J POINT IN ECG AND ITS INERPRETATION IN ECG

J POINT IN ECG

1. J POINT Dr.G.VENKATA RAMANA MBBS DNB FAMILY MEDICINE

2. J POINT J unction between the termination of the QRS complex and the beginning of the ST segment The  J (junction) point  in the ECG is the point where the QRS complex joins the ST segment It represents the approximate end of depolarization and the beginning of repolarization as determined by the surface ECG There is an overlap of around 10ms. The J point marks the end of the QRS complex, and is often situated above the baseline, particularly in healthy young males

3. The J point may deviate from the baseline in early repolarization, epicardial or endocardial ischaemia or injury, pericarditis, RBBB, LBBB, RVH, LVH or digitalis effect On most ECGs the determination of the J point as a demarcation between QRS and the start of the ST is clear However with the advance of electrophysiological studies and scrutiny of the cellular/ionic mechanisms at each stage of the ECG – these lines become blurred

4. For simplicity: J point  is present in all ECGs and marks the transition of QRS complex to ST segment J wave deflection  occurs before the J point The position of the J point in relation to a slurred terminal QRS is still debated J point in a) normal; b) c) J point elevation; d) J point depression; e) with J wave (Osborn wave)

5. Note: The letter J on the ECG defines 2 totally different and unrelated events The  J point  is a point in time marking the end of the QRS and the onset of the ST segment present on all ECG’s T he  J wave  is a much less common long slow deflection of uncertain origin originally described in relation to hypothermia

6. Abnormalities of the J point Elevation or depression of the J point is seen with the various causes of  ST segment abnormality It may be elevated as a result of injury currents during acute myocardial ischemia and pericarditis, as well as in various other patterns of both normal and abnormal ECGs Elevation of the J point occurs with  benign early repolarisation A positive deflection  prior  to the J point is termed a  J wave (Osborn wave)  and is characteristically seen with  hypothermia