Chief of Surgery Richard Webber (James Pickens, Jr.) was not a particularly faithful husband, having had an intense past affair with Meredith's mother during their residency, and later having another one with Catherine Fox (Debbie Allen). But despite such infidelities, he still loved his wife Adele (Loretta Devine), who stuck by his side. When she began exhibiting symptoms of Alzheimer's in Season 7, Richard was initially in denial of her diagnosis, but was eventually forced to admit his wife's rapidly-accelerating condition.
Adele deteriorated over time, until he realized she was no longer safe at home alone and needed the care of a dedicated mental care facility. After moving her into one, Richard continued to visit, but her condition worsened until she could no longer remember him at all, and Richard realized his visits were only upsetting her.
As Adele was in the facility, he began seeing Catherine, but returned to her side when Adele was admitted to the ER at the beginning of Season 9. Despite Meredith and Miranda performing a successful surgery, Adele's heart couldn't take it, and she died of a heart attack later that day.
Her death resulted from the long, agonizing decline of an endlessly frustrating disease, made even worse by the difficulties in Richard and Adele's marriage, making things so hard on them both before Alzheimer's even became part of the equation.
