ECG simplified learning Approach - all about waveforms, segments, intervals

3. Learning Objectives:
• Recognize normal waveforms, and know what
physiological event each represents.
• Identify intervals and segments on the ECG
• Understand basic conceptual significance of
abnormal intervals.

4. • This small red box covers the events of single cardiac cycle.

5. WAVEFORMS
• Waveforms are
caused by changes in
voltage as measured
between two points
on the body.
• Each waveform
represents a discrete
electrophysiological
events in the cardiac
cycle.

6. WAVEFORMS
• P wave: Atrial depolarization
• QRS complex: Ventricular
depolarization
• T wave: Ventricular
repolarization
• (U wave: Unknown)
P wave QRS
complex
T wave
U wave

7. WAVEFORMS
Characteristics used to
waveforms include:
• Duration
• Amplitude
• Morphology
P wave QRS
complex
T wave
U wave

8. WAVEFORMS
(More about the QRS complex)
Waveform Nomenclature:
• Wave having height of more than 5
mm : Capital latter (e.g. R wave)
• Wave having height of less than 5
mm : small latter (e.g. q wave, s
wave)
• Q/q wave: first negative deflection
in QRS complex
• R wave: First positive deflection in
QRS complex
• S wave: Negative deflection after R
wave in QRS complex.
q wave s wave
R wave
• R’ (prime) wave: second
positive deflection, after S
wave in QRS complex.

9. WAVEFORMS
(More about the QRS complex)
qRs Qr RS RsR’

10. SEGMENTS
• Segments connects
waveforms. (Simply
named by two end points)
• Characteristics used to
describe segments include:
• Morphology
PR
segment
ST
segment
TP
segment

11. INTERVALS
• Interval includes
waveform(s) +/- segment(s).
• PR interval = PR wave + PR
segment
• QRS interval = QRS
complex only
• QT interval = QRS complex
+ ST segment + T wave
• RR interval = Everything
Characteristics used to
waveforms include:
• Duration
PR interval =
PR wave + PR
segment
QRS interval =
QRS complex
only
QT interval =
QRS complex + ST
segment + T wave
RR interval = Everything

12. INTERVALS
PR interval =
PR wave + PR
segment
QRS interval =
QRS complex
only
QT interval =
QRS complex + ST
segment + T wave
RR interval = Everything
Inter
val
Normal
duration
Significance of abnormal
duration
PR 120 – 200
ms
• < 120ms: Abnormal
connection between atria
and ventricles (e.g. bypass
AV node)
• > 200ms: Delayed
conduction through AV
node (e.g. β – blocker, CCB,
Excessive input from the
vagus nerve)
QRS ≤ 120 ms • > 120ms: Abnormal
sequence of ventricular
depolarization or excessive
ventricular mass
QT ≤ ½ RR
interval
(an
approxima
tion)
• > ½ RR interval: Delayed
ventricular repolarization
(High risk of dangerous
arrhythmia)

13. • In the name of J point - J
stands for junction
• It is connection between S
wave with ST segment
The J point
J point