In the context of a QRS complex, what does the term "nadir" refer to?

The term "nadir" in the context of a QRS complex refers to the lowest point of the complex. The QRS complex represents the depolarization of the ventricles in the heart, and identifying its nadir is important in various assessments of cardiac function. The nadir corresponds to the lowest point of the waveforms that make up the QRS, which typically occurs at the junction between the S wave (the negative deflection) and the subsequent T wave (the repolarization phase). Understanding this aspect of the QRS complex is essential for interpreting ECGs accurately and assessing ventricular function and conduction abnormalities. Recognizing the nadir can help in diagnosing conditions such as bundle branch blocks or ventricular hypertrophy, where alterations in the morphology of the QRS complex may be present.