# With the electrocardiograph, how to read the electrocardiogram?

Recently, we received such a consultation: I bought an electrocardiograph at home, but I can't read the electrocardiogram. Some people may have encountered a similar situation. So, what should we do in this situation? Don't worry, editor will teach you how to read the electrocardiogram.

The most basic measurement parameters of ECG chart include heart rate, P wave time, P-R interval, QRS time, Q-T interval, average cardiac axis, etc.

**1. What do the squares on the ECG chart represent?**

There are two thick and thin vertical and horizontal lines on the ECG recording paper.

The vertical line represents the voltage, expressed in mV, and can be expressed in mm in special cases.

The horizontal line represents time, expressed in s or ms.

Usually the paper feed speed of ECG recording is 25mm/s, so each small grid represents 0.04s, and each large grid (5 small grids) represents 0.2s.

The calibration voltage is 10mm (10 small divisions) is 1mV, so each small division represents 0.1mV, and each large division represents 0.5mV.

Select the leads with clearer bands and measure them with a divider.

When measuring the voltage of the positive wave, it should be measured from the upper edge of the baseline to the highest point of the wave; when measuring the negative voltage, it should be measured from the lower edge of the baseline to the lowest point of the wave.

The measurement time shall be measured from the leading edge of the beginning of a wave to the leading edge of the end of the wave. In short, the effect of the baseline should be removed from the measurement.

**2. Heart rate measurement**

Heart rate measurement is a crucial step in ECG measurement. At present, there are five main methods for measuring heart rate.

**Method 1: Scale measurement**

Use a subscale to measure the P-P or P-R distance, multiply the measured seconds by 100, and then use the table look-up method to calculate the heart rate.

**Method 2: Scale measurement**

Use a subscale to measure the P-P or P-R distance, divide the measured seconds by 60, and the resulting quotient is the heart rate.

**Method 3: Simple visual method**

The commonly used paper feeding speed of the electrocardiograph is 25mm/s, that is, 5 large grids, so the time for each large grid is 0.2s. At present, the P-P or P-R distance occupies several large grids, and the heart rate can be calculated.

If it is 3, 4 or 5 large grids, the heart rate is 100 beats/min, 75 beats/min, and 60 beats/min, respectively.

**Method 4: ECG measuring ruler**

Heart rate can be measured using an electrocardiogram ruler.

**Method 5: Measurement method when arrhythmia is irregular**

1. Divide the average value of multiple P-P or P-R distances by 60 to get the heart rate

2. In case of atrial fibrillation, continuously count the number of R waves in the example for 10s, multiply by 6, and calculate the average ventricular rate.

The above editor introduced to you how to look at ECG drawings. If you have a need for customization of ECG drawings, you can consult online.