Basics of ECG interpretation

BYUSAMA ELSAYED

Lecturer of anesthesia and intensive care

Objectives Why ECG?

How to monitor ECG

Physiology of pulse conduction

Interpretation

WHY?Chest pain

Heart failure

Collapse / syncope

Shock / hypotension

Palpitations

Cardiac arrest

preoperative

GOLDEN RULE

Look at the patient

not just the paper

How ? 3-lead monitoring

12-lead monitoring

‘Quick-look’ paddles

Hands-free adhesive pads

12 lead monitoring

6 chest electrodes Called V1-6

4 limb electrodes

Right arm RideLeft arm YourLeft leg Green Right leg B ike

Sinoatrial node

AV node

Bundle of His

Bundle Branches

Purkinje f ibers

Normal Impulse Conduction

Impulse Conduction & the ECG

ECG Paper

ECG Leads

ECG waves components P wave = atrial depolarisation

QRS = ventricular depolarisation

T = repolarisation of the ventricles

ECG interpretation

History

QRS Rhythm QRS Rate QRS Width QRS Axis

P Wave P & QRS Relation Ischemic changes

History Again: treat the patient not the paper Check o Name and age o Time and date o Indication (chest pain or routine pre op) o Any previous or subsequent ECGs (Is it

part of a serial ECG sequence?)

IIII

QRS Rhythm

QRS Rhythm Sinus Rhythm Cardiac impulse originates from the sinusnode. Every QRS must be preceded by P

wave ????

Sinus not normal sinus ??

2- QRS

RATE

* At standard paper speed of 25 mm sec-1, 5 large squares = 1 second* At standard paper speed of 25 mm sec-1, 5 large squares = 1 second

QRS Width The width of the QRS complex should

be less than 0.12 seconds (3 small squares)

suggests a ventricular conduction problem usually right or left bundle branch block (RBBB or LBBB)

QRS

WIDTH

LBBB

RBBB

02/20/15Dr Gamal Abbas

NOV 2007 24

02/20/15Dr Gamal Abbas

NOV 2007 25

QRS Height

RVH: V1 R/S ratio >1 or V6 S/R ratio >1.

LVH: S in V1 or V2 + R in V5 or V6 ≥ 35 mm

The QRS Axis Represents the overall direction of the heart’s activity

Axis of –30 to +90 degrees is normal

The QRS Axis Left axis deviation(LAD)

o Inferior MI

o LVH

o Left anterior hemiblock

The QRS Axis Right axis deviation(RAD)o RVH

o Anterolateral MI

o Left posterior hemiblock

P Wave

P WaveAtrial activity

Positive in II

Negative in aVR

Height A tall P wave (over 2.5mm) can be called P

pulmonale As in right atrial enlargemento Pul. Htno TSo PS

P Wave Length> 2.5 small squares and a bifid shape is

called P mitrale Left atrial hypertrophy

o Mitral valve disease

o LVH

P & QRS Relationship 2 Questions

o Is every P followed by QRS?

o PR Interval

The PR interval measured between the start of the P

wave to the start of the QRS complex.

time between depolarisation of the atria and ventricular depolarisation.

3- 5 small squares(0.12 - 0.2 sec)

Relation between atrial and ventricular activity

Heart Block: First Degree

first degree ht block

Möbitz Type I (Wenckebach) Block

Möbitz Type II Block

Relation between atrial and ventricular activity

Heart Block: Third Degree

Relation between atrial and ventricular activity

The ST segment , T and Q wave (Ischrmic changes) ST segment Sit on the isoelectric

line Abnormal if there is planar (i.e.

flat) elevation or depression of the ST segment

The ST segment , T and Q wave (Ischrmic changes)

Baseline

The ST segment , T and Q wave (Ischrmic changes)

Width of Q wave is 0.04 secs

Peaked T wave as in hyper kalemid

I and AVL

II, III and AVF

V3 & v4

V1 & v2

V5 & v6Where the positive electrode is positioned, determines what part of the heart is seen!

A Normal 12 Lead ECG

Putting it ALL together

Anterolateral myocardial infarction

Inferior myocardial infarctionInferior myocardial infarction

Posterior myocardial infarctionPosterior myocardial infarction

Practice QRS rhythm QRS rate QRS Width P wave P & QRS relationship Ischemic changes

Let’s Practice

PracticeSupraventricular Tachycardia

Atrial Fibrillation

Atrial Flutter ( 2/1 )

Sinus Bradycardia

Practice First degree heart block

Second degree heart block (Mobits type I)

Third degree heart block

Second degree heart block (Mobits type II)

Practice

Anterior MI with lateral involvementST elevations V2, V3, V4 ST elevations II, AVL, V5

Practice

Anteroseptal MIST elevations V1, V2, V3, V4

Practice

Inferior MIST elevation II,III AVF

Practice

Inferior lateral MIST elevations II, III, AVFST elevations V5

Practice

•Acute inferior MI•Lateral ischemia

Normal

RBB w/inferior MI

Atrial fibrillation

Normal

Ventricular tachycardia

Normal

Right bundle branch block.

Lateral MI

Reciprocal changes

Common Dangerous Rhythms

Asystol

P wave Asystol

Course Ventricular Fibrillations

Fine Ventricular Fibrillations

Criteria of ventricular fibrillations* Bizarre irregular waveform * No recognisable QRS complexes

* Random frequency and amplitude

Common Dangerous Rhythms (Ventricular)

Ventricular Tachycardia

Torsade De Pointes

Any questions

Remember

Practice makes perfect .