Background
We hypothesize that dobutamine-induced stress impacts intracardiac hemodynamic parameters and that this may be linked to decreased exercise capacity in Fontan patients
.
Therefore, the purpose of this study was to assess the effect of pharmacologic stress on intraventricular kinetic energy (KE), viscous energy loss (EL) and vorticity from four-dimensional (4D) Flow cardiovascular magnetic resonance (CMR) imaging in Fontan patients and to study the association between stress response and exercise capacity.
Methods
Ten Fontan patients underwent whole-heart 4D flow CMR before and during 7.5 μg/kg/min dobutamine infusion and cardiopulmonary exercise testing (CPET) on the same day. Average ventricular KE, EL and vorticity were computed over systole, diastole and the total cardiac cycle (vorticity_vol
avg cycle
, KE
avg cycle,
EL
avg cycle
). The relation to maximum oxygen uptake (VO
2
max) from CPET was tested by Pearson’s correlation or Spearman’s rank correlation in case of non-normality of the data.
Results
Dobutamine stress caused a significant 88 ± 52% increase in KE (KE
avg cycle
: 1.8 ± 0.5 vs 3.3 ± 0.9 mJ,
P
< 0.001), a significant 108 ± 49% increase in EL (EL
avg cycle
: 0.9 ± 0.4 vs 1.9 ± 0.9 mW,
P
< 0.001) and a significant 27 ± 19% increase in vorticity (vorticity_vol
avg cycle
: 3441 ± 899 vs 4394 ± 1322 mL/s,
P
= 0.002). All rest-stress differences (%) were negatively correlated to VO
2
max (KE
avg cycle
:
r
= − 0.83,
P
= 0.003; EL
avg cycle
:
r
= − 0.80,
P
= 0.006; vorticity_vol
avg cycle
:
r
= − 0.64,
P
= 0.047).
Conclusions
4D flow CMR-derived intraventricular kinetic energy, viscous energy loss and vorticity in Fontan patients increase during pharmacologic stress and show a negative correlation with exercise capacity measured by VO
2
max.