This 80-year-old woman with chronic obstructive lung disease has been admitted to the medical ICU with pneumonia:

• Multifocal Atrial Tachycardia (MAT)
• Left axis deviation
• Non-specific ST and T abnormality

Besides the presence of P waves with a different morphology, an important characteristic feature of MAT is the irregularity. Frequently, MAT is misdiagnosed as atrial fibrillation by ECG computer diagnostic programs.