Preload failure

Preload failure or PLF occurs when the maximal exercise-induced cardiac output (CO) is decreased without an accompanying increase in right heart or pulmonary vascular pressures.

In cardiac physiology, preload is the end diastolic volume that stretches the right or left ventricle of the heart to its greatest dimensions under variable physiologic demand. It is defined as the length of the heart muscle just before it starts to pump and is measured clinically by the volume of blood in the left ventricle, the main pumping chamber, when it is most relaxed.

Preload can be influenced by blood volume, heart rhythm, left ventricular relaxation, and alterations in afterload.

ME/CFS
Preload failure is associated with exercise intolerance in myalgic encephalomyelitis/chronic fatigue syndrome, orthostatic hypotension, and postural orthostatic tachycardia.

Treatments
David Systrom at Brigham Women's Hospital in Boston is currently trialing the use of Mestinon in patients with preload failure.

Pyridostigmine has also been investigated.

Notable studies and publications

 * Pyridostigmine for Exercise Intolerance Treatment in Preload Failure - Meeting abstract)

Learn more

 * 2018, Advancements in ME/CFS Research, David M. Systrom, MD; Brigham and Women's Hospital | ME/CFSAlert 98 (Interview)