A coronary occlusion is the partial or complete obstruction of blood flow in a coronary artery. This condition may cause a heart attack. In some patients coronary occlusion causes only mild pain, tightness or vague discomfort which may be ignored: the myocardium is however damaged.According to the Nicholas and Alexandra book, Tsar Nicholas II of Russia suffered a coronary occlusion right before he was toppled from his throne during the Russian Revolution in 1917.