• ECG Device and Millivolts
• Electrical Vectors and ECG Calibration
• 12-Lead ECG and Calibration
• Calibration Mark
• ECG Amplitude
• ECG Amplitude and Calibration
• ECG Paper Speed and Calibration

ECG Device and Millivolts

Millivolts and the ECG Curve

• During the cardiac cycle, the heart generates electric vectors
• ECG electrodes placed on the patient's body detect the electric voltage of the vectors in millivolts
• ECG device
• Converts millivolts into an ECG curve
• Has 10 electrodes placed on the body, which detect electric vectors
• Displays the vectors on ECG paper in 12 ECG leads

12-Lead ECG and Calibration

Calibration Mark and ECG Paper

• ECG paper almost always has a calibration mark at the beginning
• Calibration mark
• Is a vertical rectangle (5x10mm) at the start of the paper
• provides information about the speed of the ECG paper and the height of the 1mV amplitude

ECG Amplitude

• ECG curve amplitude (height, depth) depends on:
• Direction and magnitude of the electrical vector
• Calibration
  
  
• ECG curve amplitude
• is used in ECG diagnostics
• e.g., left ventricular hypertrophy and right ventricular hypertrophy
  
  
• If all QRS complexes on the ECG are:
• very high or low
• consider calibration
  
  
• Amplitude in mm corresponds to electrical voltage
• 14mm = 1.4mV
• 7mm = 0.7mV
  (with standard calibration 1mV = 10mm)

ECG Paper Speed and Calibration

• The standard ECG paper speed is 25mm/s
• At this speed, the calibration mark has a width of 5mm
• Sometimes a speed of 50mm/s is used (for diagnosing supraventricular tachycardia)
• ECG paper moves twice as fast, so the ECG curve and calibration mark are twice as wide
• The calibration mark has a width of 10mm
  
  
• The following two ECG papers are from the same patient

Paper speed 25mm/s

• Calibration mark width 5mm

Paper speed 50mm/s

• ECG curve is twice as wide
• Calibration mark width 10mm

Calibration 20mm

• This is the same patient as in the previous ECG
• We set the calibration to 20mm (calibration mark on the right)
• ECG amplitude is thus twice as large
• P waves (red arrows) are revealed before the QRS complexes
• The patient has numerous atrial extrasystoles
• Does not have atrial fibrillation

Dual Calibration 10/5mm

• This is the same patient as in the previous ECG
• The ECG has dual calibration (calibration mark has 2 amplitudes)
• Limb leads have a calibration of 10mm
• Precordial leads have a calibration of 5mm
• QRS complexes in precordial leads
• Are 2x lower than in the previous ECG
• Voltage criteria for left ventricular hypertrophy need to be doubled
• QRS height in V6 is 30mm (15x2)

Calibration 20mm

• This is the same patient as in the previous ECG
• With 20mm calibration, the ECG amplitude is 2x larger
• The delta wave is revealed (red arrows)
• The patient has WPW syndrome