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An atrial septal defect (ASD) is a hole in the wall between the two upper chambers of your heart (atria). The condition is present from birth (congenital). Small atrial septal defects may close on their own during infancy or early childhood. Large and long-standing atrial septal defects can damage your heart and lungs. Small defects Read more…

In atrial flutter, your heart’s upper chambers (atria) beat too quickly. This causes the heart to beat in a fast, regular rhythm. Atrial flutter is a type of heart rhythm disorder (arrhythmia) caused by problems in your heart’s electrical system. Atrial flutter is similar to atrial fibrillation, a common heart rhythm disorder. However, the rhythm Read more…

Atrial fibrillation is an irregular and often rapid heart rate that can increase your risk of stroke, heart failure and other heart-related complications. During atrial fibrillation, the heart’s two upper chambers (the atria) beat chaotically and irregularly — out of coordination with the two lower chambers (the ventricles) of the heart. Atrial fibrillation symptoms often Read more…

Atopic dermatitis (eczema) is a condition that makes your skin red and itchy. It’s common in children but can occur at any age. Atopic dermatitis is long lasting (chronic) and tends to flare periodically and then subside. It may be accompanied by asthma or hay fever. No cure has been found for atopic dermatitis. But Read more…

Athlete’s foot (tinea pedis) is a fungal infection that usually begins between the toes. It occurs most commonly in people whose feet have become very sweaty while confined within tight-fitting shoes. Signs and symptoms of athlete’s foot include a scaly rash that usually causes itching, stinging and burning. Athlete’s foot is contagious and can be Read more…

Atelectasis (at-uh-LEK-tuh-sis) — a complete or partial collapse of a lung or lobe of a lung — develops when the tiny air sacs (alveoli) within the lung become deflated. It’s a breathing (respiratory) complication after surgery. Atelectasis is also a possible complication of other respiratory problems, including cystic fibrosis, inhaled foreign objects, lung tumors, fluid Read more…

Ataxia describes a lack of muscle control during voluntary movements, such as walking or picking up objects. A sign of an underlying condition, ataxia can affect movement, speech, eye movement and swallowing. Persistent ataxia usually results from damage to your cerebellum — the part of your brain that controls muscle coordination. Many conditions can cause Read more…

Astigmatism (uh-STIG-muh-tiz-um) is a common, mild and generally easily treatable imperfection in the curvature of your eye. The condition can cause blurred vision. Astigmatism occurs when the front surface of your eye (cornea) or the lens, inside your eye, has a slightly different surface curvature in one direction from the other. Instead of being even Read more…