ECG

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

einthoven's triangle :

ECG Paper ECG Speed 25mm/sec

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

Principles of ECG recording Explain the indication and the procedure for the patient. (assurance ) Ask the patient to take off any metals he/she wears. Expose the wanted sites. Cleaning of skin and shaving if necessary. Place the electrodes in the correct positions . Instruct the patient to remain still (should not talk during the test ) and relax their shoulders and legs while the recording takes place (1 min)

See video

How to comment on ECG Name.Age ,Date and time. Calibration and Speed of paper RAWIHI :

RAWIHI R: rate, regularity,rhythm(sinus or asinus), A: axis. W:waves. I :intervals. H: hypertrophy. I: ischemia

Normal Sinus Rhythm Rate = 60-100 beat / minute. The rhythm is regular All intervals are within normal limits There is a P for every QRS and a QRS for every P. P : QRS ratio = 1 : 1. The P waves all look the same Presence of P, QRS, T in each cycle. Normal shape, time of waves, segments and intervals

Interfering factors Inaccurate placement of the electrodes Electrolyte imbalances Poor contact between the skin and the electrodes Movement or muscle twitching during the test Drugs that can affect results include digitalis, quinidine, and barbiturates

MI Ischemia ( subendocardial or transmural) Injury When myocardial blood supply is abruptly reduced to a region of the heart, a sequence of injurious events occur : Ischemia ( subendocardial or transmural) Injury Necrosis, and eventual fibrosis (scarring) if the blood supply isn't restored in an appropriate period of time

Hyperacute T wave is the earliest sign of acute myocardial infarction

Precordial Septal Leads V1 – V2 – Look at the Septum of the heart – The septal branch of the LAD

Precordial Anterior Leads V3 – V4 –anterior wall of the left ventricle –The LAD diagonal branch)

Anterior-Septal Terminology

Lateral Precordial Leads I,AVL,V5 – V6 lateral of the left ventricle The left circumflex

Inferior border leads II, III and aVF the Inferior wall of the RV Posterior Descending Branch of the RCA.

Posterior MI No leads look at the posterior wall. usually associated with inferior and/or lateral wall MI. The changes of posterior myocardial infarction are seen indirectly in the anterior precordial leads. Leads V1 to V3 face the endocardial surface of the posterior wall of the left ventricle. As these leads record from the opposite side of the heart instead of directly over the infarct, the changes of posterior infarction are reversed in these leads. The R waves increase in size, becoming broader and dominant, and are associated with ST depression and upright T waves. This contrasts with the Q waves, ST segment elevation, and T wave inversion seen in acute anterior myocardial infarction. ST depression is considered reciprocal ECG changes in what should be ST elevation for acute posterior wall injury.

ECG Leads - Views of the Heart Arterial supply border lead RCA anterior Right Ventricle V3 & V4 LAD Septum V1 & V2 LCX Lateral Left Ventricle a VL,V5 & V6 inferior borderof right ventricle II+III+AVF

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