It doesn’t say she did. Cardiopulmonary arrest is the catch all phrase for “ heart and lungs stopped. Not the same as Myocardial Infarction. She could have died from hemorrhage , PE, or sepsis, all common post op causes of death or arrhythmia or any number of other causes.
Addendum. The article is somewhat confusing as to timing. If she died during the procedure or immediate post op period I’d say bleeding or anesthetic complication climbs to the top of the list for immediate cause of death, although an amniotic embolism and arrhythmia are lower.