Systematic ECG Interpretation

ECG: Systematic Analysis

Dr Nola McPherson CME SCGH 2014

ECG Interpretation Overview

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

6. QRS complex

7. ST segment

8. T wave

9. U wave

10. QT interval

ECG Interpretation Overview

11.Additional waves (D O E)

12.Chamber hypertrophy

13.Other

- T oxicology

- I schaemia

- E lectrolytes

- sudden death ECG

Q B R A D W H

- dextrocardia

- lead reversals

- artefacts

- pacing spikes

Putting it all together…Diagnosis

Differential diagnoses

Life threats

ECG Interpretation Template

1. ECG type & recording

ECG TYPE & RECORDING 12 lead vs rhythm strip

Paper rate (N= 25mm/s)

Calibration (5mm wide, 10mm high = 1mV)

Unusual leads

- right

- posterior

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

Rate, Rhythm, AxisRATE

Normal 60-100/min (tachy/bradycardia)

Method: 300/RR(large squares)

OR 1500/RR(small squares)

OR number of QRS x 6 (if 25mm/s)

RHYTHM

Pattern: regular or irregular (reg irreg or irreg irreg)

7 STEP APPROACH

Rate, Rhythm, AxisAXIS

Normal (-30 to +90)

RAD

LAD

NW axis

NORMAL SINUS RHYTHM 12 Lead ECG

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

P Wave?present or absent

Amplitude & duration (LAE/RAE/BAE)

<2.5mm amp limb leads, <1.5mm amp chest leads

<3mm duration

Contour monophasic lead II, biphasic lead V1

inverted aVR, upright I, II, V2-6

Left Atrial Enlargement

Left Atrial Enlargement

Right Atrial Enlargement

Right Atrial Enlargement

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

PR Interval Duration (N= 120-200ms)

Short (<120ms)

1. Preexcitation Syndrome

eg WPW, Lown - Ganong- Levine (LGL)

2. AV (nodal) junctional Rhythm

Long (>200ms)

1. 1 HB (alone or with other blocks)

Varying (blocks)

Short PR Interval - WPW

Short PR interval (<120ms)

Prolonged QRS (>110ms) + early slurred upstroke (delta wave)

Dominant R in V1-3

ST seg & T wave discordant changes

Short PR Interval - LGL

Short PR – AV (nodal) Junctional Rhythm

Long PR Interval

PR Segment Elevation or Depression

1. pericarditis

2. atrial ischaemia

- Liu’s Criteria

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

Q waves NORMAL

<1mm wide, <2mm deep

PATHOLOGICAL

Criteria:

- >40ms (>1mm wide)

- > 2mm deep

- >25% depth of QRS complex

- seen in lead V1- V3

DDX:

1. Myocardial infarction

2. Cardiomyopathies

Hypertrophic

Infiltrative disease

Pathological Q Waves

R wavesNORMAL

Transition point V3-V4

ABNORMAL

Dominant R wave in aVR

Dominant R wave in V1

Poor R wave progression (Ht ≤ 3 mm in V3)

Dominant R Wave in aVRCAUSES

1. Poisoning with Na channel blocking medications

(Criteria: R wave height > 3 mm, R/S ratio > 0.7)

2. Dextrocardia

3. Incorrect lead placement (L & R arms reversed)

Dominant R Wave in V1CAUSES

1. RVH (PE, L to R shunt)

2. RBBB

3. POSTERIOR MI (+ STE in leads V7,8,9)

4. WPW TYPE A

5. Hypertrophic Cardiomyopathy

6. Dextrocardia

7. Normal in children and young adults

Poor R Wave ProgressionCAUSES

1. Prior anteroseptal infarction

2. LVH

3. Dilated cardiomyopathy

4. Transpositioin of leads V1 & V3

5. May be normal

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

6. QRS complex

QRS Complex Duration

N = 70-100ms

narrow (Supraventricular)

wide (ventricular or SVT with aberrant

conduction)

Amplitude

High voltage eg LVH

Low voltage

Alternans eg pericardial effusion

Morphology

Notched

RBBB

LBBB

Spot Diagnoses

Brugada Syndrome

WPW Syndrome (delta waves)

Tricyclic poisoning (wide QRS + dom R in aVR

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

6. QRS complex

7. ST segment

ST Segment Displacement

Elevation

Depression

ST Depression Morphology

Horizontal

Up sloping

Down sloping

ST Segment Elevation

ST Segment Depression

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

6. QRS complex

7. ST segment

8. T wave

T WaveNormal

= < 5mm height in limb leads = < 15mm height in precordial leads = < 2/3 R

= <15 mm ht in precordial leads = < 2/3 R

T Wave Amplitude & Morphology

Peaked eg hyperkalaemia

Flat eg myocardial ischaemia, hypoK

Hyperacute eg early STEM, Prinzmetal angina

Inverted eg ischaemia & infarction, increased ICP

Biphasic eg Myocardial ischaemia, hypoK, Wellens

T Wave Morphology

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

6. QRS complex

7. ST segment

8. T wave

9. U wave

U Wave Normal

= 0.5 mm (max 2mm)

= 10% TW (max 25% TW)

Prominent

Inverted

U Wave Prominent

> 1-2mm or > 25% ht TW

CAUSES

Bradycardia

HypoK

HypoCa, HypoMg

Hypothermia

Increased ICP

LVH

Hypertrophic cardiomypy

Digoxin

Inverted

abnormal if in leads with upright T waves

CAUSES

Heart disease

**HIGHLY SPECIFIC FOR HEART DISEASE**

**Predicts >75% stenosis of LAD/LMCA and suggests LV dysfn**

ECG Interpretation Template

1. ECG type &recording

2. Rate, Rhythm, Axis

3. P wave

4. PR interval + segment

5. Q Waves, R waves

6. QRS complex

7. ST segment

8. T wave

9. U wave

10. QT interval

QT Interval Normal QTc

= 390-440ms M/460 ms F

< ½ preceding RR

inversely prop to HR

Measure in lead II or V5-6

Large U waves (>1 mm) fused to T included in measurement

Small, separate U waves excluded in measurement

Long (>440/460 ms)

Short (<350ms)

QT Interval

ECG Interpretation Template

11. Additional waves (D O E)

Additional Waves (D O E) Delta Wave

WPW

= slurred upstroke to QRS

Additional Features:

Short PR interval (<120ms)

Broad QRS (>100ms)

Additional Waves (D O E) Osborn Wave (J waves)

= positive deflection at J point

Most prominent in precordial leads

Causes

Hypothermia

Hyper Ca

Medications

Raised ICP

Normal varient

Additional Waves (D O E) Epsilon Wave

Arrythmogenic RV dysplasia (in 30% patients)

= pos deflection buried in end of QRS

Additional Features

TWI V1-3

Prolonged S Wave upstroke V1-3

ECG Interpretation Template

11.Additional waves (D O E)

12.Chamber hypertrophy

13. Other

- T oxicology

- I schaemia

- E lectrolytes

- sudden death ECG

- dextrocardia

- lead reversals

- artefacts

- pacing spikes

Lethal Causes SyncopeQ BRAD W H

1. QT syndrome (Long/short)

2. Brugada Syndrome

3. RV infarction

4. Arrythmogenic RV Dysplasia

5. Dilated Cardiomyopathy

6. WPW

7. Hypertrophic Cardiomyopathy

Questions & Comments

ReferencesLife in the Fast Lane ECG Library