This can be an insult, an expression of pity/sympathy, or even a compliment, depending on the context. As an insult, it can mean a variety of things, ranging from "what an idiot" to "f*** you". In a more sympathetic way, it can mean something to the effect of "I feel bad for you/so-and-so" or "what a shame". As a compliment, it can actually mean "what a sweetheart" or "how cute/sweet". In that sense, it's typically referring to someone's innocence or as a term of endearment.
Examples of "bless your/his/her/their (little) heart(s)" in typical conversation:

Insult (what an idiot):
"His boss told him if he made another careless mistake when filing the data reports again, he'd fire him on the spot. Bless his heart."

Insult (f*** you):
"Hey baby, you've got to be the sexiest little thing here. How about you and I head back to my place and throw our own private party?"
"Bless your little heart. Thanks, but I think I'll pass."

Pity/Sympathy (I feel bad for you/so-and-so):
"Bless her heart, she worked so hard to bake a nice cake for her mom's birthday. But she tripped while carrying it and it was ruined when it fell on the ground."

Pity/Sympathy (what a shame):
"He could have been top of his class, if he hadn't started started skipping class to hang out with those troublemakers. Bless his heart."

Compliment (what a sweetheart):
"I don't know how she finds the time to raise those kids, clean her house, work as a part time substitute teacher, volunteer for church events, and still host occasional social gatherings in her home. Bless her heart, she's a saint!"

Compliment (how cute/sweet):
"Look, mommy! We made macaroni art at school today! Do you like it? I made it just for you."
"Bless your heart, you're so thoughtful. I love it! We'll put this on the fridge for everyone to see!"
by TygraSol February 03, 2018
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Deep in my heart, there's a fire, a burnin' heart
Deep in my heart, there's desire for a start
I'm dying in emotion
It's my world in fantasy
I'm livin' in my, livin' in my dreams
You're my heart, you're my soul
I keep it shining everywhere I go
You're my heart, you're my soul
I'll be holding you forever
Stay with you together
You're my heart, you're my soul
Yeah, a feelin' that our love will grow
You're my heart, you're my soul
That is the only thing I really know
Let's close the door and believe my burnin' heart
Feeling all right come on, open up your heart
I'll keep the candles burning
Let your body melt in mine
I'm livin' in my, livin' in my dreams
You’re My Heart, You’re My Soul
I keep it shining everywhere I go
You’re My Heart, You’re My Soul
I'll be holding you forever
Stay with you together
You're my heart, you're my soul
Yeah, a feelin' that our love will grow
You're my heart, you're my soul
That is the only thing I really know
You're my heart, you're my soul
Yeah, a feelin' that our love will grow
You're my heart, you're my soul
That is the only thing I really know
You're my heart, you're my soul
Yeah, a feelin' that our love will grow
by Death Menace February 08, 2023
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can you hear my heart beat

THE YURI ON ICE INTRO SENT DOWN BYE THE GODS 😩😩😩😩
Intro: can you hear my heart beat?

Me: YES YES I CANN
by Affixis May 04, 2021
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An ad that I see all the fucking time on Urban Dictionary.
4 Signs You're About to Die of a Heart Attack. *Insert image of foot.*
by Lorf_TheArtist June 24, 2019
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A special burger with poblano pepper
"Hey Bob, what's the burger of the day?" "It's the Sgt Poblano's Lonely Hearts Club Band Burger, you should try it!"
by America Lover 🇺🇸 November 17, 2018
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Irish Heart Attack

A mixed drink involving equal parts of Five-Hour Energy and Jameson Irish Whiskey
Dude: "I think that guys dead"
Other Dude: "Yeah he was doing the Irish Heart Attacks"
by Charles Lee 69 April 28, 2013
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