Definition

  Postextrasystolic U wave augmentation is a marked increment in U wave amplitude

      after ventricular premature complexes (VPCs).




Implications of postextrasystolic augmentation of U wave

  Postextrasystolic U wave augmentation is a well-recognized adverse prognostic sign in patients with

      the "pause-dependent long QT syndrome
".

      Patients with a prolonged QT interval showing bizarre TU complexes after PVCs are prone to

      the development of torsades de pointes and ventricular fibrillation.

 
In patients without the long QT syndrome, postextrasystolic U wave changes

      may be a specific marker of a tendency to the development of spontaneous ventricular arrhythmias.

  On the other hand, postextrasystolic T wave changes are common in patients without long QT syndrome

      and lack predictive value.




References

  J Am Coll Cardiol 1996;28:1746-1752.

  Prog Cardiovasc Dis 1988;31:115-172.

  J Am Coll Cardiol 1983;2:806-817.

  J Am Coll Cardiol 1995;25:1564-1575.

  Br Heart J 1977;4:371-374.





ECG 1a. The ECG above is from a 52 years-old man who had experienced acute anterior myocardial infarction 7 months ago.
After the infarction, he had undergone coronary artery bypass surgery for 3 vessel disease.
Now, he has left ventricular anterior and inferior wall aneurysms with a very depressed left ventricle (EF 25%).
The ECG above shows
ventricular trigeminy.
The P wave of the postextrasystolic beat seems to have normal duration.
The P wave of the second postextrasystolic beat seems to be widened: interatrial block?

Click here for a more detailed ECG




ECG 1b. Above is his immediately repeated ECG. This time, it was recorded at a calibration of 20 mm/mV.
This ECG clearly shows that
the augmented U wave of the postextrasystolic beat fuses with the P wave of the second
postextrasystolic beat
. This fusion results in a wide P wave and gives the impression of intermittent interatrial block, at first
glance.
The P wave of the first postextrasystolic beat has a normal width since it has not been deformed by an augmented U wave.

Click here for a more detailed ECG