Pulmonary Vascular Resistance, Collateral Flow, and Ventricular Function in Patients With a Fontan Circulation at Rest and During Dobutamine Stress

Abstract

Background-The role, interplay, and relative importance of the multifactorial hemodynamic and myocardial mechanisms causing dysfunction of the Fontan circulation remain incompletely understood. Methods and 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 (PϽ0.05). Collateral flow was significantly augmented (PϽ0.001) and contributed importantly to an increase in pulmonary flow (PϽ0.01). Pulmonary vascular resistance decreased significantly (PϽ0.01). Dobutamine did not increase stroke volumes significantly despite slightly enhanced contractility (end-systolic pressure-volume relation). Active early relaxation () 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. (Circ Cardiovasc Imaging. 2010;3:623-631.)

Aortopulmonary Collateral Flow is Related to Pulmonary Artery Size and Affects Ventricular Dimensions in Patients After the Fontan Procedure

“…The pulmonary vascular resistance (PVR) was calculated using the invasive pressure data and the CMR flows as the quotient between transpulmonary gradient and effective antegrade pulmonary flow defined as the sum of antegrade flow as measured in SVC and IVC plus collateral blood flow [8,10]. The transpulmonary gradient was calculated as the difference between mean pulmonary artery pressure and pulmonary capillary wedge pressure.…”

“…The observed inverse relationship between APC flow and vascular resistance indicates that additional pulsatile flow through APCs into the pulmonary vasculature seems not to increase, but even lowers pulmonary vascular resistance [10]. However, it has to be kept in mind that the mean follow-up after Fontan procedure was below 10 years and the long-term effect of these collaterals on the structure and remodelling of the distal pulmonary vascular bed remains unknown.…”

“…Data regarding the clinical implications of APCs in the midterm follow-up in patients with a total cavopulmonary connection (TCPC) is limited [4,9,10] but is of great interest as many centres routinely perform interventional closure of these collaterals.…”

Circulation: Cardiovascular Imaging Editors' Picks

“…The authors' 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. 10 Editor's Comment: Please refer to the comment following article In addition, this collateral flow was on average more than half of the total pulmonary blood flow and more than one third of the cardiac output (aortic flow), and ventricular end-diastolic volume correlated with collateral flow. This suggests that collateral flow can be a significant hemodynamic burden in this population.…”

Assessment of Hemodynamics by Magnetic Resonance Imaging

“…Geva et al evaluated cardiac function after surgery for TOF in patients by using MRI and reported the risk factors [14]. Schmitt evaluated cardiac function during exertion after the Fontan procedure in patients by using MRI [15]. As shown in the abovementioned and many other studies, cine MRI is used more often in the evaluation of cardiac function than is any other technique in cases of CHD [16,17].…”