While preparing for a recent grand rounds lecture, I uncovered something rather interesting: The fact that the RV can enlarge during cardiac arrest independently of the presence of a pulmonary embolism. It turns out that the data showing RV enlargement as a marker of a pulmonary embolism is actually mostly extrapolated from alive patients (in which it has been shown to be a pretty good marker of submassive and massive PE).  There is very minimal data on RV enlargement in arrest in humans, but there are some animal studies that suggest that the RV enlarges in many causes of arrest, including hypoxia and arrhythmias.  Check out the podcast, and the summary of the literature on the PDF below: