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Learn ECG daily for PGMEE
#2
[Image: hAxRmK8.png]
The ECG Paper recorded at the speed of 25mm per second.


[Image: DKGpd1m.png]
A single large square with relation to time with length. 

For better understanding:

1 mm = 0.04 sec
2 mm = 0.08 sec
3 mm = 0.12 sec
4 mm = 0.16 sec
5 mm = 0.20 sec
10 mm = 0.40 sec
15 mm = 0.60 sec
20 mm = 0.80 sec
25 mm = 1.00 sec

[Image: L0IEYEQ.png]

The formation of different waves.
  • P wave-atrial depolarization
  • QRS complex-ventricular depolarization
  • ST segment, T wave-ventricular repolarization
  • P Wave: First wave seen, Small rounded, upright (positive) wave indicating atrial depolarization (and contraction)
  • PR Interval: Distance between beginning of P wave and beginning of QRS complex Measures time during which a depolarization wave travels from the atria to the ventricles
  • QRS Interval: Three deflections following P wave Indicates ventricular depolarization (and contraction)
  1. Q Wave: First negative deflection
  2. R Wave: First positive deflection
  3. S Wave: First negative deflection after R wave
  • ST Segment: Distance between S wave and beginning of T wave. Measures time between ventricular depolarization and beginning of re-polarization.
  • T Wave: Rounded upright (positive) wave following QRS. Represents ventricular repolarization
  • QT Interval: Distance between beginning of QRS to end of T wave. Represents total ventricular activity
  • U Wave: Small rounded, upright wave following T wave. Most easily seen with a slow HR. Represents repolarization of Purkinje fibers

[Image: 6f2TgW3.png]

A normal ECG is shown above. Note that the heart is beating in a regular sinus rhythm between 60 - 100 beats per minute (in above case 82 bpm). 

1.  P wave:
  • upright in leads I, aVF and V3 - V6
  • normal duration of less than or equal to 0.11-0.12  seconds and normal amplitude of less than or equal to 2.5 mm.
  • polarity is positive in leads I, II, aVF and V4 - V6; diphasic in leads V1 and V3; negative in aVR
  • shape is generally smooth, not notched or peaked
2. PR interval:
  •  Normally between 0.12 and 0.20 seconds.
3. QRS complex:
  • Duration less than or equal to 0.12 seconds, amplitude greater than 0.5 mV in at least one standard lead, and greater than 1.0 mV in at least one precordial lead. Upper limit of normal amplitude is 2.5 - 3.0 mV.
  • QRS amplitude is variable from lead to lead and from person to person. 2 determinant of QRS voltages are: Size of the ventricular chambers (i.e., the larger the chamber, the larger the voltage) and Proximity of chest electrodes to ventricular chamber (the closer, the larger the voltage)
  • small septal Q waves in I, aVL, V5 and V6 (duration less than or equal to 0.04 seconds; amplitude less than 1/3 of the amplitude of the R wave in the same lead).
  • represented by a positive deflection with a large, upright R in leads I, II, V4 - V6 and a negative deflection with a large, deep S in aVR, V1 and V2
  • in general, proceeding from V1 to V6, the R waves get taller while the S waves get smaller. At V3 or V4, these waves are usually equal. This is called the transitional zone.
4. ST segment:
  • isoelectric, slanting upwards to the T wave in the normal ECG
  • can be slightly elevated (up to 2.0 mm in some precordial leads)
  • never normally depressed greater than 0.5 mm in any lead
5. T wave:
  • T wave deflection should be in the same direction as the QRS complex in at least 5 of the 6 limb leads
  • normally rounded and asymmetrical, with a more gradual ascent than descent
  • should be upright in leads V2 - V6, inverted in aVR
  • amplitude of at least 0.2 mV in leads V3 and V4 and at least 0.1 mV in leads V5 and V6
  • isolated T wave inversion in an asymptomatic adult is generally a normal variant
6. QT interval:
  •  Durations normally less than or equal to 0.40 seconds for males and 0.44 seconds for females.
Who can see the Invisible, Can do the Impossible!

Messages In This Thread
Learn ECG daily for PGMEE - by acrosspg - 23-04-2018, 06:25 PM
The ECG Paper and Normal ECG - by acrosspg - 23-04-2018, 06:51 PM
Left and Right axis deviation - by acrosspg - 29-04-2018, 02:13 PM
Wandering Atrial Pacemaker (WAP) - by acrosspg - 10-05-2018, 03:30 PM
Multifocal Atrial Tachycardia - by acrosspg - 10-05-2018, 04:12 PM

 


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