Thread by @tessfalor

#IIMEC15 Dr David Systrom

ME/CFS and Long COVID: Insights from Invasive
Cardiopulmonary Exercise Testing

Invasive CPET - exertional intolerance cause elucidated well by this test

mouthpiece measuring gases

catheters - right internal jugular (important part of the test), left wrist to look at blood pressures, measure lactate & other biomarkers

look at VO2 max, patients with ME and LC mildly impaired 70% of expected. If you stop there, might think you have simple deconditioning, but use of catheters show it's not.

Can rule out pulmonary mechanical limit to exercise. Don't see in ME or LC, unless the LC has been on… twitter.com/i/web/status/1…

can rule out left heart disease, pulmonary hypertension

patients with ME and LC (low filling pressures - preload failure in upright position, abnormal oxygen extraction)

preload failure, no intrinsic heart of lung disease

"I haven't met a patient with ME or LC who DOESN'T have preload failure"

Can't see it without catheter

Summary: in #MECFS preload failure ubiquitous, leads to low VO2 max.

like POTS in upright, have low flow and high flow groups

high flow group was interesting - have preload failure and systemic oxygen extraction

autonomic nervous system normally modifies resistance of arteries and redirects blood flow

When doesn't happen, blood goes to areas that doesn't need it

results in impaired systemic oxygen extraction

Many #pwME being Dx with small fiber neuropathy

50% of #pwME in the study had small fiber neuropathy

similar prevalence in fibromyalgia, POTS

Neurovascular dysregulation and acute exercise intolerance in ME/CFS: randomized, placebo-controlled trial of Pyridostigmine (Joseph et al., 2022)

50 women
If got active drug, VO2 went higher, cardiac output went higher

neurovascular dysregulation in ME/CFS

In #LongCOVID

Invasive CPET, 10 patients, no intrinsic heart or lung disease, compared to 10 controls

VO2 peak mildly low
cardiac output nearly normal
likely left to right shunting
impaired oxygen extraction
almost the same as ME (also likely neurovascular)

mitochondrial dysfunction

skeletal muscle biopsy of thigh, electron transport change analyzed - 10 of 11 came back with citrate synthase deficiency, thinks intrinsic mitochondrial issue

Treatments for acquired mitochondrial dysfunction different than autonomic causes of the issues

Ventilatory inefficiency = hyperventilation in #LongCovid

genesis unknown, suspicion due to signal from periphery

Exercise intolerance in LC and ME is NOT deconditioning

preload failure not related to detraining

Stickland et all, 2006 - does fitness level modulate the cardiovascular hemodynamic response to exercise?

Saltin et al., 1968 detraining study - invasive CPET didn't show oxygen extraction issue