Blood leaks back into the chambers rather than flowing forward through the heart or into an artery. In the United States, backflow most often is due to prolapse. Prolapse is when the flaps of the valve flop or bulge back into an upper heart chamber during a heartbeat. Prolapse mainly affects the mitral valve.
NSTEMI is a shorthand medical term for non-ST segment elevation myocardial infarction. It is one type of myocardial infarction also called heart attack.
Both UA and NSTEMI, as well as ST elevation MI, are associated with unstable coronary lesions and plaque rupture. (See The role of the vulnerable plaque in acute coronary syndromes.) DEFINITIONS.