Which of the following is a potential long-term effect of Lithium on the heart?

The correct choice highlights that a potential long-term effect of Lithium on the heart can be junctional escape, which refers to an escape rhythm originating from the junctional tissue of the heart. Lithium, commonly used in the treatment of bipolar disorder, can affect the cardiovascular system, particularly with prolonged use. It can cause changes in the conduction system of the heart, which may lead to junctional rhythms.

Junctional escape rhythms are often a compensatory mechanism when the normal pacemaker activity of the heart (the sinoatrial node) is compromised or when there's a block in the conduction pathway. In this case, the heart can utilize junctional tissues as an alternative pacemaker, which may be a response to long-standing Lithium use and diminished electrical conduction.

In contrast, while arrhythmia, hypertension, and atrial fibrillation can potentially occur with Lithium use, they do not specifically illustrate the unique mechanism involving the junctional escape that relates directly to Lithium’s impact on cardiac conduction. These conditions would indicate different pathways of cardiac effects associated with various health factors unrelated to the specific conduction issues induced by Lithium.