Erythema multiforme (EM) is a skin reaction that comes from an infection or another trigger. EM is a type of allergic reaction. In most cases, it occurs in response to an infection. In rare cases, it is caused by certain medicines or body-wide (systemic) illness. Infections that may lead to EM include:
1 Heart attack. A heart attack can damage the area of the heart muscle that supports the mitral valve, affecting the function of the valve. If the damage is extensive enough, a heart attack can cause sudden and severe mitral valve regurgitation.  Abnormality of the heart muscle (cardiomyopathy).
The heart valve is unable to fully open and blood flow through the valve is restricted. Regurgitation or backflow occurs as a result of a prolapsed valve. Also known as a leaky valve, a prolapse occurs when the valve bulges back into a heart chamber during a heartbeat. A prolapse mainly affects the mitral valve.