As a medical professional with expertise in cardiology, I can provide you with an accurate description of the S wave in an ECG. The S wave in an Electrocardiogram (ECG) is the first downward deflection of the QRS complex that follows the R wave. The QRS complex represents the electrical activity of the ventricles as they depolarize during a heartbeat. The R wave is the first and usually the tallest positive deflection of the QRS complex, indicating the beginning of ventricular depolarization. The S wave signifies the subsequent part of the ventricular depolarization process. It's important to note that the presence of an S wave can vary among different leads of the ECG. In some leads, the S wave might not be visible, while in others, it can be quite prominent. The depth and prominence of the S wave can be influenced by various factors, including the heart's position within the chest, the angle of the electrical forces relative to the ECG lead, and the individual's cardiac anatomy. read more >>

The S wave is the first downward deflection of the QRS complex that occurs after the R wave. However, a S wave may not be present in all ECG leads in a given patient.read more >>