Which symptom is characterized by a fast, pounding, and irregular heartbeat?

Palpitations refer to the sensation of feeling an abnormal heartbeat, which can present as a fast, pounding, or irregular rhythm. This symptom often arises from various underlying conditions, such as arrhythmias, anxiety, or even excessive caffeine intake. The key characteristic of palpitations is that the individual becomes aware of their heartbeat, which can be perceived as racing or irregular, making it distinct from other symptoms that might not involve a direct awareness of the heart's activity.

Other symptoms listed, like syncope, dizziness, and chest heaviness, may accompany cardiovascular issues but do not describe the specific sensation of an irregular heartbeat as clearly as palpitations do. Syncope typically involves fainting or loss of consciousness, while dizziness often refers to lightheadedness or a feeling of imbalance. Chest heaviness, on the other hand, can indicate discomfort or pressure but does not specifically relate to the heartbeat's rhythm or frequency. Therefore, palpitations is the most accurate description of experiencing a fast, pounding, and irregular heartbeat.