Mitral Regurgitation

Learn the basics of mitral regurgitation.
March 3, 2021


Mitral regurgitation (MR) is a condition in which the mitral valve does not close properly, allowing blood to flow backward from the left ventricle into the left atrium during systole.  MR is predominantly caused by degenerative disease in developed countries and rheumatic fever in developing countries. MR occurs due to an abnormality in the valve apparatus involving  the leaflets, chordae tendineae, papillary muscles or the annulus. It is the most common valvular heart disease, and if severe and left untreated,  can cause complications such as arrhythmias and heart failure. 


In the acute phase of Mitral regurgitation (MR), the stroke volume of the left ventricle is increased to support the volume overload from the blood that is regurgitated into the left atrium. The regurgitant volume causes a pressure overload which inhibits the drainage of the blood from the lungs, leading to pulmonary congestion. Over time, the increased blood volume within the left atrium and increased preload to the left ventricle eventually causes the heart to undergo remodeling, leading to dilatation and decreased contractility, resulting in a reduced ejection fraction.


A high-pitched, holosystolic murmur heard best at the apex, radiating to the base with posterior prolapse and to the axilla with anterior prolapse. The recommended patient position is supine. A soft S1 and apical S3 is also commonly heard. 


There are no specific ECG changes for Mitral regurgitation (MR). In chronic MR, broadening of the P waves may be seen on the ECG due to left atrial enlargement.