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 UK National Health Service.
Coagulopathy "happens when there's a problem with how your blood forms clots", Cleveland Clinic says.
The death certificate also revealed Muldoon - 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 died suddenly from a heart attack the previous morning.
Muldoon'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, Channing Tatum and Taron Egerton, and that the movie would be filmed in Australia.Â
Tributes flooded in for the Saved by the Bell entertainer following news of his shock death, including from his ex-girlfriend, actor Tori Spelling, who remembered Muldoon as the "kindest, most caring human".
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