Steps in 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
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
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
Abnormal P waves
M shaped P in lead II
Prominent terminal negative P
wave in lead V1
Tall P wave in 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
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
Step 6
• Pathological Q waves
– Anterior Leads – L1,avL, V1 to V6
– Inferior Leads - Lead 2, Lead 3 and aVF
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.
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
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)
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