A 74-year-old woman with a long history of obstructive lung disease and asthma is on the respirology ward with severe bronchopneumonia:

• Multifocal atrial tachycardia (153/min)
• Frequent aberrantly conducted complexes (Ashman phenomenon)
• Non-specific ST and T abnormality

Comment: There is a very rapid (153/min), very irregular arrhythmia that was misdiagnosed by the computer as atrial fibrillation. Criteria for multifocal atrial tachycardia includes at least 3 different P-wave morphologies with varying PP and PR intervals.