Mitral annular disjunction (MAD) is a structural abnormality of the

heart The heart is a muscular organ found in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon diox ...

in the mitral annulus ring. It is generally defined as an abnormal displacement of the location of where the posterior mitral valve leaflet inserts onto the left atrial wall and the

left ventricular A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper ...

wall. This abnormal attachment allows for the mitral valve to become hypermobile and can result in ventricular arrhythmias.

History

MAD was first described in 1986 through autopsy analysis of hearts while investigating the incidence of mitral valve prolapse.

Pathophysiology

The cause of MAD is not well understood. Hypotheses of congenital, degenerative, and acquired structural abnormalities exist. However, the physical characteristics of MAD are able to be observed through a variety of cardiac imaging techniques. Normally the posterior aspect of the mitral annulus is attached to the posterior aspect of the left ventricular wall. In MAD, there is a distinct separation between the mitral annular ring and left ventricular wall. During systole, contraction of the ventricle, the mitral valve leaflet moves away from the ventricular wall and does not move as synchronously as in a heart without MAD. The degree of disjunction can range from a few millimeters to great than 10 millimeters. Mitral_Valve_RK

Histopathology_of_mitral_valve_with_myxomatous_degeneration

Diagnosis

MAD can be diagnosed with

transthoracic echocardiography An echocardiography, echocardiogram, cardiac echo or simply an echo, is an ultrasound of the heart. It is a type of medical imaging of the heart, using standard ultrasound or Doppler ultrasound. Echocardiography has become routinely used in t ...

. Additionally, it can also be diagnosed by cardiac

computed tomography A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...

and

cardiac MRI Cardiac magnetic resonance imaging (cardiac MRI), also known as cardiovascular MRI, is a magnetic resonance imaging (MRI) technology used for non-invasive assessment of the function and structure of the cardiovascular system. Conditions in which i ...

Risk factors

Mitral annular disjunction is considered a risk factor for

mitral valve prolapse Mitral valve prolapse (MVP) is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. It is the primary form of myxomatous degeneration of the valve. There ...

and

myxomatous degeneration A myxoma (New Latin from Greek 'muxa' for mucus) is a myxoid tumor of primitive connective tissue. It is most commonly found in the heart (and is the most common primary tumor of the heart in adults) but can also occur in other locations. Type ...

of the mitral valve. This is thought to be due to hypermobility of the mitral leaflet during the

cardiac cycle The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, followin ...

. There has been an observed association between MAD and cardiac arrhythmias, theorized to be caused by fibrosis of the cardiac muscle secondary to the hypermobility and myxomatous degeneration. In rare cases, this fibrosis can lead to

cardiac arrest Cardiac arrest is when the heart suddenly and unexpectedly stops beating. It is a medical emergency that, without immediate medical intervention, will result in sudden cardiac death within minutes. Cardiopulmonary resuscitation (CPR) and possib ...

References

{{Reflist Valvular heart disease