My sister in law died of an unknown heart problem.
Someone mentioned that she had an anurism or something similar.She just dropped to the floor and died.
I'm so sorry fo your loss. I hope this helps--
"Lev's disease (or Lenegre-Lev syndrome) is an acquired complete heart block due to idiopathic fibrosis and calcification of the electrical conduction system of the heart. Lev's disease is most commonly seen in the elderly, and is often described as senile degeneration of the conduction system."