Final answer:
To determine the heart rate from an ECG, count the number of QRS complexes over a specific time and multiply by an appropriate factor or use the standard formula dividing 1500 by the number of small squares between two QRS complexes. An increased frequency of QRS complexes indicates a higher than normal heart rate.
Step-by-step explanation:
To determine the heart rate in beats per minute (bpm) using an electrocardiogram (ECG or EKG), we start by looking at the series of waves and complexes on the ECG. The QRS complex, which represents the rapid depolarization of the right and left ventricles, is the most noticeable set of spikes on an ECG trace and is used to measure the frequency of heartbeats. Assuming a constant time between beats, you count the number of QRS complexes that occur in a given time frame and calculate the beats per minute.
If, for instance, you count the number of QRS complexes over a 10-second period, multiplying this count by 6 will give you the heart rate in bpm. If the ECG machine is calibrated so that each small square represents 0.04 seconds, you can count the number of small squares between two consecutive QRS complexes and divide 1500 by this number to get the bpm (assuming a standard paper speed of 25 mm/s).
In a case where the pattern is abnormal, as mentioned with increased frequency of QRS complexes, it suggests an increased heart rate or tachycardia. If the frequency between QRS complexes has increased, we would expect the heart rate (pulse) to be higher than normal.