Scientists also found a "crucial" variant known to cause hypertrophic cardiomyopathy - a heart muscle disease that causes the thickening of the heart and weakening of the heart muscle.
Presley displayed many of the symptoms of this disease, including an irregular heartbeat, fatigue, fainting and high blood pressure.
The star was found dead in 1977 at 42 slumped in a bathroom at Graceland, his mansion in Memphis, Tennessee.
Producers said although it was officially known that Presley died of heart failure, the cause of his heart failure was still subject to speculation and had fuelled a "melting pot" of conspiracy theories.
Kingsmore, director of the Centre for Paediatric Genomic Medicine at the Children's Mercy Hospital in Kansas City, described the results as "a smoking gun".
"There had been so much speculation about cause of death, and so much ill spoken of his lifestyle, and we had this intriguing finding that possibly Elvis had a medical illness, and all of the stuff about how he killed himself with his lifestyle might have been very unfair," Kingsmore said.
- PAA