Which of the following is a cause of long QT syndrome?

Long QT syndrome is characterized by an extended QT interval on an electrocardiogram, which can lead to life-threatening arrhythmias such as Torsades de Pointes. One of the recognized causes of long QT syndrome is the use of certain medications, and macrolides, a class of antibiotics including drugs like erythromycin and azithromycin, are known to be associated with this condition. They can prolong the QT interval by interfering with cardiac repolarization, resulting in increased risk of arrhythmias.

In contrast, other options like coronary artery disease, congenital heart defects, and diabetes mellitus may have various effects on heart health but are not direct or well-established causes of long QT syndrome. While these conditions can lead to changes in heart function and possibly arrhythmias, they do not specifically and consistently lead to the prolonged QT interval characteristic of long QT syndrome. Macrolides directly influence the cardiac ion channels responsible for repolarization, making them a clear and recognized cause of this important condition.