Pediatric Cardiology

, Volume 39, Issue 4, pp 805–809 | Cite as

The Ratio Fallacy, with Special Reference to the Cardiac Index

  • Julien I. E. Hoffman
Original Article


When comparing cardiac outputs in children of different sizes, or deciding on the normality of these outputs, we often convert the absolute output to the output per m2 body surface area—the cardiac index. For small infants, this leads to potentially large errors. The best way to evaluate these outputs is to determine their z values.


Cardiac output Body surface area Cardiac index 



I would like to thank Dr. David Teitel for his many helpful comments.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.


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© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of PediatricsUniversity of CaliforniaSan FranciscoUSA

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