An Introduction to ECG

Author : Dr.Gurumurthy M.D.

Consultant Physician

ESI Hospital, Erode

E.C.G : Electro Cardio Gram

It is a recording of the electrical activity of the heart

ECG is the only way to study and know about : -

1) Heart Blocks

2) Bundle Branch Blocks (BBB, RBB, LBB etc.)

3) Arrhythmias

4) Ischaemic Heart Diseases

No other investigations can give an idea about the above mentioned disorders.

Conducting System of the Heart : -

Site created and managed

Velsundar.K

Placement of Electrodes and Patterns of ECG Recording :-

I Hypertrophy (Thickening)

Atrial Hypertrophy : (LII, V1, V2) P - More than 2.5 x 2.5 mm

Tall P - (P-pulmonale - Right Atrium) or wide P - (P-mitrale - Left Atrium)

Ventricular Hypertrophy : (Chest Leads)

Tall R > 25mm and / or Deep S > 10 mm

II Coronary Artery Diseases (CAD)

III Arrhythmias : - Disturbances in rhythmicity

1) Sinys Rhythm :- (SA Node 70 ; A-V Node 50 ; Ventricle 30 )

Tachycardia : - Rate > 90/mt

Bradycardia : - Rate < 60/mt

2) Ectopic Rhythm : -

Ectopic - Early single Beat
Tachyarrhythmias -
Few sustained and fast
150 -250/mt

Flutter - Faster
250 - 350/mt

Fibrillation :-
Disorganised
(Reentry retrograde
retrograde conduction)

Supraventricular :- (Atrial or Nodal) Arrhythmias

Ventricular Arrhythmias :- Broad & Bizarre QRS

Escape rhythm :-

Slow and protective - fail safe mechanism (Bradycardia)

appears after a pause

Spontaneous depolarization of secondary sites
having lower intrinsic frequency of
depolarization (SA - 70 ; AV - 50 ; V - 30)
May be = Junctional escape (Narrow QRS)
Ventricular escape (Broad QRS)
Should not be suppressed

Heart Blocks :- Blocking of the conducting system

Sinus Arrest (Block) : - Sinus pause

Sick Sinus Syndrome : - Brady-Tachy Syndrome

Stoke Adam's Attack : - Fainting - No "V" activity

Nodal or Junctional Block

Complete : - Independent Atrial & Ventricular Rhythm - III degree
(Nodal Block)

Incomplete : - (Nodal delay)

Bundle Branch Block : - (BBB)
M pattern of QRS - On right chest leads (V1 to V4) - RBBB
On left chest leads (V5 to V6) - LBBB

Fascicular Block : -

Right Axis Deviation - LPFB (Left Posterior Fascicle Block)

Left Axis Deviation - LAFB (Left Anterior Fascicle Block)

Bifascicular Block - RBBB + LAFB (left anterior fascicular block)

Trifascicular Block - RBBB + LAFB + Ist degree block (prolonged PR)

(Warning) Changes to be recognised

Tachy and Brady Arrhythmias
> 5 ectopics per minute
Prolonged Q-T interval - > 0.44 → Torsade pointe

(Biphasic Ventricular Tachycardia → Ventricular Fibrillation)

Sudden changes in wave patterns. e.g. ST elevation or depression - Non Q MI
R on T → Ventricular Fibrillation
High or Low Volatage
Fresh Heart Blocks
WPW Syndrome (Wolff Parkinson White Syndrome)

→ Short PR < 0.2 sec ; Prolonged QRS > 0.11 sec : Delta wave on upstroke of R

ST - Hockey stick : inverted tick mark ; Down sloping in Digitalis toxicity
Potassium (Magnesium)
Hyperkalemia (> 5.5 mg) → flat P: Loss of ST : Symmetrical Peaked T ; Wide QRS (interventricular conduction delay) → V.F.

Hypokalaemia (< 3 mg )
Flat T ; Prominent U ; ST ?
Supraventricular Tachycardia
1st & 2nd degree Block

Hypercalcemia
Shortening of QT & ST Seg

Hypocalcemia
Prolonged QT & ST Seg

Pericarditis
No Q ; Concave upward ST

Pulmonary Embolism

S1 Q III TIII

↑ ST and ↓ T in V1 - V2 (RV)

prominent S in V5 - V6 (LV)

RBBB

Unstable Angina
(Non ST elevation MI
Acute Coronary Syndrome
Subendocardial infarction - No Q)

Pre-infarction angina

Angina at rest

20% develop MI

Usually due to left coronary Artery disease

Atrial Infarction
↑ PR Segment (P-T) in LII LIII

Posterior Wall Infarction

Prinzmetal Variant Angina
ST elevation during attack

During night and early morning

due to ↑ sympathetic activity

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