Close this search box.

Heart Preload Failure

This study aims to evaluate these different explanations of PLF in ME/CFS patients to determine which is active in many, if not all, ME/CFS patients.

  • Wenzhong Xiao, PhD
  • David Systrom, MD

Two forms of heart failure identified in ME/CFS patients: preload failure and poor oxygen extraction. Preload failure consistently shows a reduced max VO2 (~80%) (VO2 max: maximum amount of oxygen your body can utilize during exercise) along with a reduced right atrial pressure (RAP). The poor oxygen extraction patients routinely also show a reduced max VO2 (~80%) and unexpectedly high pO2 in the mixed venous blood (pav O2). The first form suggests an autonomic dysregulation and the second form may suggest either mitochondrial oxidation or peripheral shunting dysfunction.


Invasive Cardiopulmonary Exercise Testing (iCPET) on Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME / CFS) patients shows a characteristic pattern of “preload failure” (PLF) that could be associated with postural orthostatic tachycardia syndrome (POTS) and/or post-exertion malaise (PEM).

The 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.


  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.
Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME / CFS) Post Treatment Lyme Disease Syndrome (PTLDS), Fibromyalgia Leading Research. Delivering Hope.Open Medicine Foundation®

What are the advantages of giving from your Donor Advised Fund (DAF)?

  • Your gifts to your donor advised fund entitle you to an immediate income tax deduction at the time of contribution.
  • You avoid capital gains tax on appreciated assets you place in your donor advised fund.
  • Your fund’s investment gains accumulate tax free.
  • Funds are distributed to Open Medicine Foundation in your name and immediately put to use to support our worldwide research efforts.

How do I make a donation through my DAF?

Just click on the DAF widget below. It is simple and convenient to find your fund among the over 900 funds in our system.

Still can’t find your fund? 

  • Request a grant distribution through your Donor Advised Fund sponsor
  • Be sure to use OMF’s EIN #26-4712664
  • You can also designate OMF as a beneficiary for your Donor Advised Fund
  • Questions? Give us a call at 650-242-8669