Patient Care Technician (PCT) AAH Practice Exam

What does the R-R interval measure in electrocardiography?

1. Distance from the end of one P wave to the next

2. Peak of the R wave to peak of the next R wave

3. Time between a ventricular contraction and the next

4. Time spent in diastole

The correct answer is: Peak of the R wave to peak of the next R wave

The R-R interval is specifically defined as the time duration between the peak of one R wave to the peak of the following R wave in an electrocardiogram (ECG). This measurement is crucial for determining heart rate and assessing the rhythm of the heart. By measuring the R-R interval, healthcare professionals can calculate the number of beats per minute (bpm), which is essential for evaluating a patient's cardiac function and identifying any arrhythmias. In the context of the other answer options, the distance from the end of one P wave to the next relates to atrial depolarization and does not reflect the ventricular activity captured by the R-R interval. The time between a ventricular contraction and the next is less specific compared to the R-R interval, since the R wave directly provides the intervals between ventricular depolarizations. Lastly, the time spent in diastole is the period when the heart muscle relaxes after contraction, which is not directly represented by the R-R interval. Thus, the measurement of the R-R interval is a precise indicator of cardiac cycle dynamics, focusing specifically on the ventricular electrical activity.