Biomedical Engineering Reference
In-Depth Information
between the geometric characteristics of the surgical construct and the resulting
patient-specific hemodynamics, which may relate to the numerous chronic morbidi-
ties seen in these patients. The combination of medical imaging, computer graphics
and computational fluid simulations has introduced a powerful new paradigm for
these procedures: providing the means to model the various options and evaluate
the resulting characteristics. This paper details these methodologies, their applica-
tion to planning interventions, and their contributions to generalizable knowledge
of Fontan hemodynamics.
16.1 Introduction
Single ventricle congenital heart defects are lethal if left untreated. The most com-
mon surgical intervention, known as the Fontan procedure, creates a right heart
bypass by routing systemic venous return to the pulmonary arteries (Fontan and
Baudet,
1971
), creating the total cavopulmonary connection (TCPC) (de Leval et al.,
1988
). Despite acceptable operative outcomes, significant long-term complications
are common, owing in part to the altered hemodynamics associated with Fontan
physiology (Mair et al.,
2001
). Such complications include arrhythmias, ventricular
dysfunction, exercise intolerance, protein-losing enteropathy, and pulmonary arteri-
ovenous malformations (PAVM) (Gersony and Gersony,
2003
).
Since its introduction, the TCPC has been the focus of large body of research in
an effort to understand how the geometric characteristics of the surgical construct
impact the hemodynamics within the connection (de Leval et al.,
1996
; Sharma
et al.,
1996
; Migliavacca et al.,
2003
; de Zélicourt et al.,
2005
). With only one ven-
tricle providing the driving pressure for both the systemic and pulmonary circula-
tions, the general motivation and hypothesis behind such studies are that minimizing
the hemodynamic power loss across the connection will provide long-term benefits
for cardiovascular health. While many early studies relied on relatively simple mod-
els of idealized geometries, the current state-of-the-art employs patient-specific data
for both the anatomic and physiologic boundary conditions for computational fluid
solvers.
Through such advances, in conjunction with progress in computer science and
free-form shape editing, it is now possible to both design and evaluate patient-
specific TCPC models (Pekkan et al.,
2008
). In other words, these engineering tools
can be used for prospective surgical planning by modeling any number of possible
anatomic variations and characterizing their associated hemodynamics. The appli-
cations of such methods extend equally well to either a patient's initial Fontan pro-
cedure or, as shown by Sundareswaran et al. (
2009a
) and de Zélicourt et al. (
2011
),
any subsequent surgical revisions, perhaps necessitated by deteriorating physiology
(i.e., Fontan failure). As such, these techniques represent a powerful new paradigm
for the approach to Fontan surgery and cardiothoracic surgery as a whole. The ob-
jective of this work is to detail the underlying methods and techniques upon which
surgical planning builds. Different examples of each method are provided through-
out to demonstrate their utility.
