Final answer:
Multiform Atrial Tachycardia (MAT) is a type of heart rhythm disorder characterized by a fast heart rate that is irregular and has multiple different shapes on an electrocardiogram (ECG).
Step-by-step explanation:
Multiform Atrial Tachycardia (MAT) is a type of heart rhythm disorder. Arrhythmia refers to conditions where the heartbeat is irregular, too fast, or too slow. MAT is characterized by a fast heart rate that is irregular and has multiple different shapes on an electrocardiogram (ECG).