Orthostatic intolerance with small heart and/or disequilibrium in patients with myalgic encephalomyelitis/chronic fatigue syndrome: clinical update and paradigm shift

Description

Miwa gave in 2026 a clinical update on orthostatic intolerance in myalgic encephalomyelitis and chronic fatigue syndrome, where patients cannot stay upright without severe symptoms. Standing shifts about 800 millilitres of blood toward the pelvis and legs, and healthy bodies answer with faster heart rate and tighter vessels. Most patients with this illness show the intolerance, and it is the main limit on their daily function.

Miwa reports that many patients have a small left ventricle, the heart's main pumping chamber, with low output to match. The hormone systems that guard blood volume are also turned down in these patients. Newer work adds postural instability, a balance problem possibly tied to the inner ear system, alongside the blood flow story. Miwa frames this as a shift in how the syndrome's upright symptoms should be understood and assessed in clinic.

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Source: https://europepmc.org/article/MED/PMC13463185