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(Circulation. 2006;114:1226-1228.)
© 2006 American Heart Association, Inc.

Editorial

From Theory to Practice

Optimizing the Efficiency of an Inefficient Circulation

Doff B. McElhinney, MD; David F. Teitel, MD

From the Department of Cardiology, Children’s Hospital and Department of Pediatrics, Harvard Medical School, Boston, Mass (D.B.M.), and Department of Pediatrics, University of California at San Francisco (D.F.T.).

Correspondence to Doff B. McElhinney, MD, Department of Cardiology, Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. E-mail doff.mcelhinney@cardio.chboston.org

Key Words: Editorials • circulation • heart defects, congenital • pediatrics

An extract of the first 250 words of the full text is provided, because this article has no abstract.

In a study published in this issue of Circulation, Diller and colleagues¹ applied differential calculus to the model derived by Santamore et al² to explore the complex relationship between blood flow, arterial and venous oxygen content, and tissue oxygenation in patients with a bidirectional cavopulmonary shunt (BCPS). The BCPS is a unique and inherently inefficient circulatory arrangement that is used in the staged palliation of complex, functionally univentricular heart defects. In this circulation, pulmonary blood flow (Q_p) is supplied directly by venous return from the upper body via the superior vena cava (SVC), while venous return from the inferior vena cava and coronary sinus mixes with pulmonary venous blood. This mixed venous return, which varies in oxygen content according to the absolute and relative rates of Q_p and lower body blood flow, pulmonary and lower body systemic venous saturation, and oxygen carrying capacity, is then ejected to the systemic circulation. In this unique arrangement, upper and lower body systemic blood flow (Q_s), oxygen delivery, and tissue oxygenation are related in a complex manner that does not necessarily lend itself to an intuitive understanding of circulatory efficiency and balance.

Article p 1243

The novel and important contribution of the article by Diller et al is their distillation of this complex relationship into a simple and clear concept. Prior models of functionally univentricular circulations, which typically have focused on the parallel pulmonary:systemic circulatory configuration characteristic of a first-stage palliation (including work by some of the authors of the Diller . . . [Full Text of this Article]