They keep saying the woman in the vegetative state suffered "heart failure", and that's what put her in that state.
But heart failure is almost always a chronic condition that runs for weeks, months, or even many years with treatment. It usually stems from long-term high blood pressure that puts a load on the heart, and over time the becomes enlarged (dilated). And loses its pumping efficiency. As it progresses the person retains fluid in their extremities and lungs. They also mention an arrhythmia and seem to use the two diagnoses interchangeably. But it's more likely she had a serious injury that led to poor perfusion of the brain and brain death/damage.