Long QT syndrome
Long QT syndrome may be present at birth or develop later in life. The inherited form may occur by itself or as part of larger genetic disorder. Onset later in life may result from certain medications, low blood potassium, low blood calcium, or heart failure. Medications that are implicated include certain antiarrhythmics, antibiotics, and antipsychotics. LQTS can be diagnosed using an electrocardiogram (EKG) if a corrected QT interval of greater than 480–500 milliseconds is found, but clinical findings, other EKG features, and genetic testing may confirm the diagnosis with shorter QT intervals.