right ventricle. Changes in mean pulmonary arterial pressure (mPAP) were not associated with the change in direct flow (A) and residual volume (B). Similarly, change in the pulmonary vascular resistance index (PVRi) was not associated with direct flow (A) and residual volume (B). WU indicates Wood unit.