Understanding an ECG, also referred to as an EKG, involves a basic knowledge of how the heart works and what the different lines recorded by the ECG machine represent. While many factors play a role in an ECG reading, understanding an ECG mainly involves checking that the spikes on the chart — which represent a heartbeat — are evenly spaced and the lines between them are smooth and not too jagged. Irregular spacing can mean a problem with the heart rhythm, though in some cases it can also mean the patient moved during testing or part of the ECG machine is not working properly.
An ECG machine records and displays the electrical impulses of a heart as it beats. The paper these results print on is often referred to as an ECG strip or rhythm strip, and understanding an ECG is simply the ability to read an ECG strip. The ECG machine can be used to determine a patient's heart rate and check for irregularities in rhythm, among other things. It cannot, however, determine blood pressure or perform other tests, which a doctor may need depending on the results from the ECG.
On the chart, spikes indicate the heart beating while the smoother lines between the sudden spikes indicate time between beats. The most important part of understanding an ECG is looking at the spikes, known as the QRS complexes in medical terms. Counting the number of QRS complexes found in a six-second time frame on the ECG strip and multiplying by 10 will determine the patient's heart rate. For example, eight beats in six seconds leads to the result of approximately 80 beats per second. The average heart rate for a patient is between 60 and 100 beats per minute.
The distance between the QRS complexes is also used to determine regular or irregular heartbeat. In understanding an ECG, calculating heart rate and determining the regularity of it are the most common tasks performed. If the space between the QRS complexes is consistent across the strip, the heartbeat is regular. Other problems can still occur though, even with a regular heart beat.
When too much or too little space appears between QRS complexes, even if the pattern is uniform throughout, it can indicate a heart rate that is slower or faster than normal. This problem should be examined further. Running a second ECG test is advisable to ensure that the test is accurate. Other causes for running a second test include a ECG strip with extremely spiky lines, random patterns, or when the test simply did not generate a proper readout.
