I recently realized what the "bad heart" my father's family suffered from meant.
I'd worried I'd inherit their cardiology issues - my N Grandma, SG aunt, and NF all had "bad hearts."
Except that my N Grandma spent several decades trying to fill the black hole in her heart with junk food, alcohol, and cigarettes and died of a fourth heart attack, after she had used her "bad heart" to manipulate her husband and children into quivering obedience.
Except that my aunt never had heart issues - when she claimed she did, she was just blind drunk. When she claimed she couldn't have kids because of her "bad heart," she just meant that her evil mother had forbidden her to have any other children to care for but her and that she had made her abort the child she'd conceived with the man she loved but wasn't allowed to marry. She died of cirrhosis of the liver after several decades of trying to fill the black hole in her heart with alcohol and cigarettes on an empty stomach.
Except that my NF just suffers from manageable high blood pressure after several decades of trying to fill the black hole in his heart with junk food, alcohol, and cigarettes. He's actually surprisingly healthy for his age, activity level, and diet.
The bad heart transmitted in my family is a metaphor. It's the heartlessness of the parents and the broken hearts of the children. None acknowledged, none made conscious, none properly mourned.