During multifocal atrial tachycardia, the P-waves are of different morphology, because

• A. Normal sinus node pacing
• B. Abnormal automaticity, multiple foci in the atria firing causing varying P wave morphology
• C. AV nodal reentry
• D. Uniform conduction

Answer: (B)

During multifocal atrial tachycardia, several atrial pacemaker sites fire irregularly because of abnormal automaticity. Each focus activates the atria in a different way, so the P waves change shape from beat to beat. This beating pattern creates multiple P-wave morphologies and an irregular rhythm with a rate typically over 100 bpm. In contrast, a single sinus node pacing would produce uniform P waves, and reentrant mechanisms like AV nodal reentry would not generate multiple distinct P-wave morphologies. Uniform conduction also would not yield varying P waves.