The definition of a heart dog for me, is Bella.
Bella's my heart dog, she's a challenge, she's my baby, she's a lover, she's a fighter. She's everything I didn't want in a dog, and everything I did. She may not be the best behaved, but she's my heart dog, and I assume it's because we've gone through so much together.
I love Zoey, and I love Psyche, and I feel a connection with them, I do, but not as strong as Bella. Bella acts like she knows what's going on in my head. I've had a bad day, she offers cuddles, I need a smile, she offers licks, I need a hug, she lays there and lets me hug her.
I can't imagine life without this dog.