Vignati C, Cattadori G

Ann Am Thorac Soc. 2017 Apr 25. doi: 10.1513/AnnalsATS.201611-852FR. [Epub ahead
of print]

Cardiac output is a key parameter in the assessment of cardiac function, and its
measurement is fundamental to the diagnosis, treatment, and prognostic evaluation
of all heart diseases. Until recently, cardiac output determination during
exercise had been only possible through invasive methods, which were not
practical in the clinical setting. Since oxygen uptake (V.O2) is cardiac output
times arteriovenous content difference [C(a-v)O2)], evaluation of cardiac output
is usually included its measurement. Because of the difficulty of directly
measuring peak exercise cardiac output, indirect surrogate parameters have been
proposed, but with only modest clinical usefulness. Direct measurement of cardiac
output can now be made by several noninvasive measurements, such as rebreathing
inert gases, impedance cardiology, thoracic bioreactance, estimated continuous
cardiac output (EsCCO) technology, and transthoracic echocardiography coupled to
cardiopulmonary exercise testing allow more definitive results and better
understanding of the underlying physiopathology.