People with a certain heart valve abnormality may be at an increased risk of developing severe heart rhythm disorders, also known as arrhythmias, according to a study on Tuesday. 

Researchers from the Karolinska Institute in Sweden showed that the valve abnormality called Mitral annular disjunction (MAD) increases the risk of ventricular arrhythmias - a dangerous type of heart rhythm disorder that, in the worst case, can lead to cardiac arrest.