How is heart rate accurately measured using an ECG?

The accurate measurement of heart rate using an electrocardiogram (ECG) primarily involves assessing the intervals between specific waves that correspond to the electrical activities of the heart's cycles. The correct approach is to measure the time between P waves, which represents the atrial depolarization.

In a standard ECG, each P wave indicates the initiation of a heartbeat, and the distance between these waves correlates with the time taken for the atria to contract and prepare for the subsequent ventricular contraction. By determining the time interval between successive P waves, you can calculate the heart rate efficiently, as this reflects the frequency of atrial depolarization.

While other components such as the QRS complex and T waves do capture significant phases of the cardiac cycle, they are primarily involved in different aspects of heart function—ventricular depolarization and repolarization, respectively—and are not as directly linked to atrial activity as the P wave measurement. Therefore, focusing on P waves is crucial for determining the heart rate accurately.