Q. Describe U - Waves?

The U-wave is usually upright if the T is also upright and is highest at low rates. When the heart rate increases to more than 90, the U-wave is rarely visible because it merges with the end of the T-wave and the ascending limb of the P-wave. Most of the workers believe that it represents after potentials of the T-wave. The U-wave is accentuated by a larger diastolic volume, hypokalemia and increased digitalis or calcium. Occasionally in patients with very low potassium, the U-wave can become so tall that it is mistaken for a tall T-wave. Patients with inverted U-waves may have an overload of central volume and the tall U-waves may represent a distended papillary muscle. In patients with CAD incidence of inverted or diphasic U-waves is about 30 per cent at rest and 62 per cent after exercise. If one makes an analysis of inverted U-waves, LVH is the most common cause; angina is responsible for about 20 per cent.