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.
Because the ST segment on the ECG does not become elevated in this condition, it is called a non-ST-segment elevation myocardial infarction, or NSTEMI. When the blood clot that forms during ACS completely blocks the artery, all the heart muscle supplied by the artery begins to die. This, the most severe consequence of an ACS, is called a STEMI. In many cases, a STEMI is preceded (by hours, days or weeks) by unstable angina and/or an NSTEMI.