The QRS comxplex in an ECG is not related to :

Options

A. Ventricular contraction
B. A measure of determining the heartbeat
C. Stroke volume of the cardiac cycle
D. Ventricular repolarisation

Answer

To solve the question regarding the QRS complex in an ECG, we will analyze each option provided and determine which one is not related to the QRS complex.

### Step-by-Step Solution:

1. **Understanding the QRS Complex**:
- The QRS complex in an ECG represents the depolarization of the ventricles. This is the electrical activity that triggers the contraction of the ventricles, leading to the pumping of blood out of the heart.

2. **Analyzing the Options**:
- **Option 1: Ventricular contraction**:
- The QRS complex is indeed related to ventricular contraction as it represents the depolarization of the ventricles, which leads to their contraction. This option is related.
- **Option 2: A measure of determining the heartbeat**:
- The QRS complex is part of the ECG waveform that helps in determining the heart rate. Thus, this option is also related.
- **Option 3: Stroke volume of the cardiac cycle**:
- While the QRS complex does not directly measure stroke volume, it is indirectly related because ventricular contraction affects stroke volume. However, it is not a direct measurement. This option is somewhat related but not directly.
- **Option 4: Ventricular repolarization**:
- The QRS complex does not represent ventricular repolarization; that is represented by the T wave. Therefore, this option is not related to the QRS complex.

3. **Conclusion**:
- The QRS complex is not related to **ventricular repolarization**. Hence, the correct answer is **Option 4**.

### Final Answer:
The QRS complex in an ECG is not related to **ventricular repolarization** (Option 4).