Effect of pannus formation on the prosthetic heart valve: In vitro demonstration using particle image velocimetry

Fig 1. Representative images showing a subvalvular pannus involving the prosthetic aortic valve. (A) Multiplanar CT reformation in profile view showing the subvalvular soft tissue below the posterior prosthetic valve (arrow) and decreased opening angle of the posterior leaflet. (B) Aortic valve in-plane view on CT showing circumferential involvement of the soft-tissue lesions (arrowheads) below the prosthetic valve around the strut. (C) High peak pressure gradient (140/100 mmHg) and peak velocity (6.2 m/s) through the aortic valve are noted on echocardiography. (D) The surgical specimen of the prosthetic valve showing the circumferential fibrous soft tissue, named as pannus (areas in the red dashed line), in the subvalvular area. The lesion is corresponded with the lucent area (B, arrows) detected on CT. AO, ascending aorta; LA, left atrium; LV, left ventricle.

Fig 2. Geometry of the aortic sinus model with the prosthetic valve. Effects of pannus involvement (Pannus 360° vs. Pannus 180°) were compared to the normal condition without pannus formation. (A) The aortic sinus model with the straight inlet. (B) The aortic sinus model with 25% inlet obstruction mimicking partial flow path obstruction by the septum were constructed. (C) Illustration of the prosthetic valve with pannus formation (red shade).

Fig 3. Schematics of the experimental set up. (A) Flow circuit system for PIV measurements. (B) Experimental set up for PIV measurement.

Fig 4. Waveform of the pulsatile inlet flow. Mean and maximum flow rate were 2.0 and 7.1 L/min, which corresponds to Remean = 779 and Remax = 2707, respectively. Note that the prosthetic valve is open during forward flow, and is closed by a slight portion of the retrograde flow.

Fig 5. Relationship between pannus formation and the opening angle of the prosthetic valve. (a) Estimation of maximum opening angle of the prosthetic valve at W/D = 0. Maximum opening angles of both leaflets during five cardiac cycles were used to obtained mean ± SE. (b) Effect of W/D on the maximum opening angle. Insets indicate opening of the mechanical valve at W/D = 0 and 0.25. All opening images of the prosthetic valve can be seen in S2 Fig.

Fig 6. Effects of pannus involvement (Pannus 360° vs. Pannus 180°) on the field behind the prosthetic valve at peak systole. Note that only results with the straight inlet case are shown and the results with 25% inlet obstruction are included in S3 Fig.

Fig 7. Relationship between W/D and NTPG. NTPG is obtained by dividing TPG by TPG obtained at W/D = 0. TPG at W/D = 0 was 2.1 mmHg.

Fig 8. Relationship between W/D and WSS at the aortic sinus. Note that Pannus 360° with W/D > 0.15 tends to produce positive WSS at the aortic sinus, whereas Pannus-180° produces negative WSS. Each data value indicates mean ± SE of WSS measured at the aortic sinus (AA).

Fig 9. Effects of pannus formation on principal shear stress and corresponding viscous energy loss behind the prosthetic heart valve. The numeric value of total viscous energy loss within the aortic sinus was shown right below the viscous energy loss mapping. Note that only results with the straight inlet case are shown and results with 25% inlet obstruction are included in S5 and S6 Figs.

Fig 10. Relationship between pannus formation and pressure drop across the prosthetic valve. (a) The relationship between the pressure drop and pannus width. (b) The relationship between the pressure drop and pannus area. The flow rate was fixed to constant of 6 L/min. Note that pressure ports for the pressure measurement were located at 70 and 65 mm in front and behind the pannus, respectively.

Fig 11. Graphical summary of pannus formation and its effects on valvular dysfunction and hemodynamics in the post-valve aortic sinus.