https://www.npr.org/2021/03/14/97282...ce=twitter.com
Long interesting article at link
Her heart, as strong as it had been, was spent. Her liver, pancreas and kidneys stopped functioning due to the lack of circulation. The heart's electrical system became chaotic and developed irregular rhythms called ventricular fibrillation.
"Her heart had stretched out to an extent that was not compatible with life," Choo said. Instead of pumping, the heart merely quivered, and then finally stopped.