Final answer:
The statement that P-R intervals being the same means they are constant is true. It reflects stable conduction from the sinus node through the AV node in the heart.
Step-by-step explanation:
If the P-R intervals are the same, they are indeed said to be constant. The P-R interval is the time between the onset of the P wave and the start of the QRS complex on an electrocardiogram (ECG), reflecting the time the electrical impulse takes to travel from the sinus node through the AV node. When these intervals are consistent across multiple heartbeats, it indicates that the conduction pathway has stable conduction properties. Therefore, the statement is true.