Cardiac dysfunction and orthostatic intolerance in patients with myalgic encephalomyelitis and a small left ventricle.
Miwa, Kunihisa·Heart and vessels·2015
This study looked at heart function in 40 ME/CFS patients compared to 40 healthy people. Researchers found that ME/CFS patients frequently had smaller hearts and difficulty standing up without dizziness or other symptoms (orthostatic intolerance). The smaller heart size appeared to pump less blood with each beat, which may explain why patients struggle with upright posture and fatigue.