From a CBS press release:

In a live interview on THE EARLY SHOW today, David Letterman's mother, Dorothy, told news anchor Julie Chen that Dave's father died of a heart attack when he was in his 50s and that has been on her mind and Dave's. The transcript of the interview follows. You must credit CBS News' THE EARLY SHOW.

JULIE CHEN, co-host:
Welcome back to THE EARLY SHOW. When David Letterman returned to the "Late Show" on Monday for the first time following his quintuple bypass surgery, there was no one happier in America than his mom. Dorothy Letterman became a household face when her famous son put her to work. The 78-year-old homemaker has traveled the globe, filing humorous reports for his show. She's covered two different Olympic Games and has played tour guide in London. She also reports frequently from the friendly confines of her hometown in central Indiana. Dorothy Letterman, good morning.

Ms. DOROTHY LETTERMAN (Dave's Mom): Good morning.

CHEN: Do I call you Dorothy? Or do I call you Mama Letterman? Dorothy's OK?

Ms. LETTERMAN: Dorothy's fine.

CHEN: How you doing?

Ms. LETTERMAN: I'm doing fine now that David's fine.

CHEN: I was just going to ask you, when is the last time you saw or spoke to him and how is he?

Ms. LETTERMAN: I spoke to him on Friday, a week--last Friday after he had taped his first show. And we were due to come into New York that day, but La Guardia Airport was closed down and so they didn't fly any planes from Indianapolis to New York. So...

CHEN: That's right.

Ms. LETTERMAN: �we didn't get here. So...

CHEN: You just got in...

Ms. LETTERMAN: We got in last night.

CHEN: So you haven't seen him yet?

Ms. LETTERMAN: Not yet, no.

CHEN: Now last night's show, he kind of poked a little bit of fun at you.

Ms. LETTERMAN: I know.

CHEN: And he kind of did an imitation where he made you out to be, as any mom should be, kind of overprotective. Let's take a look at that clip.

(Excerpt from "The Late Show")
DAVID LETTERMAN: People say to me a couple of things. They always say, first of all, don't overdo it.

PAUL SHAFFER: Yeah.

LETTERMAN: Like my mom, the first--'Now, David. Don't overdo it.'

SHAFFER: That's...

LETTERMAN: Like, 'What are you talking about, Mom? Handball? Is that what you're talking about?'
(End of excerpt)

CHEN: Is that a good imitation and did you really say that?

Ms. LETTERMAN: That's not a good imitation, but that's basically what I told him. I said, just take it easy. Don't do too much, too fast, because you need to get over this and get completely well, which I'm sure he is. Just--he's practically--well, he's fine.

CHEN: He looks great. We've seen him twice now this week and he looks great. But what was his reaction when you said, 'Now, Dave'--I can't do it because that wasn't a good imitation. Does he listen to his mom?

Ms. LETTERMAN: Not really. He's...

CHEN: Did he ever listen to mom?

Ms. LETTERMAN: Well, I suppose on occasion he did. But, it's...

CHEN: You know, on the first night that he came back, I think a lot of us were surprised at how choked up he got when he introduced the medical staff that helped him out. Let's take a look at that clip.

(Excerpt from "The Late Show")
LETTERMAN: So it was five weeks ago today that these men and womenright here saved my life and... Canceled the gig, right?
(End of excerpt)

CHEN: I was surprised. I think most of America was surprised. Were you surprised that your own son got choked up?

Ms. LETTERMAN: No.

CHEN: Why?

Ms. LETTERMAN: That's the David I know. I mean, the one that America sees on TV, the "funny man," quote unquote, is--but basically, he is a very sentimental young man. And he feels very deeply. And, of course, the first thing he told me when I talked to him after the surgery, 'They saved my life, Mom.' And so he is...

CHEN: Was he tearful then?

Ms. LETTERMAN: Yes, he was. He was very, very happy that this had been done, because I'm thinking this had been on his mind for awhile, since his father died of a heart attack. And in his 50s and when David turned 50, I think maybe -- he never said, but I think maybe it was on his mind. And I'm sure it was, as it was on mine. And so I'm delighted that things have gone so well, and that he is recuperating beautifully, and he's back doing what he loves to do.

CHEN: We wish him the best...

THE EARLY SHOW is broadcast weekdays (7:00 - 9:00 AM, ET/PT) on the CBS Television Network.