How is the mean QRS vector determined?

How is the mean QRS vector determined?

• A. By calculating the heart rate
• B. By summing all ventricular vectors
• C. By measuring the electrical potential in lead II
• D. By assessing the P-wave duration

Answer: (B)

The mean QRS vector is determined by summing all ventricular vectors. This vector represents the overall direction and magnitude of the electrical activity during ventricular depolarization, which is captured during the QRS complex of an EKG.

To understand this better, each lead on an EKG measures the electrical activity of the heart from different angles. The individual QRS vectors obtained from each lead represent the electrical forces produced by the ventricles at that specific moment. By vectorially summing these individual QRS vectors, a mean vector can be calculated. This mean QRS vector gives a clearer picture of the net direction of depolarization in the heart, which can provide insights into the patient's cardiac health and potential abnormalities.

The other options do not accurately relate to the determination of the mean QRS vector. Heart rate does not reflect vector direction, electrical potential in lead II focuses on one perspective rather than summing vectors, and assessing P-wave duration pertains to atrial depolarization, not ventricular activity represented by the QRS complex.