Patrick Muldoon's cause of death has been revealed.

The Days of Our Lives star died of myocardial infarction - a heart attack - on April 19, aged 57, according to his death certificate.

Underlying causes were pulmonary embolism and hereditary coagulopathy.

A pulmonary embolism is "when a blood clot blocks a blood vessel in your lungs", according to the National Health Service (NHS).

Coagulopathy, meanwhile, "happens when there's a problem with how your blood forms clots", Cleveland Clinic states.

The death certificate also revealed Patrick - who was listed as an actor and producer - was cremated on April 28.

He is survived by partner, Miriam Rothbart, parents, Deanna and Patrick Muldoon Sr.; his sister and brother-in-law Shana Muldoon Zappa, 48, and Ahmet Zappa, 51, his niece Halo and his nephew Arrow Zappa.

On April 20, Deadline reported that the Melrose Place alum passed away "suddenly" from a heart attack the previous morning (19.04.26).

Patrick's sudden death came two days after he took to Instagram to tell fans he had landed a role producing the new movie Kockroach, starring Chris Hemsworth, 42, Channing Tatum, 46, and Taron Egerton, 36, and that the movie would be filming in Australia.

Patrick penned: "So excited to be a part of this amazing project KOCKROACH directed by Matt Ross starring Chris Hemsworth, Taron Edgerton, Zazzie Beetz And Alec Baldwin.

"Filming now in Australia @chrishemsworth @taron.egerton @zaziebeetz #tarinedgerton #chrishemsworth #mattross #producer. (sic)"

Tributes flooded in for the Saved by the Bell entertainer following news of his shock death, including from his ex-girlfriend, actress Tori Spelling, who remembered Patrick as the "kindest, most caring human".

The 52-year-old star's heartfelt Instagram tribute read: "This post took me a couple days. I wasn't ready to write because then it felt real. And, this shouldn't be real. @thepatrickmuldoon and I met on a blind date. Which thankfully wasn't a blind date at all because we were both on a tv series.

"Like every other girl in the world I crushed on his character Austin from Days of Our Lives.

"Not sure I ever disclosed that to him.

"What I met and ultimately fell in love w/ was not just a beautiful on the outside creature but the most beautiful soul.

"He was special and one of a kind. The kindest most caring human w/ raddest weird sense of humor. We got each other! Laughed a lot ! I laughed w/him and at him and he loved it. Was multi talented. Passionate about everything he did.

"And, he had a knack for making others smile + brought absolute joy to everyone that was blessed to be in his orbit. A true gift. We shared a love of Broncos, guitars, goofing off, playing tag, and Grease! Loved to belt out Grease. I was Sandy to his Danny! (sic)"

Tori also grew close to Patrick's family, including his sister, Shana and last summer she enjoyed spending time with him and his "true love", Miriam Rothbart.

Tori said: "I also fell in love w/his sister @shanazappa. Their close brother sister relationship reminded me of my brother. His parents are amazing as well.

"I loved how close their family unit was! Professionally he always showed up. And, was a true hype man 4 those he cared about. He was a huge part of my formative 20's.

"We went on to be good friends! Still laughing + always caring.

"Decades later I found him to be such a true friend/hype man when I was going thru my divorce.

"He would call and check on me and send me the worst jokes to make me laugh. He loved when I rolled my eyes. Now I miss those stupid jokes.

"I last saw him past summer. Finally met his soulmate @miriamrothbart.

"He said we would get along + I instantly got it! She was his perfect balance. He was just having his moment. His element. Found true love, acting + producing became his "jam" as he would say. Crushing it! (sic)"

But Tori regrets not arranging to have dinner with Patrick and Miriam after their meeting last year.

The 90210 cast member added: "Don't believe in regrets but regret not setting that dinner w/him + Miriam after that. Life is short. Set that dinner.

"We called each other F***face [crying laughing emoji]. That was us!

"I'm sorry to his family and the world for a beautiful light put out too soon. LoveU 4EVR F***Face (sic)"