The Young and the Restless actor Kristoff St. John died from heart disease, and alcohol was a contributing factor, the Los Angeles County coroner’s office said Tuesday. The coroner’s report listed the star’s official cause of death as "hypertrophic heart disease" — a condition that thickens the heart muscle and can make it harder for the heart to pump blood, according to the Mayo Clinic. The manner of death was determined to be an accident. St.