Certified Cardiovascular Technician Practice Exam

Which wave on an electrocardiogram indicates atrial depolarization?

1. T wave

2. P wave

3. QRS complex

4. U wave

The correct answer is: P wave

The P wave on an electrocardiogram signifies atrial depolarization, which is the electrical process that triggers the atria to contract and pump blood into the ventricles. During the P wave, the electrical impulse originating from the sinoatrial (SA) node spreads through the right and left atria, resulting in their depolarization. This wave is typically the first deflection observed in a normal ECG tracing. In contrast, other waves such as the T wave and QRS complex represent different electrical activities: the QRS complex indicates ventricular depolarization (which leads to ventricular contraction), and the T wave reflects ventricular repolarization (the recovery phase after contraction). The U wave is less commonly seen and is not directly associated with atrial depolarization. Understanding the significance of the P wave is crucial for interpreting ECG readings and assessing cardiac function, as it directly indicates the health and efficiency of atrial activity.