Multi-focal Atrial Tachycardia is characterized by what feature in P waves?

Multi-focal Atrial Tachycardia (MAT) is distinguished by the presence of multiple ectopic P waves that exhibit different morphologies. This occurs due to the activation of multiple ectopic foci within the atria, each having its own characteristic electrical impulse. As a result, the P waves on the electrocardiogram (ECG) will vary in shape and size, indicating the different origins of the electrical impulses.

In MAT, it's not just one ectopic focus causing the atrial activity, which would result in a single ectopic P wave, nor are the P waves normal as would be found in a healthy sinus rhythm. The absence of P waves is characteristic of different arrhythmias, such as atrial fibrillation. Thus, the defining characteristic of MAT is the presence of at least two different P wave morphologies, confirming the diagnosis and helping to guide appropriate treatment.