Chaos in the cardiovascular system: an update

Rhythmic changes of blood pressure, heart rate, and other cardiovascular measures have drawn the attention of several investigators, since these oscillations can shed light onto the activity of the underlying control network. The overwhelming proportion of circulatory variations, however, are not linear, i.e., they do not consist of perfectly rhythmic components. Thus, these fluctuations are more adequately analysed by non-linear techniques, most of which are adopted from chaos theory. A spotlight issue of 'Cardiovascular Research' (Vol. 31, 1996), focused on chaos in the cardiovascular system. This current review outlines today's understanding of this field by presenting the major discoveries and developments which have taken place since then.