Biomedical Engineering Reference
In-Depth Information
the azygos vein). While this outcome would be acutely positive in addressing the
right-sided PAVM, it is not a desirable long-term result as it presents a risk of future
left lung PAVM development. Two different HFD values are provided for option 3
because multiple Y-graft designs were created and evaluated, with the right branch
of the bifurcation being positioned slightly further to the right in one case (46 %)
than the other (0 %). This drastic difference in potential outcome made such an ap-
proach undesirable given the uncertainty in how precisely the surgeon can mimic
the virtual model in the operating room (i.e., the option was not robust with respect
to the exact detail of surgical implementation). Finally, option 4 took an alternative
approach to flow bifurcation by routing the right branch to the azygos vein (similar
to option 2) while maintaining the original hepatic connection to provide flow to
the left lung. Of the options tested, this design was predicted to yield the best out-
come (71 % HFD to the RPA with a 50
/
50 outflow split of the total flow imposed
as the boundary condition), presumably because it was successfully able to avoid
direct competition between the low momentum hepatic flow and high momentum
SVC/azygos flows. This 'H-graft' connection was ultimately selected for surgical
implementation and, although no post-operative image data are available, arterial
oxygen saturations were clinically seen to improve from 70 to 87 % four months
post-operatively, which is indicative of regression of the PAVM, as predicted.
16.3 Conclusions
Through multi-disciplinary research collaborations and technological develop-
ments, image-based computational surgery planning for the Fontan procedure has
become a reality. This ability greatly increases the resources available to clinicians
in patient-specific decision making by supplementing intuition and experience with
modeled predictions tailored to the specific case and intervention of interest. Obvi-
ously, these techniques have potential to extend far beyond Fontan surgery into the
broader realm of cardiovascular procedures, but to do so requires a similar under-
standing of the specific hemodynamic end points that mediate the desired clinical
outcome (as HFD relates to PAVM). Furthermore, surgical planning for the Fontan
is still in its preliminary stages and much work remains to be done, perhaps most im-
portantly, developing and validating the means of predicting what the post-operative
boundary conditions will be. Nevertheless, the novelty and value of these techniques
in translating engineering principles into actionable clinical tools are clear and the
present an exciting new paradigm for cardiothoracic modeling and interventions.
Acknowledgements
This work was supported by the National Heart, Lung, and Blood Institute
through Grants HL67622 and HL098252, and through American Heart Association Pre-Doctoral
Fellowships.
