When Natalie Cole passed away on New Year's Eve, it was reportedly because congestive heart failure, but it had not yet been confirmed, as HNGN previously reported. Her family has now officially revealed her cause of death.

The 65-year-old r&b singer and daughter of Nat King Cole did in fact die as a result of heart failure, which was brought on by idiopathic pulmonary arterial hypertension (IPAH), her family told ABC News on Thursday. After undergoing a successful kidney transplant back in 2009 due to drug problems and her hepatitis C diagnosis, she was diagnosed with IPAH.

"This is a very serious and progressive disorder," her family said in the statement. "[Cole] responded well to PAH-specific agents over many years, during which she performed many concerts world-wide, but eventually succumbed to intractable heart failure, an outcome that unfortunately commonly occurs in this progressive disorder, despite modern therapies."

The rare lung disease, which occurs when extra tissue forms around the pulmonary arteries and makes it difficult for blood to flow, causes shortness of breath, dizziness and sometimes chest pain, according to the Associated Press. It's unclear if IPAH was related to the "medical procedure which precipitated a lengthy hospital stay" that forced her to cancel several concerts late in 2015, and since her case was idiopathic, the exact cause of death is technically still considered unknown.