Which of the following events is not recorded on the surface ECG?

Options

A. Atrial depolarization
B. Atrial repolarization
C. Ventricular depolarization
D. Ventricular repolarization

Answer

To determine which event is not recorded on the surface ECG, we need to analyze the components of the ECG and what they represent in the cardiac cycle.

### Step-by-Step Solution:

1. **Understand the ECG Components**:
- The ECG consists of several key components: P wave, QRS complex, and T wave.
- Each of these components corresponds to specific electrical events in the heart.

2. **Identify the Events Represented**:
- **P Wave**: Represents atrial depolarization (the electrical activity that leads to the contraction of the atria).
- **QRS Complex**: Represents ventricular depolarization (the electrical activity that leads to the contraction of the ventricles).
- **T Wave**: Represents ventricular repolarization (the process of the ventricles relaxing after contraction).

3. **Consider the Events Not Recorded**:
- The question asks for an event that is not recorded on the surface ECG.
- While the ECG captures atrial depolarization (P wave), ventricular depolarization (QRS complex), and ventricular repolarization (T wave), it does not record atrial repolarization.

4. **Conclusion**:
- Therefore, the event that is not recorded on the surface ECG is **atrial repolarization**.

### Final Answer:
The event that is not recorded on the surface ECG is **atrial repolarization**.

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