Which condition is characterized by an abnormal heart rhythm?

The condition characterized by an abnormal heart rhythm is arrhythmia. Arrhythmia encompasses a wide range of heart rhythm disorders that can manifest as a heartbeat that is too fast, too slow, or irregular. This condition can result from various issues, including problems with the heart's electrical system, structural abnormalities, or underlying health conditions, and can lead to symptoms such as palpitations, dizziness, or even loss of consciousness.

In contrast, hypertension refers to high blood pressure, which affects the force of blood against artery walls but does not necessarily imply issues with heart rhythm. Edema involves swelling caused by excess fluid trapped in the body's tissues, which is not related to heart rhythm. An aneurysm is a localized enlargement of an artery caused by the weakening of the artery wall, and while it can pose serious health risks, it does not involve the concept of abnormal heart rhythms. Thus, arrhythmia is the only option that directly addresses abnormal heart rhythm conditions.