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216 Rando et al. | Journal of Clinical and Translational Research 2024; 10(3): 212-218
alterations reported in humans with FTR, wherein the normally a rigid model with fixed geometry even after the application
saddle-shaped tricuspid annulus dilates and becomes more of surgical repairs. Perhaps the most comparable model was
circular [14-17]. We also observed alterations in the subvalvular proposed by Maisano et al., wherein a closed, pressurized
apparatus of the tricuspid valve, with significant increases in the circuit was developed using a centrifugal pump, and the porcine
anterior leaflet angle, tenting height, tenting area, and tenting right ventricle was dilated with sustained pressure [23]. The
volume. Historically, the importance of the subvalvular anatomy authors used radiopaque markers and fluoroscopy to document
of the tricuspid valve was not appreciated, and the emphasis the occurrence of tricuspid annular dilation, papillary muscle
was placed primarily on reducing the size of the tricuspid displacement, and induction of FTR after pressurizing the right
annulus to restore leaflet coaptation. Recent publications have ventricle. Our model requires fewer resources; the pneumatic
emphasized the importance of residual leaflet tethering as a pump and 3D light scanner required for this model are both
predictor of failure after tricuspid repair and have called for commercially available and comparatively inexpensive.
novel repair strategies that address both annular dilation and Furthermore, the 3D geometry of our model was directly
leaflet tethering [18-20]. Our ex vivo model of FTR incorporates compared to normal and diseased human TTE data in this study,
both of these geometric alterations and thus offers a realistic whereas the model suggested by Maisano et al. solely describes
platform for testing novel repair strategies. the geometric changes relative to the baseline.
When directly comparing geometric measurements between We acknowledge that this model has several limitations.
the ex vivo model and human TTE data, the majority of annular First, this is a static representation of the tricuspid valve at peak
dimensions remained similar. These results are consistent with systole and cannot be used to evaluate valvular anatomy in
both ex vivo and in vivo reports of porcine tricuspid anatomy. In diastole. We believe that the mid-systolic phase of the cardiac
an evaluation of 119 porcine hearts, Waziri et al. demonstrated cycle is the most clinically relevant to capture when evaluating
no difference in tricuspid annulus circumference or area the effectiveness of repair strategies for FTR. Tricuspid stenosis
compared to humans [21]. Similarly, Fawzy et al. evaluated is exceedingly uncommon and is unlikely to occur with the
the 3D geometry of the tricuspid annulus in anesthetized swine application of repair strategies for FTR, where the annulus has
using sonomicrometry and described similar annular dimensions already dilated from baseline. Even so, the diastolic performance
to humans [22]. These findings collectively demonstrate that the of novel repairs would need to be examined in vivo or with
native porcine tricuspid valve reasonably approximates that of a a dynamic, pulsatile ex vivo model. Second, preservation of
human, justifying its future utilization in translational research. the pericardium was not possible due to the manner in which
Our data demonstrated that the subvalvular apparatus of the the porcine hearts were harvested. Assessment of pericardial
porcine tricuspid valve was not directly comparable to that of a contributions to valvular geometry would be better assessed
human. At baseline, the porcine tricuspid valve had a narrower with an in vivo model. Furthermore, we employed a pneumatic
minor axis with steeper leaflet angles and greater tenting than model for pressurizing the right ventricle, potentially resulting
that of a human. As such, many of these differences persisted in different mechanics of valve closure than those observed with
after inducing FTR; the porcine valve had greater anterior and blood. The pneumatic model also limits our ability to assess
septal leaflet angles, tenting height, and tenting volume relative the right ventricle, as the structured light scanner used in this
to human TTE data. Given that our annular measurements model is restricted to the assessment of surface-level anatomy.
were comparable between the ex vivo model and human TTE Qualitative assessment of the right ventricle in the ex vivo model
data, the observed differences in subvalvular measurements before and after sustained pneumatic pressurization suggests
likely reflect differences in anatomy between species rather right ventricular dilatation as the source of increased tenting
than flaws in the ex vivo model itself. Surprisingly, no study angles with the induction of FTR, but this was not quantifiable.
has evaluated the differences in subvalvular anatomy between Similarly, the individual contribution of constituent elements of
swine and humans, despite numerous translational studies being the tricuspid valve was not assessed in this research. Previous
performed in porcine models. Despite these differences, the research has implicated the transition between the papillary
strength of this model lies in the geometric alterations observed muscle and chordae tendinae as a potential origin of valve
between the native and FTR states; although the subvalvular deformation [24,25], which may or may not be accurately
measurements were not identical between swine and humans, represented by the ex vivo model proposed herein. Finally, as
the directional and incremental changes between normal and mentioned above, it is important to take into consideration the
diseased specimens were similar. baseline differences in anatomy between swine and humans
Furthermore, our model compares favorably to those when interpreting results from this model. We observed modest
described by other groups in terms of validity, simplicity, and differences in subvalvular anatomy between swine and human
cost. Adkins et al. induced FTR in ovine hearts by injecting data. As such, any subvalvular geometric measurements sampled
95% phenol around the annulus to create annular dilation, in the ex vivo FTR model should be interpreted in reference to
but the degree of dilation was not validated and there was no ex vivo native measurements, and not to normal human TTE data.
alteration of the subvalvular apparatus [3]. Stock et al. isolated 5. Conclusion
porcine tricuspid valve complexes and mounted them on an
adjustable supporting device [4]. This allowed for replication The ex vivo porcine model of FTR characterized in this
of the geometric changes observed with FTR but provided study demonstrates consistent annular dilation and leaflet

DOI: https://doi.org/10.36922/jctr.24.00003