Mitral Valve: Description and Function

By Ryan Johnasen

The Mitral Valve is also known as the Bicuspid Valve or Left Atrioventricular Valve if you are seriously into tongue-twisting - it is one of the four main valves of the heart. It is shaped like a bishop's miter (headgear) which is where the name "mitral" comes from, and is a double flapped valve which is situated between the left atrium and left ventricle. To picture this in your mind, think of two sets of paired chambers - they sit on top of each other, the upper, larger chambers are the atria (or atrium if singular) and the smaller, lower ones are the ventricles.

The mitral valve connects the left atrium (left upper chamber) to the left ventricle (left lower chamber).

Along with another valve, the Tricuspid Valve, they control the flow of blood through the heart between the atria and ventricles.

The upper chambers or atria have the job of collecting the blood as it flows into the heart from the veins in the body. Once collected, it must contract in order to force the blood into the smaller ventricles which in turn must contract to force the blood out of the heart and around the body again. The mitral valve acts to prevent the blood from flowing back into the left atrium from the left ventricle and in order to do this, it has two "leaves" which close after the left atrium has contracted, forcing blood into the left ventricle and then open once more when the left atrium is ready to contract and force blood back into the empty left ventricle.

The sound of your heartbeat will have the signature, "du-dum" sound which you may hear on a monitor or know from the television medical series and movies. The initial beat is created by the mitral valve and the tricuspid valve as they finish forcing the blood into the two lower ventricles. The louder, second beat sound is created by the action of the two lower ventricles expelling the blood from the heart as it begins its journey around the body once more.

Issues arise with the mitral valve if it fails to properly seal the opening between the left atrium and left ventricle which leads to backflow of blood from the ventricle into the atrium. This leads to a loss in blood pressure and inefficient circulation of blood around the body. The valve may leak because of inherent weakness in the two leaves which close the opening in between contractions. Another condition may occur where the structures which support the valve itself become diseased or weakened so the valve does not open properly and obstructs the flow of blood into the ventricle. Mitral valve surgery is the procedure used to identify what the root cause is of medical problem associated with it, as well as the remedy to repair the condition.

Symptoms of mitral valve disease include waking up from sleep short of breath or coughing, shortening of breath when you are lying down, exerting yourself or are emotionally distressed, feeling excessively tired, dizziness, swollen ankles or feet, experiencing a fast or irregular heartbeat or a fluttering feeling in your chest. - 30540

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