Pulmonary vascular resistance, collateral flow, and ventricular function in patients with a Fontan circulation at rest and during dobutamine stress.
BACKGROUND
The role, interplay, and relative importance of the multifactorial hemodynamic and myocardial mechanisms causing dysfunction of the Fontan circulation remain incompletely understood.


RESULTS
Using an MRI catheterization technique, we performed a differential analysis of pulmonary vascular resistance and aortopulmonary collateral blood flow in conjunction with global ventricular pump function, myocontractility (end-systolic pressure-volume relation), and diastolic compliance (end-diastolic pressure-volume relation) in 10 patients with a Fontan circulation at rest and during dobutamine stress. Pulmonary and ventricular pressures were measured invasively and synchronized with velocity-encoded MRI-derived pulmonary and aortic blood flows and cine MRI-derived ventricular volumes. Pulmonary vascular resistance and end-systolic and end-diastolic pressure-volume relations were then determined. Aortopulmonary collateral flow was calculated as the difference between aortic and pulmonary flow. Compared to rest, dobutamine caused a small increase in mean pulmonary pressures (P<0.05). Collateral flow was significantly augmented (P<0.001) and contributed importantly to an increase in pulmonary flow (P<0.01). Pulmonary vascular resistance decreased significantly (P<0.01). Dobutamine did not increase stroke volumes significantly despite slightly enhanced contractility (end-systolic pressure-volume relation). Active early relaxation (τ) was inconspicuous, but the end-diastolic pressure-volume relation shifted upward, indicating reduced compliance.


CONCLUSIONS
In patients with a Fontan circulation, aortopulmonary collateral flow contributes substantially to enhanced pulmonary flow during stress. Our data indicate that pulmonary vascular response to augmented cardiac output was adequate, but decreased diastolic compliance was identified as an important component of ventricular dysfunction.
Schmitt
Boris
B
Department of Congenital Heart Disease and Pediatric Cardiology, Deutsches Herzzentrum Berlin and The Charité, Medical University Berlin, Berlin, Germany,
Steendijk
Paul
P
Ovroutski
Stanislav
S
Lunze
Karsten
K
Rahmanzadeh
Pedram
P
Maarouf
Nizar
N
Ewert
Peter
P
Berger
Felix
F
Kuehne
Titus
T
D000293:Adolescent; D000328:Adult; D003097:Collateral Circulation; D003187:Compliance; D004280:Dobutamine; D015150:Echocardiography, Doppler; D017079:Exercise Tolerance; D018729:Fontan Procedure / Q000009:adverse effects*; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D009200:Myocardial Contraction; D011237:Predictive Value of Tests; D011652:Pulmonary Circulation; D016896:Treatment Outcome; D014655:Vascular Resistance; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D016276:Ventricular Function; D017725:Ventricular Pressure; D055815:Young Adult
D004280:Dobutamine