Yes, I am saying in many cases we don't know cause of death. In most of the US we do a crap job of discovering cause of death in many cases. When you dig into the numbers specific coroners often have different old guy died in sleep dumping grounds. 'Hart disease' often ends up as a grab bag for any number of quiet killers such as: http://en.wikipedia.org/wiki/Pulmonary_Embolism.

PS: Perhaps the most humorous being http://en.wikipedia.org/wiki/Fan_death, but the sadist and most blunt is probably: http://en.wikipedia.org/wiki/Sudden_infant_death_syndrome which is literally 'death without obvious cause'.