Circulatory dysfunction in ME/CFS

Prof David Systrom presented findings from an invasive cardiopulmonary exercise test (iCPET) in ME/CFS and Long COVID. The test was originally developed to detect early signs of heart failure. The test is invasive due to measurements being taken via a central venous catheter during a physical exercise test. In ME/CFS, evidence was found of reduced preload, in which venous return to the left ventricle is reduced, resulting in too little blood being supplied to the heart and a reduced pumping capacity. As a result, the body is not supplied with blood efficiently. A subgroup of test subjects showed impaired oxygen uptake, which also contributes to reduced tissue oxygenation. In addition, two-thirds of ME/CFS patients exhibited small fiber neuropathy (SFN), which can also limit oxygen supply and blood flow to tissues and lead to a functional left-to-right shunt. A clinical study is currently investigating the extent to which the reduced preload can be reduced by pyridostigmine (sold under the brand name Mestinon or Kalymin) – a cholinesterase inhibitor that increases the availability of the neurotransmitter acetylcholine and can thus potentially reduce muscle weakness and fatigue.