https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.061025
Discussion
That is also not the full article and does not explain about the proposed underlying cause. 🙃
I think it's pretty clear findings without reviewing the supplemental materials;
"A notable finding was that markedly elevated levels of full-length spike protein (33.9±22.4 pg/mL), unbound by antibodies, were detected in the plasma of individuals with postvaccine myocarditis, whereas no free spike was detected in asymptomatic vaccinated control subjects (unpaired t test; P<0.0001)."
You have to subscribe or pay to view. It's a apeer-reviewed journal.