Which interval measures the time between atrial contraction and the beginning of ventricular contraction?

Which interval measures the time between atrial contraction and the beginning of ventricular contraction?

• A. QRS Complex
• B. P Wave
• C. PR Interval
• D. PR Segment

Answer: (C)

The interval in question is measured from the start of atrial depolarization to the start of ventricular depolarization. This is the PR interval. It captures the time the electrical impulse takes to travel from the atria through the AV node and into the ventricles, including the brief delay at the AV node that allows the ventricles to fill before they contract. Remember how the waves fit together: the P wave corresponds to atrial depolarization (atrial contraction), the PR interval ends at the beginning of the QRS complex (ventricular depolarization). The PR segment, by contrast, is the flat portion within that interval reflecting conduction through the AV node, not the entire interval itself. So the PR interval best represents the time between atrial contraction and the start of ventricular contraction.

The interval in question is measured from the start of atrial depolarization to the start of ventricular depolarization. This is the PR interval. It captures the time the electrical impulse takes to travel from the atria through the AV node and into the ventricles, including the brief delay at the AV node that allows the ventricles to fill before they contract.

Remember how the waves fit together: the P wave corresponds to atrial depolarization (atrial contraction), the PR interval ends at the beginning of the QRS complex (ventricular depolarization). The PR segment, by contrast, is the flat portion within that interval reflecting conduction through the AV node, not the entire interval itself.

So the PR interval best represents the time between atrial contraction and the start of ventricular contraction.