The Fontan Circulation: The Known, the Unknown and the Plausible
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CARDIOLOGY (WW LAI, SECTION EDITOR)
The Fontan Circulation: The Known, the Unknown and the Plausible Jacoba J. Louw • Marc Gewillig
Published online: 1 March 2013 Springer Science + Business Media New York 2013
Abstract The Fontan circulation is used as palliative surgery in the functionally univentricular heart. Due to the advances made in prenatal diagnosis, cardiac surgery, technology, and monitoring in complex congenital heart disease, survival rates have improved significantly. For this group of patients, the physiology and pathology remain challenging and eluding, even more so in the long-term follow-up. In the last decade pulmonary vascular resistance has been shown to be of utmost importance regarding cardiac output both at rest and during exercise. The aim of this article is to review the most recently published data, namely new concepts and our current understanding regarding the physiology; performance during exercise; the value of imaging modalities; and chronic liver pathology in the Fontan circulation. Keywords Fontan circulation Univentricular heart Single ventricle Cardiopathy Congenital heart disease Pulmonary vascular resistance
Introduction In mammals, the cardiovascular system consists of a double-circuit, pulmonary and systemic, connected in series
J. J. Louw M. Gewillig (&) Pediatric and Congenital Cardiology, University Hospitals Leuven, Herestraat 49, 3000 Leuven, Belgium e-mail: [email protected] J. J. Louw e-mail: [email protected]
and powered by a double pump. Many complex cardiac malformations are characterized by the existence of only one functional ventricle. At birth, in a functionally univentricular heart (UVH) the circulation cannot be connected in series but remains in parallel. This has two major disadvantages: arterial desaturation, both at rest and increasing during exercise, and a chronic volume overload to the single ventricle. This chronic volume overload will progressively impair the ventricular function, leading to a gradual attrition due to congestive heart failure from the third decade, with few survivors beyond the fourth decade. In 1971, Fontan and Baudet [1] from Bordeaux, France, reported a new approach to the operative treatment of the functionally UVH by separating the systemic and pulmonary circulation in a staged method. Advantages of a Fontan circuit include (near-) normalization of the arterial saturation, and abolishment of the chronic volume overload. However, because the flow to the heart is hindered by the pulmonary impedance, the price for such a circulation includes chronic ‘‘hypertension’’ and congestion of the systemic veins, with decreased cardiac output both at rest and during exercise. Furthermore, the Fontan ventricle has a bad reputation: it is known to be large, hypertrophic, hypo-contractile, and non-responsive to the usual means utilized to increase cardiac output. In recent years, our understanding of the physiology has changed considerably. We have learned that, once created, the Fontan circuit allows little modu
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