The heart is one of the most important organ in one's body, allowing the blood to circulate and reach each and every part of it, hence the reason he's also linked to expressions about our feelings and emotions. So, in the same way, having no functional heart is a terrible thing, be it literally or metaphorically speaking. Can we truly say that a heartless person is truly alive ? I'm not really sure. And the same goes for when someone's heart is broken, his life seems to stop, nothing seems to matter anymore, that person could as well be truly dead because he's not living his life anymore.
But can we *truly* say that we die when our body dies ? While we are not physically present anymore, we still live on in the memories of our loved ones. Our actions mattered unless we're forgotten. So, can we really say that we die when our heart stop pumping ? Scientifically, yes, because our body doesn't survive the lack of blood circulation. But humanly, not really. Not until someone says our name for the last time.
On another note, does anyone know why do dogs exist ?