Yin-Yang: the long-term behavior of the cardiovascular system

Introduction: The aim of this paper is threefold. Firstly, to show that Hippocratic medicine (HM) and Traditional Chinese medicine (TCM) can be easily understood in terms of the cardiovascular system (CVS) function and that, in fact, they help to understand it. Indeed, in fact both HM and TCM presume that Pcap = Pms where Pcap is mean capillary pressure and Pms mean systemic pressure as defined by Guyton in his model of the systemic circulation. This implies that the pressure-diuresis mechanism does not have an infinite gain and, therefore, that its effect on blood volume is overruled in the long term by that of another factor. Secondly, to show that seemingly salt intake is this factor that overrules pressure-diuresis and determines blood volume in the long term. Thirdly, to show, by means of an enhanced version of Guyton’s model that incorporates this vital piece of information (i.e., Pcap = Pms), how numerous pathologies are related to certain extreme hemodynamic conditions and, in particular, presumably, to an inadequate salt intake. Methods & Results: Guyton’s model of the systemic circulation is used to create a simulation with a spreadsheet describing the long-term behavior of the CVS. Conclusions: Hemodynamics is fundamental. i) Two types of mild primary arterial hypertension exist, the volumetric or damp type described by Guyton and a dry type that remains unrecognized as such. ii) Severe arterial hypertension seemingly results from the nervous system being compelled to increase vascular tone in both arteries and veins to compensate for failing diuresis and thereby reduce blood volume by shifting plasma into the interstitial compartment, thus protecting arteries from an excessive blood volume that endangers them. iii) Fibromyalgia corresponds to venous hypertension. iv) Many cases of autoimmune disease are due to excessive dryness—i.e., a too low Pcap. v) Chronic fatigue corresponds to low blood rate of flow and dryness. vi) Complications in COVID-19 and long COVID are frequently attributable to dryness. vii) Numerous pathologies are presumably related to inappropriate salt intake. viii) HM and TCM diagnosis are based on CVS function. ix) Two factors govern the CVS as concerning functional troubles: preload and contractility. TCM provides a richer, more vivid, practical and complete description of them through the concepts of Yin and Yang. x) The heart becomes more easily exhausted in women than in men: that is why Yang is masculine and Yin is feminine. xi) Clinical studies should confirm these conclusions.