As a medical professional with expertise in cardiology, I can explain the significance of the PR interval in an electrocardiogram (ECG) reading. The PR interval represents the time it takes for an electrical impulse to travel from the atria to the ventricles. This journey begins with the atrial depolarization, which is the initial contraction of the atria to pump blood into the ventricles, and ends with the ventricular depolarization, which is the subsequent contraction of the ventricles to pump blood out to the body. In a normal ECG, the PR interval is typically between 0.12 to 0.20 seconds. It's a crucial measure because it reflects the time required for the electrical signal to pass through the atrioventricular (AV) node, which is the only electrical pathway between the atria and ventricles. Any prolongation or shortening of the PR interval can indicate various cardiac conditions, such as heart block or pre-excitation syndromes. read more >>

The period of time from the onset of the P wave to the beginning of the QRS complex is termed the P-R interval, which normally ranges from 0.12 to 0.20 seconds in duration. This interval represents the time between the onset of atrial depolarization and the onset of ventricular depolarization.read more >>