Electrocardiography is the process of recording the heart's electrical activity through an electrocardiogram (ECG) via electrodes on the skin. A normal ECG shows a regular sinus rhythm with specific characteristics in wave patterns, intervals, and segments, all falling within defined normal ranges. Key components of interpretation include the rate, rhythm, cardiac axis, and the shapes and measurements of the P wave, QRS complex, ST segment, and T wave.

1. ELECTROCARDIOGRAPHY
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2. ELECTROCARDIOGRAPHY
Electrocardiography is the process of producing
an electrocardiogram, a recording – a graph of
voltage versus time – of the electrical activity of
the heart using electrodes placed on the skin.
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8. Normal ECG
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9. Normal ECG
A normal ECG is illustrated above. Note that the heart is beating in a
regular sinus rhythm between 60 - 100 beats per minute (specifically
82 bpm). All the important intervals on this recording are within
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10. Normal ECG
1. P wave:
• upright in leads I, aVF and V3 - V6
• normal duration of less than or equal to 0.11 seconds
• 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
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11. Normal ECG
2. PR interval:
• Normally between 0.12 and 0.20 seconds.
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12. Normal ECG
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.
• 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.
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13. Normal ECG
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
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14. Normal ECG
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
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15. Normal ECG
6. QT interval:
• Durations normally less than or equal to 0.40
seconds for males and 0.44 seconds for
females.
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17. Step-by-Step ECG Interpretation
• Rate
• Rhythm
• Cardiac axis
• P- wave
• PR-interval
• QRS complex
• ST segment
• QT interval
(include T and U wave)
• Other ECG signs
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24. Cardiac Axis
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25. Cardiac Axis
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26. ANATOMIC GROUPS
I
LATERAL
aVR
NONE
V1
SEPTAL
V4
ANTERIOR
II
INFERIOR
aVL
LATERAL
V2
SEPTAL
V5
LATERAL
III
INFERIOR
aVF
INFERIOR
V3
ANTERIOR
V6
LATERAL
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27. Step-by-Step ECG Interpretation
• Rate
• Rhythm
• Cardiac axis
• P- wave
• PR-interval
• QRS complex
• ST segment
• QT interval(include T and U wave)
• Other ECG signs
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47. THANK YOU
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