Steps in ECG interpretation

12 lead ECG interpretation

Dr. K.Ranjadayalan (Ranjan)

04/04/2018

• Indications for ECG

• Clinical significance of abnormal ECG

• Basics of ECG interpretation

Indications for ECG

Suspected Heart Failure Ankle Oedema

Breathlessness/tiredness

Chest pain (acute) Myocardial infarct / ischaemia

Pericarditis

Drug effects Cardiomyopathy

QTc prolongation

Evaluation of Abnormal pulse

Abnormal BP (High or Low)

Abnormal Heart sounds

Faint (Syncope)

ECG - Clinical Informations Arrhythmias -

Tachyarrhythmia

Bradyarrhythmia

Risk of arrhythmia –

PR interval/delta wave

QT interval

Tall T wave

Structural abnormality – Atria - dilatation

Ventricles – hypertrophy

Coronary Heart Disease Previous infarction

Acute infarction or ischaemia

Steps in ECG interpretation

The electrocardiogram

12 lead ECG -Terminology

• Limb Leads – L1, L2, L3 , aVR, aVL, aVF

• Chest leads – V1 V2, V3 V4 V5 V6

For Coronary Heart disease

Anterior Leads – L1, aVL, V1 V2, V3 V4 V5 V6

Inferior leads – L11, L111 , aVF

Lateral leads – V5, V6

10 Leads to obtain 12 Lead ECG

Step 1

• Rhythm V1 or L2

• If P and QRS one to one relationship

And

Equal PR interval

Sinus Rhythm

Sinus rhythm - SA node controls the

ventricle on a 1 :1 ratio

L11

V1

Step 2

Heart Rate V1 or L11

300

RR interval

> 100 = Sinus tachycardia

< 60 = Sinus bradycardia

Sinus tachycardia

• Myocardial disease - MI,dysfunction, myocarditis, LVF

• Pulmonary embolism

• Pneumonia or other sepsis

• Anaemia

• Thyrotoxicosis

• Drugs (salbutamol, Dobutamine, Antidepressants)

• Anxiety

Sinus bradycardia

• Medication – beta blocker or anti arrhythmic

• Hypothyroidism

• Inferior ischaemia /infarction

• Hyperkalaemia

• Physiological

Step 3 - P wave

Normal P wave

Step 3

Abnormal P waves

M shaped P in lead II

Prominent terminal negative P

wave in lead V1

Tall P wave in V1 or L11

A 59 year old lady with chronic bronchitis.

Step 4

• PR interval V1 or L11

First degree heart block

• Medication related - e.g -DTZ, Verapamil, BB

• Inferior infarction

• Physiological - High vagal tone

Step 5,6,7,8

• QRS abnormalities

Step 5. QRS duration

Step 6. Pathological Q waves

Step 7. Pathological R wave

Step 8. Pathological S wave

Step 5

• QRS duration V1

QRS duration > 0.12s or 120 msecs = BBB

LBBB

Incidence increase with age

Causes

IHD, H/T, Cardiomyopathy, Aortic valve disease

progressive conduction tissue disease, ? can be benign

Echocardiogram - essential

RBBB

Causes - IHD, H/T, Cardiomyopathy, ASD, Pulmonary embolism

??Can be normal (NOooooooooo ----------------)

Echocardiogram - Essential

1. Sinus tachycardia

2. Acute RV pressure overload can cause that well known SlQ3T3 pattern (25

%)

3. RBBB (complete or incomplete)

4. T Wave inversion in the V1 -V3 with or without tall R waves in these leads.

5. RA enlargement - P pulmonale

6. RVH

7. Atrial flutter or atrial fibrillation

ECG Changes of Pulmonary Embolism

Sinus Rhythm ECG

First 5 steps - Lead V1 or L11

Step 6

• Pathological Q waves

– Anterior Leads – L1,avL, V1 to V6

– Inferior Leads - Lead 2, Lead 3 and aVF

Pathological Q wave Pathological S wave

QRS terminology

Causes of Pathological Q waves

• Myocardial Infarction – Acute or Old

• Cardiomyopathy

Step 7

• Pathological R wave v1 v2 v3

R wave > S wave in 2 leads

RVH

Posterior MI

L11

Step 8

• Pathological S wave - v1 ,v2 , v3

If deepest S wave > 20 mm or

S in V1 + R in V5 or V6 > 35 mm

– LVH

Other Criteria for LVH

Left ventricular hypertrophy (LVH)

There are many different criteria for LVH.

Sokolow + Lyon (Am Heart J, 1949;37:161)

S V1+ R V5 or V6 > 35 mm

Cornell criteria (Circulation, 1987;3: 565-72)

SV3 + R avL> 28 mm in men

SV3 + R avL > 20 mm in women

Framingham criteria (Circulation,1990; 81:815-820)

R avL> 11mm, R V4-6 > 25mm

S V1-3 > 25 mm,

S V1 or V2 + R V5 or V6 > 35 mm.

Step 9

• ST Segment Shift

Anterior Leads – L1,avL, V1- V6

Inferior Leads - L 11, L 111 and aVF

Causes of ST Elevation

Common causes

1. Acute MI (STEMI)

2. Acute Pericarditis

3. Benign Early Depolarisation

Uncommon Causes

1. Coronary artery spasm

2. Ventricular aneurysm

3. Brugada syndrome

Step 10

• T wave changes – Inverted or Tall

Anterior Leads – L1,avL, V1- V6

Inferior Leads - L 11, L 111 and aVF

Please note - T waves upright in L1,L2, V3 – V6

Causes of T wave inversion

• Ischaemic Heart Disease – ACS or Chronic stable IHD

• LVH

• Cardiomyopathy

• Pulmonary embolism

• Digoxin effect

Angiography revealed a 100% mid-LAD occlusion, which was successfully stented.(De Winter’s T Waves)

ECG Changes of Hyperkalaemia

– Peaked T waves (usually the earliest change)

– Prolongation of PR segment

– P wave flattens and disappear

– Widening of QRS with bizarre morphology (k > 7.0)

– Sinus bradycardia

– Development of a sine wave appearance (a pre-terminal rhythm)

Step 11

• QT Interval measurement

– Should always be corrected for the heart rate

– Bazett’s formula is the most commonly used

– If Heart rate > 110 or < 60 Hodges formula is more accurate

– (QTc = QT + 1.75 (heart rate – 60)

• 1 in 2000

• L11 or V5

• Bazett’s formula - QTc

• QTc < 440 ms (men) or < 470 ms (women)

• Females are more prone to the development of torsade than males because

they have longer QTc.

55

Long QT Syndrome

QT Interval measurement

• Should always be corrected for the heart rate

• Bazett’s formula is the most commonly used

• If Heart rate > 110 or < 60 Hodges formula is more accurate

QTc = QT + 1.75 (heart rate – 60)

Long QT leading to Torsades de pointes (TDP)

Drugs causing long QT Syndromes

Antiarrhythmics – Sotalol, Amiodarone, disopyramide

Antibiotics – Erythro/Clarithromycin, Levofloxacin, Moxifloxacin

Antifungals - Ketoconazole, itraconazole

Antipsychotic - Haloperidol,pimozide,chlorproazine

Thioridazine,mesoridazine

Antihistamines - Terfenadine, astemizole

Methadone

Drugs and Long QT

• Haloperidol - intravenously or at higher doses, risk of sudden death, QT

prolongation and torsades increases

• Quetiapine is generally considered to be safe, yet overdoses with quetiapine

have been shown to cause significant QT-lengthening effects

• Prolongation of QTc interval and cardiac arrhythmia, including Torsade de

Pointes, are known risks with Ondansetron. So careful of dosage in > 75.(single

dose of intravenous ondansetron for the prevention of CINV must not exceed 8

mg - infused over at least 15 minutes

Step 12 QRS Axis deviation

Both I and aVF +ve = normal axis

Both I and aVF -ve = axis in the Northwest Territory

lead I -ve and aVF +ve = right axis deviation

lead I +ve and aVF –ve

lead II +ve = normal axis

lead II -ve = left axis deviation

Summary

12 lead ECG is required for complete and accurate interpretation

ECG interpretation - Systematic

Sinus Rhythm (12steps)

Arrhythmia ( 5 steps)

ECG is a useful screening test for Heart failure

ECG is mandatory for acute chest pain of suspected cardiac origin

In patients with recurrent chest pain normal ECG has low NPV

12 lead ECG is essential for the diagnosis and classification of arrhythmias

Is this ECG changes Life threatening ?