On J Point
The J point represents the end of depolarization and the beginning of repolarization as determined by the surface ECG. The term J deflection has been used to designate the formation of the wave produced when there is a large, prominent deviation of the J point from the baseline. The J deflection has been called many names, including camel-hump sign, late delta wave, J-point wave, and Osborn wave.
Beside hypothermia some other causes of J deflection are
- hypercalcemia,
- brain injury,
- subarachnoid hemorrhage,
- damage to sympathetic nerves in the neck, and
- cardiopulmonary arrest from oversedation
All J-wave deflections do not look alike. Some are merely elevations of ST segments in leads V1 and V2, whereas others are of the spike-and-dome variety. This leads to the conclusion that different mechanisms may be responsible for the size and shape of J-wave deflections.
*The prominent J deflection attributed to hypothermia was first reported in 1938 by Tomaszewski but the unusual wave increasingly has been called an Osborn wave after Osborn's article written in 1953
