Hemodynamic Considerations after Coarctation Repair

Scriptie/masterproef: Doctoral Thesis

Uittreksel

Summary
CoA repair has been performed successfully since 1945. However, long-term
morbidity and mortality are still an important concern, mostly related to HT.
Besides the impact of variable clinical factors, greater insight into the aortic and
ventricular hemodynamics before and after CoA repair is essential to improve the
long-term perspective.
Via a systematic review (Chapter IV), we added to the knowledge-base on HT
after CoA repair by establishing that the prevalence is currently higher than
previously thought, depending on the definitions to categorize HT and the
methods of BP registration.
There is increasing recommendation to include 24h BP measurements to the
annual follow-of CoA patients to improve the sensitivity in diagnosing HT. The
review also revealed an increased incidence of obesity in CoA patients, promoting
HT.
Analysis demonstrated that peripheral BP as the simplest measure of afterload
has limited value in predicting central aortic hemodynamics and the real
magnitude of afterload. We highlighted novel non-invasive ways of estimating cSBP.
In our FSI study (Chapter V) we added to previous modelling studies by
incorporating the elasticity of the aorta. Comparison with CFD simulations
highlighted the importance of accounting for the elasticity of the aorta to correctly
capture the buffering capacity of the proximal aorta.
We found that the hemodynamic impact of an isolated stiffening is limited. Aortic
constriction, on the other hand, induces a pronounced increase in blood pressure
in the proximal aorta, buffering the stroke volume proximal to the aortic narrowing.
We concluded that for short constrictions, additional stiffening has a significant
impact on the pressure evolution, whereas the impact is relatively limited for
longer constricted segments. This helps us prioritize where different treatment
options are available.
Taking the boundary restrictions of computational models into account, a porcine
model of CoA (Chapter VI) allowed us to study the in-vivo effect of residual
lesions after CoA repair on ventriculo-arterial interaction.
The aortic hemodynamic findings of the former study were mostly confirmed, with
the addition that even a low gradient stenosis is associated with V-A impairment,
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which is further enhanced by inotropic stimulation. We concluded that the goal of
CoA repair is to pursue complete aortic remodelling with minimal hemodynamic
stenosis, even at the cost of inducing aortic stiffness.
In children after CoA repair, we found that diastolic dysfunction (and early systolic
dysfunction) is already present prior to developing HT. Exercise testing is a
method to identify alterations of ventricular and aortic hemodynamics early. In
Chapter VII, we validated the use of isometric exercise in children with CoA repair
based on handgrip loading, which allowed simultaneous evaluation of LV function
by echocardiography.
Finally, we went on to study cerebral and muscular tissue oxygenation with NIRS
technology during incremental exercise in children with aortic CoA (Chapter VIII).
We found diminished blood flow and oxygen transport at the level of the brain and
increased oxygen extraction at the level of the muscles during exercise. It is highly
likely that there is a greater reliance on O2 extraction because of the disturbed
balance between O2 supply and O2 demand even at low to moderate exercise
intensities.
Datum Prijs13 sep 2021
TaalEnglish
Toekennende instantie
  • Ghent University
BegeleiderDaniƫl De Wolf (Promotor)

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