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.
ST-segment is a portion of ECG; its elevation indicates full thickness injury of heart muscle. Absence of ST-segment elevation in NSTEMI is understood to involve less than full thickness (partial thickness) damage of heart muscle. Therefore, NSTEMI is less severe type of heart attack compared to STEMI (ST-segment elevation myocardial infarction) in which full thickness damage of heart muscle develops.