Last reviewed 01/2018

Unstable angina is caused by intermittent reduction in oxygen supply to the myocardium, rather than an increase in oxygen demand (1). It is caused by the abrupt, total or sub-total, transient and typically recurrent obstruction of a coronary artery.

  • unstable angina is caused by erosion or rupture of the cap of an atheromatous plaque with superimposition of a platelet-rich thrombus
  • spontaneous fragmentation or lysis of the thrombus, allows resolution of myocardial ischaemia. Howver distal embolism may result in myocardial necrosis - this is reflected in the release of cytosolic proteins (e.g. troponins T and I)
  • a fully developed myocardial infarction with Q waves may occur if there is persistence of an occlusive thrombus


  • British Heart Foundation, Factfile 6/2000