Final answer:
The P-Q interval in an ECG pattern indicates the time it takes for the cardiac impulses to travel from the sinus node, through the atrium, past the AV node, and on to the ventricles. It includes the atrial depolarization and the beginning of ventricular depolarization, and is important for diagnosing heart conditions.
Step-by-step explanation:
The P-Q interval, also known as the PR interval, is a key component of an electrocardiogram (ECG) that measures the time it takes for the electrical impulse to travel from the sinus node through the atrium, and then through the atrioventricular (AV) node before it reaches the ventricles. This interval includes the P wave, which signifies atrial depolarization, and the beginning of the QRS complex, which reflects ventricular depolarization. If there's a delay in the transmission of the impulse from the SA node to the AV node, it will be reflected as a longer P-Q interval on the ECG.
Importantly, during the P-Q interval, the atria contract and begin to relax, and the ventricles are about to start their contraction. This sequence ensures the coordinated pumping action of the heart, where the atria fill the ventricles with blood before they contract. Clinically, monitoring the PR interval is essential for diagnosing various heart conditions.