The J point is the point on an electrocardiogram (ECG) representing the junction between the QRS complex and the ST segment. More specifically, it's where the QRS complex ends and the ST segment begins. It's often defined as the beginning of the ST segment.
The J point's position and morphology (especially elevation or depression relative to the baseline) are crucial in identifying various cardiac conditions, most notably myocardial infarction (heart attack), pericarditis, and early repolarization. While the definition is straightforward, pinpointing the precise "point" can sometimes be challenging on an ECG tracing.
Because of its importance, the J-point is a focus of study.
