Graham you said your sister died from a broken heart many times. It has been proven that women do suffer from broken heart syndrome. After the quakes here, many women suffered mild heart attacks or some kind of chest complaint.
As for dying of old age, surely the body slowly breaks down with time, our faces show that with the first sign of cracks
Crumbs I must not have long to go 
Suzy W
I'm sure they do Suzy, but I meant it in a lighthearted way - lots of 'over the top' drama's from my kid sister when romances failed!

As for dying of old age, of course the body must wear out pretty much the same as an old car does but at the end of the day as said, surely you have to die of something specific even if the medic is not sure what it is there has to be a contributing factor such as heart failure?
"Lack of breath" was one of my Dad's favorite sayings!
Even though I'm like an old car myself I'll probably succumb to something like pneumonia as I have always had bad chests. As for the Mrs, I am always telling her I'm going to change her for a new model but as she's now a collectors item I think I'll hang to her for a little longer.
I will concede though occasions when either through trauma or tiredness say, some folks just give up and slip slowly away. My father-in-law lay dying of a painful cancer but would not go until his eldest and only son came to sit beside his bed, held his hand and said "Papa, I'm here", and then he just went. He died of cancer sure, but he also went of his own accord.