ECG Dr. Mohammed Shaat Modified by : Dr. Amal Al Maqadma.

Electrocardiography It is a voltage difference, record the electrical activity of the heart as well as valuable information about the heart function and structure. Willem Einthoven 1924

Leads (lead x electrode) LIMB LEADS I II III AVF AVL AVR CHEST LEADS V1 V2 V3 V4 V5 V6 bipolar unipolar

Limb leads

Limb leads

Both limb leads

Chest leads

What chest lead represent ?

ECG Leads - Views of the Heart V1 & V2 Septum V3 & V4 anterior +Right Ventricle V5 & V6 Lateral Left Ventricle II+III+AVF inferior border

: einthoven's triangle

ECG Paper ECG Speed 25mm/sec

12 lead ECG layout:

See video

ECG Cardiac Cycle

What is the isoelectric line؟

P wave Represent the electrical activity of both atria ( atrial depolarization) The depolarization slow within the AV node, there is a brief delay or PAUSE before the depolarization conducted to the ventricles

Normal duration <0.12 sec Absent P wave: Atrial fibrillation SA Block AV Rhythm Peak P wave: Atrial hypertrophy

PR interval Normally :0.12-0.2sec Prolonged in : heart block. Short in : W-P-W syndrome.

QRS Complex Represent the electrical activity of both ventricles. Ventricular depolarization( initiation of the ventricular contraction

QRS Complex Q wave R wave: S wave : : Normal QRS duration < 0.12 sec

QRS Complex Q wave first downward deflection . septal depolarization. 0.04sec.

R wave: first upward deflection. height: 5-8 mm. early ventricular depolarization

S wave : late ventricular depolarization,

Large QRS indicate Ventricular hypertrophy.

ST - Segment ST segment: the plateau phase of ventricular repolarization. Isoelectric or> or<1mm. If the ST segment elevated or depressed beyond the normal baseline this usually sign of serious pathology. (MI)

T- Wave T-wave :represent rapid phase of ventricular repolarization. peaked T wave: early MI hyperkalemia Black races Inverted : MI . Ventricular hypertrophy. Hypokalemia Digoxin

Q-T interval 0.4 sec in HR 70 Prolonged in : Hypocalcemia hypomagnesemia

U wave repolarization of the interventricular septum. low amplitude Prominent: suspect hypokalemia, hypercalcemia or hyperthyroidism

J wave represents the approximate end of depolarization and the beginning of repolarization camel-hump sign . Hypothermia hypocalcemia.

Low voltage ECG Obesity Emphysema COPD Severe hypothyroidism

Rate Normal heart rate 60-100/ min < 60 called bradycardia >100 called tachycardia

How To Calculate Heart Rate ?

300 No. of Large box btw R-R HR= 1500 No. of Small box btw R-R HR=

RHYTHM Look For The Distance between Identical waves. Most commonly used R-R

AXIS At any point during depolarization and repolarization electrical potential are being propagated in different directions. Most of these cancel each other out and only the net force is recorded. This net is called AXIS or cardiac VECTOR

How To Check Axis in ECG

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