Which ECG finding is diagnostic for Multifocal Atrial Tachycardia?

Which ECG finding is diagnostic for Multifocal Atrial Tachycardia?

• A. Three or more P-wave morphologies
• B. Delta wave
• C. Short PR interval
• D. T-wave inversion

Answer: (A)

Multifocal atrial tachycardia is diagnosed on ECG by the presence of three or more distinct P-wave morphologies before the QRS complexes. This reflects at least three different atrial pacemaker sites firing independently, producing multiple, different-shaped P waves while the rhythm remains tachycardic and usually irregular. The key feature is the variability of P waves with an irregular rhythm, which sets MAT apart from other atrial tachyarrhythmias like atrial fibrillation (no discernible P waves) or classic atrial flutter (characteristic flutter waves). The other findings point to different conditions. A delta wave indicates preexcitation such as Wolff-Parkinson-White syndrome, and a short PR interval can also be seen with preexcitation. T-wave inversion is non-specific and not diagnostic for MAT.

Multifocal atrial tachycardia is diagnosed on ECG by the presence of three or more distinct P-wave morphologies before the QRS complexes. This reflects at least three different atrial pacemaker sites firing independently, producing multiple, different-shaped P waves while the rhythm remains tachycardic and usually irregular. The key feature is the variability of P waves with an irregular rhythm, which sets MAT apart from other atrial tachyarrhythmias like atrial fibrillation (no discernible P waves) or classic atrial flutter (characteristic flutter waves).

The other findings point to different conditions. A delta wave indicates preexcitation such as Wolff-Parkinson-White syndrome, and a short PR interval can also be seen with preexcitation. T-wave inversion is non-specific and not diagnostic for MAT.