Heart attack

A Heart attack was a condition affecting certain individuals of near-human species.

The Doctor, who, being Gallifreyan, had a binary vascular system, once had a "one-sided" heart attack. (NA: So Vile a Sin)

Geraint Cooper suffered from a series of heart attacks. (TW: The New World, The Categories of Life)

Real world
Several Doctor Who contributors have suffered from heart attacks:
 * Patrick Troughton had three major heart attacks, in 1978, 1984 and 1986 respectively, he died from the last one.
 * Ian Marter died of a heart attack in 1986.
 * Jon Pertwee died of a heart attack in 1996.