What was the cause of death of John III Sobieski, the King of Poland and Grand Duke of Lithuania?

John III Sobieski (17 August 1629 – 17 June 1696), was King of Poland and Grand Duke of Lithuania from 1674 until his death, and one of the most notable monarchs of the Polish–Lithuanian Commonwealth. He was an able military commander, most famous for his victory over the Turks at the 1683 Battle of Vienna. After his victories over them, the Ottomans called him the "Lion of Lechistan"; and the Pope hailed him as the savior of Christendom. King John III Sobieski died in Wilanów, Poland on 17 June 1696 from a sudden heart attack.