ECG

ECG

3. DR ABDUL SAMI
MPHIL EASTERN MEDICINE
The Islamia University of
Bahawalpur
Pakistan

4. Electrocardiography
Electrocardiographyisthetechniqueby
whichtheelectricalactivitiesofthe
heartarestudied.Thespreadof
excitationthrough myocardium
produceslocalelectricalpotential.This
causesflowofsmallcurrentsthrough
thebodywhichactsasvolume
conductor.Thesesmallcurrentscanbe
pickedupfromthesurfaceofthebody
byusingsuitableelectrodesand
recorded inthe form of
electrocardiogram.

5. ELECTROCARDIOGRAPH
Electrocardiographistheinstrument(ECGmachine)
bywhichtheelectricalactivitiesoftheheartare
recorded.

6. Electrocardiogram
Thisis(cardiology)thevisualoutputthatan
electrocardiographproduces.

7. ThepaperthatisusedforrecordingECGiscalled
ECGpaper.Electrocardiographicgridreferstothe
markings(lines)onECGpaper.ECGpaperhas
horizontalandverticallinesatregularintervalsof1
mm.Every5thline(5mm)isthickened.

8. ECGisrecordedbyplacingseriesofelectrodesonthe
surfaceofthebody.TheseelectrodesarecalledECGleads
andareconnectedtotheECGmachine.Electrodesare
fixedonthelimbs.Usually,rightarm,leftarmandleftleg
arechosen.Heartissaidtobeinthecenterofan
imaginaryequilateraltriangledrawnbyconnecting

9. Baseline or Isoelectricline: The flat or straight line present in the graph paper of
ECG.
Wave: Any deviation from baseline is called wave. Wave always starts from
baseline and ends on baseline.
Waveform: Movement away from the baseline, up or down.
Segment:A line between waveforms or a line (baseline) joining the two waves
(successive waves).
There are three segments in one ECG:-
1) PQ Segment
2) ST Segment
3) TP Segment
Complex: Two or more waves having no segment between them is called
complex. EgQRS complex in which there are three waves having no segment.

10. Interval: A waveform plus a segment is called interval.
PR Interval: The time duration between beginning of P
wave and beginning of QRS complex. Normal duration is
0.12 sec to 0.20 sec.
QRS Interval:Thetime duration in which ventricles
depolarize, it is also called ventricular activation (VAT). Its
normal duration is less than 0.11 sec.
QT Interval:Thetime duration between the beginning of Q
wave and end of T wave. Its normal duration is 0.35 sec.
RR Interval:Itis the time duration between two successive
R waves. Its normal duration is 0.8 sec.

13. Horizontally:
One small box (1mm)= 0.04 sec
One large box (5mm)= 0.20 sec
Five large boxes (25mm)= 1sec
Vertically:
One large box (5mm)= 0.5mv
Two large boxes (10mm)= 1mv

14. SA Node -Heart pacemaker; located in the RA;
initiates next step

15. P Wave -Atrial depolarization and contraction

16. AV Node -Slows the depolarization of the atria;
connects atria and ventricles electrically

17. QRS complex-ventricular depolarization; begins in
Bundle of His

18. ST Segment-Initial plateau phase of
ventricular repolarization

19. T wave -Rapid phase of ventricular
repolarization

20. U wave –Positive deviation after T wave and preceding the
next P wave

21. Look at the whole tracing.
Rhythm:Is there a P wave before each QRS complex?
−Yes: sinus rhythm No: AV junctionalor heart block
Rate: Count boxes; use caliper, ruler
PR interval: Normal -0.20 sec. or less
QRS complex: Skinny (0.10 sec. or less) or broad (BBB or
ventricular)
ST segment: Isoelectric (normal), elevated or depressed
T wave: Upright, flat or inverted
Interpretation: Normalor abnormal.
−Is the rhythmdangerous?

22. Electrocardiogram is useful in determining and
diagnosing the following…
Heart rate
Heart rhythm
Abnormal electrical conduction
Poor blood flow to heart muscle (ischemia)
Heart attack
Coronary artery disease
Hypertrophy of heart chambers.