Question

Which portion of the ECG corresponds to repolarization (i.e. relaxation) of the atria? a. \(\mathrm{P}\) wave b. QRS complex c. T wave d. none of the above: atrial repolarization is masked by ventricular depolarization

Short answer

Answer: (b) QRS complex

Step-by-step solution

Understanding the ECG components

An ECG has three main components: - P wave: represents atrial depolarization (i.e. contraction) - QRS complex: represents ventricular depolarization (i.e. contraction) and atrial repolarization (i.e. relaxation) - T wave: represents ventricular repolarization (i.e. relaxation)

Matching the ECG components with atrial repolarization

Now, we need to find which of these components represents atrial repolarization (i.e. relaxation) among the given choices: a. P wave: represents atrial depolarization, not repolarization b. QRS complex: represents both ventricular depolarization and atrial repolarization c. T wave: represents ventricular repolarization, not atrial repolarization d. none of the above

Concluding the answer

Based on the matching in Step 2, we can see that the atrial repolarization is represented by the QRS complex. Therefore, the correct answer is option (b) QRS complex.