I think it requires a fair amount of force to choke off one's supply of oxygen enough to cause cardiac arrest. But I don't know.
Why did the family wait 12 years to raise their concerns about strangulation?
Because the "husband" hid the bone scan for a decade. It was released to the Schindlers in a "document dump" per court orders.
All one has to do is cut of air supply to the wind pipe .. that does not take much effort to do and with her low potassium and lack of oxygen .. that could cause her to have a heart attack
I'm not saying that MS intended to kill her that night
But it is possible that he did get into a heated argument with her and one thing lead to another
There are some that are on record stating they did have a troubled marriage and that MS often got angry at his wife for such things as spending money
As for her family waiting 12 years .. I believe there have been questions for many many years with regard to this
But they officially filed a court request for an investigation .. which was denied by Judge Geer