Los Angeles, Dec 23 : Actor Ryan O'Neal's cause of death has been officially revealed, two weeks after the actor died on December 8. The 'Love Story' actor died at the age of 82, reports 'Mirror.co.uk'. His death was announced by his son Patrick O'Neal, 56, who shared the sad news in a post on Instagram. Patrick wrote: "So this is the toughest thing I've ever had to say but here we go. My dad passed away peacefully today, with his loving team by his side supporting him and loving him as he would us." At first, Ryan's cause of death was unknown, but now it has emerged that he died of congestive heart failure. Ryan's death certificate was obtained by the Blast on Friday, revealing that the congestive heart failure was a result of suffering from cardiomyopathy for years. As per 'Mirror.co.uk', when Ryan died, he was hospitalised at Providence Saint John's Health Center in Santa Monica, California. The death certificate lists no other contributing factors to Ryan's death. According to the NHS, congestive heart failure is a term that is rarely used today, with it instead referred to as just heart failure. The condition means that the heart is unable to pump blood around the body properly. "It usually happens because the heart has become too weak or stiff", according to the site. Following Ryan's death being announced by his son Patrick on social media, his daughter - whom he had worked with on several occasions - Tatum O'Neal, 60, also spoke out. Addressing his death, Tatum told People in a statement: "I feel great sorrow with my father's passing. He meant the world to me'. Tatum added that she "loved him very much" and that she knew her father felt the same about her. "I'll miss him forever and I feel very lucky that we ended on such good terms', she added. /IANS