iCPET Retrospective Study of ME/CFS & Long COVID

STUDY HYPOTHESIS AND DESCRIPTION

iCPET on ME/CFS  patients shows a characteristic pattern of “preload failure” (PLF) that could be associated with postural orthostatic tachycardia syndrome (POTS) and/or post-exertional malaise (PEM).

PLF comes in 2 forms: a high flow and a low flow. The low flow form may be caused by a failure to reduce venous compliance with exercise or a pre-existing reduced overall blood volume. However, the latter is less likely because the PLF persists even when one liter of saline is given to increase the blood volume just prior to the iCPET study.  On the other hand, the high flow PLF may be caused by peripheral arterial-venous shunt effects or deficient oxygen delivery or utilization. A final explanation is that blood travels through the peripheral capillary system normally but cellular oxygen uptake and/or utilization by the mitochondria is deficient.

This project will also investigate autonomic dysfunction and the prevalence of small fiber neuropathy (SFN). SFN is a condition in which small nerve fibers are damaged, which can lead to autonomic dysfunction. Therefore, it may be more likely to be present in conditions like ME/CFS and Long COVID.

OBJECTIVES

1. Evaluate ME/CFS patients impaired with preload failure (PLF), as diagnosed by a single iCPET or by sequential iCPET, to measure large vessel vascular capacitance and blood volume, conduct additional diagnostic testing (i.e., screening for adrenal insufficiency, tilt-table testing, nerve conduction studies) and the presence of peripheral shunting and oxygen delivery.
2. Based on patient findings, implement therapeutic interventions (i.e., hydration, increased sodium intake, β-adrenergic receptor antagonists, fludrocortisone, pyridostigmine, and/or midodrine), compression stockings, and monitored exercise training.