What is the primary risk factor for developing torsades de pointes?

The primary risk factor for developing torsades de pointes is the presence of a long QT interval. Torsades de pointes is a specific type of polymorphic ventricular tachycardia that is often associated with prolongation of the QT interval, which can lead to abnormal electrical activities in the heart.

A long QT interval can be caused by various factors, including genetic conditions, certain medications, and electrolyte imbalances. When the QT interval is prolonged, it indicates that the heart’s electrical system takes longer than normal to reset after each heartbeat. This delay can make the heart more susceptible to developing arrhythmias like torsades de pointes, where the heart's electrical activity becomes rapidly unstable.

In contrast, reentrant cardiac pathways involve a different mechanism of arrhythmia and are not specifically linked to torsades de pointes. An irregular heart rate can be a symptom of many types of arrhythmias, but it does not directly cause torsades de pointes. Similarly, a short QT interval is generally not associated with this specific type of arrhythmia and can be related to different cardiac issues. Therefore, the long QT interval stands out as the main risk factor for the development of torsades de pointes.