Results from our laboratory have shown that there is a sex-specific difference in cardiac size and mass even in healthy humans and that women have a smaller (and therefore, less distensible) heart compared with men (2, 54). It is possible that such a sex difference is exaggerated in POTS patients. This notion is supported by a recent study of Miwa and Fujita (8) showing that a considerable number of chronic fatigue syndrome patients had a small heart, as assessed by roentgenography and echocardiography. POTS is a frequent finding in patients with chronic fatigue syndrome (55). It is highly likely that the small heart contributes to the development of POTS and probably should be included in the genesis of this syndrome.
By using a cardiac MRI technique, we assessed precisely the heart size and mass in patients with POTS and found that the heart was approximately 16% smaller in these patients and more than 2 SDs smaller than the true mean for healthy sedentary controls. In the famous children's book How the Grinch Stole Christmasby Dr. Seuss (56), subsequently popularized by the movie of the same name (2000), the main character had a heart that was “two sizes too small.” We suggest, then, that a more pathophysiologic name for POTS is the “Grinch syndrome,” emphasizing that a small heart is the primary abnormality and target for therapy. A small heart coupled with reduced blood volume contributes to the small stroke volume, ultimately resulting in reflex tachycardia during orthostasis in these patients.
Hi @Strawberry -- My understanding is that many people who had COVID-10 now have POTS as part of their Long-Hauler situation. I've also been seeing reports that people just getting the COVID vaccine are ending up with POTS. There doesn't seem to be a small heart syndrome involved in either one of these situations.