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International Journal of Pediatrics
Volume 2010 (2010), Article ID 791291, 8 pages
http://dx.doi.org/10.1155/2010/791291
Review Article

What Limits Cardiac Performance during Exercise in Normal Subjects and in Healthy Fontan Patients?

1University Hospital, Catholic University of Leuven, 3000 Leuven, Belgium
2St Vincent's Hospital, University of Melbourne, 3065 Fitzroy, Australia

Received 16 February 2010; Revised 11 May 2010; Accepted 27 July 2010

Academic Editor: Patricia A. Nixon

Copyright © 2010 André La Gerche and Marc Gewillig. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Exercise is an important determinant of health but is significantly reduced in the patient with a univentricular circulation. Normal exercise physiology mandates an increase in pulmonary artery pressures which places an increased work demand on the right ventricle (RV). In a biventricular circulation with pathological increases in pulmonary vascular resistance and/or reductions in RV function, exercise-induced augmentation of cardiac output is limited. Left ventricular preload reserve is dependent upon flow through the pulmonary circulation and this requires adequate RV performance. In the Fontan patient, the reasons for exercise intolerance are complex. In those patients with myocardial dysfunction or other pathologies of the circulatory components, it is likely that these abnormalities serve as a limitation to cardiac performance during exercise. However, in the healthy Fontan patient, it may be the absence of a sub-pulmonary pump which limits normal increases in pulmonary pressures, trans-pulmonary flow requirements and cardiac output. If so, performance will be exquisitely dependent on pulmonary vascular resistance. This provides a potential explanation as to why pulmonary vasodilators may improve exercise tolerance. As has recently been demonstrated, these agents may offer an important new treatment strategy which directly addresses the physiological limitations in the Fontan patient.