The cause of death of singer Natalie Cole has been revealed.

According to her family, Cole died of complications from idiopathic pulmonary arterial hypertension (IPAH).

In a statement, Cole’s family said that she was diagnosed with IPAH shortly after her successful kidney transplant in 2009.

“This is a very serious and progressive disorder in which the small blood vessels of the lungs are markedly narrowed or obstructed … She responded well to PAH-specific agents over many years, during which she performed many concerts world-wide, but eventually succumbed to intractable right heart failure, an outcome that unfortunately commonly occurs in this progressive disorder, despite modern therapies,” said Cole’s family in the statement.

Cole, the daughter of Nat King Cole, died at the age of 65 last week.

Singer Natalie Cole dies at 65 https://t.co/PWGPoBBW5i pic.twitter.com/LbAhzGhNU2

— Variety (@Variety) January 2, 2016

“It is with heavy hearts that we bring to you all the news of our Mother and sister’s passing,” her family said at the time. “Natalie fought a fierce, courageous battle, dying how she lived…with dignity, strength and honor. Our beloved Mother and sister will be greatly missed and remain UNFORGETTABLE in our hearts forever.”