What characterizes the rhythm of multifocal atrial tachycardia?

• A. Consistent P wave morphology
• B. Regular and fast ventricular rhythm
• C. Irregular rhythm with a fast rate
• D. Stable heart rate

Answer: (C)

The defining characteristic of multifocal atrial tachycardia is an irregular rhythm with a fast rate. In this condition, you will observe at least three distinct P wave morphologies due to ectopic foci in the atria firing at different rates. This leads to a rapid heart rate, typically exceeding 100 beats per minute, while the rhythm itself remains irregular due to the varying P wave shapes, indicating that multiple areas of the atrium are asynchronously generating impulses.

A consistent P wave morphology, on the other hand, would indicate a single ectopic focus, which is not consistent with multifocal atrial tachycardia. Similarly, a regular and fast ventricular rhythm suggests a different arrhythmia, such as atrial flutter or certain types of supraventricular tachycardias, where the rhythm is more organized. Stable heart rate is not a characteristic feature either, as multifocal atrial tachycardia is typified by a rapid and irregular heart rate that can fluctuate. Thus, the description of an irregular rhythm with a fast rate accurately captures the essence of multifocal atrial tachycardia.