A Glossary of Heart Disease Terms
Mitral Insufficiency (mitral regurgitation): A condition where blood in the left ventricle leaks back through the mitral valve into the left atrium and can back up into the lungs. The mitral valve normally opens to allow blood to flow into the left ventricle and then closes, preventing blood from backing up into the atrium during the ventricle's contraction.
Mitral Stenosis: A condition where the mitral valve becomes narrowed (stenotic), preventing the easy flow of blood from the left atrium into the left ventricle.
Mitral Valve: The valve that lies between the left atrium and left ventricle (main pumping chamber of the heart). This valve allows blood to flow from the left atrium into the left ventricle and then prevents the back flow of blood into the left atrium during ventricular contraction.
Morbidity Rate: The percentage of people who have complications from a medical condition or after a procedure or treatment.
Mortality Rate: The percentage of deaths associated with a disease or medical treatment.
Multigated Acquisition Scan (MUGA scan): A nuclear scan that evaluates the pumping function of the ventricles by determining the heart's ejection fraction.
Murmur: Turbulent blood flow across a heart valve that creates a "swishing" sound heard by a stethoscope.
Myocardial Biopsy (Cardiac biopsy): An invasive procedure to obtain a small piece of heart muscle tissue that is sent to a laboratory for analysis.
Myocardial Infarction (Heart attack): See heart attack (above).
Myocarditis: Inflammation of the myocardium (heart muscle).
Myocardium: Heart muscle.
Myomectomy: A surgical procedure to remove abnormally thickened heart muscle. Myomectomy is used to treat people with idiopathic hypertrophic subaortic stenosis (IHSS) or HOCM, thereby relieving the obstruction to blood flow in the left ventricle during contraction.
Nitroglycerin: A medication used to relax and dilate the blood vessels (vasodilator), improving blood flow. Nitroglycerin works very quickly and is the most common vasodilator used to treat angina.
Non-Q-Wave MI (NSTEMI or non-ST-elevation MI): A heart attack that does not cause changes known as "Q-waves" on the electrocardiogram (ECG). However, other changes on the ECG are often seen. In addition, chemical markers in the blood indicate that damage has occurred to the heart muscle. In non-Q-wave MI, a clot may block the coronary artery for a period of time, and then break up by itself or collateral circulation may help to restore blood flow. The size of damage is fairly small; therefore, overall function of the heart is usually maintained.