Possible Role of Fibrinaloid Microclots in Postural Orthostatic Tachycardia Syndrome (POTS): Focus on Long COVID.

Postural orthostatic tachycardia syndrome (POTS) is a common accompaniment of a variety of chronic, inflammatory diseases, including long COVID, as are small, insoluble, 'fibrinaloid' microclots. We here develop the argument, with accompanying evidence, that fibrinaloid microclots, through their ability to block the flow of blood through microcapillaries and thus cause tissue hypoxia, are not simply correlated with but in fact, by preceding it, may be a chief intermediary cause of POTS, in which tachycardia is simply the body's exaggerated 'physiological' response to hypoxia. Similar reasoning accounts for the symptoms bundled under the term 'fatigue'. Amyloids are known to be membrane disruptors, and when their targets are nerve membranes, this can explain neurotoxicity and hence the autonomic nervous system dysfunction that contributes to POTS. Taken together as a system view, we indicate that fibrinaloid microclots can serve to link POTS and fatigue in long COVID in a manner that is at once both mechanistic and explanatory. This has clear implications for the treatment of such diseases.

A comparison of the diagnostic yield of rigid and semirigid thoracoscopes.

Medical thoracoscopy has an important place in the diagnosis and management of pleural disease. However, the application of this procedure is limited in the United Kingdom. This may be partly because respiratory physicians remain unfamiliar with standard rigid thoracoscopy instruments. However, the semirigid variant, popular in Europe and Japan, is similar in design to the commonly used flexible bronchoscope. The larger biopsy size obtained with the conventional rigid thoracoscope has been quoted as a reason for its superiority. To compare the histologic yield of the 2 instruments, the current authors studied a series of 66 patients with unilateral exudative pleural effusions. Twenty-seven rigid and 39 semirigid thoracoscopy procedures were included. Thoracoscopic pleural biopsy achieved a positive diagnosis in 26 of 27 patients in the rigid thoracoscopy group (96.3%) and 36 of 39 patients in the semirigid group (92.3%). Statistically, this difference was not significant (95% confidence intervals, -0.11 to 0.17). Our study demonstrates that the semirigid thoracoscope achieves a diagnostic yield similar to that of the conventional rigid instrument despite the smaller biopsy size. Both instruments remain valuable in the evaluation and management of pleural disease.