Posts on ECG Library – LITFL Basics

ECG Differential Diagnosis

Sun, 21 Dec 2025 00:00:00 +0000

Lists of differential diagnoses of specific ECG findings based on from ECGs for the Emergency Physician 1 and ECGs for the Emergency Physician 2

Atrial fibrillation with slow ventricular response

Severe AV nodal disease
Hypothermia
Medications: Digoxin toxicity, Calcium-channel blocker / beta-blocker toxicity

Tachydysrhythmias

Narrow-complex regular rhythm:

Narrow-complex irregular rhythm:

Wide-complex regular rhythm:

Ventricular tachycardia
Sinus tachycardia with aberrant conduction
SVT with aberrant conduction
Atrial flutter with aberrant conduction

Wide-complex irregular rhythm:

Atrial fibrillation with aberrant conduction (for example bundle branch block)
Atrial flutter with variable block and aberrant conduction
Multifocal atrial tachycardia with aberrant conduction
Atrial fibrillation with WPW
Polymorphic ventricular tachycardia / Torsades de Pointes

Leftward axis

Low voltage

Myxoedema
Large pericardial effusion
Large pleural effusion
End-stage dilated cardiomyopathy
Severe chronic obstructive pulmonary disease
Severe obesity
Infiltrative myocardial diseases (i.e. restrictive cardiomyopathy)
Constrictive pericarditis
Prior massive MI
Low gain settings on ECG machine

Increased QRS Duration

Hypothermia
Hyperkalaemia
WPW
Aberrant intraventricular conduction (for example bundle branch block)
Ventricular ectopy
Paced beats
Drugs, particularly those with sodium-channel blocking effects

Increased QT-interval (and QTc-interval)

*Hypokalemia — the actual QT-interval is normal; the QT-interval appears prolonged because of the presence of fusion of the T-wave with a U-wave (a “T-U fusion complex”)

Top 20 Online ECG Courses

Sun, 21 Dec 2025 00:00:00 +0000

Difficult to master (and even harder to teach), the area of ECG interpretation has spawned an entire learning industry devoted to the topic. We take a Google deep dive to evaluate you 20 of the the best #FOAMed and paid ECG courses available online.

ECG Course selection criteria

Inclusion criteria: The ECG course had to be

in the English language
readily accessible online, without requiring a formal application process
found within the first 50 organic Google search results for “ECG/EKG course online” including geographical permutations for UK, US, Canada, New Zealand, or Australia
a structured course providing students with a defined learning path, not just a series of references/examples and practice cases.
provide a breadth of learning from basic to advanced applicable to the majority of health care providers such nurses, paramedics, EMT, PA, physicians

Notable exclusions:

Osborn Wave (J Wave)

Mon, 21 Jul 2025 00:00:00 +0000

Osborn Wave (J Wave) Overview

The Osborn wave (J wave) is a positive deflection seen at the J point in precordial and true limb leads. It is most commonly associated with hypothermia. These changes will appear as a reciprocal, negative deflection in aVR and V1.

The J point in the ECG is the point where the QRS complex joins the ST segment. It represents the approximate end of depolarization and the beginning of repolarization as determined by the surface ECG. There is an overlap of around 10ms.

Epsilon Wave

Wed, 16 Jul 2025 00:00:00 +0000

Epsilon Wave Definition

Small deflection (“blip” or “wiggle”) buried in the end of the QRS complex
On Standard 12-lead ECG (S-ECG), best seen in ST segment of V1 and V2, they are usually present in leads V1 through V4
Caused by post-excitation of myocytes in the right ventricle
Characteristic finding in patients with arrhythmogenic right ventricular dysplasia (ARVD)

Epsilon wave in V1 due to RV conduction delay

Epsilon waves are the most specific and characteristic finding in arrhythmogenic right ventricular dysplasia (ARVD). In ARVD, myocytes are replaced by fat, producing islands of viable myocytes in a sea of fat. This causes a delay in excitation of some of the myocytes of the right ventricle, producing a small “blip” seen during the ST segment of the ECG.

Raised Intracranial Pressure

Tue, 14 Jan 2025 00:00:00 +0000

Characteristic ECG Abnormalities with Raised Intracranial Pressure

Widespread giant T-wave inversions (“cerebral T waves”)
QT prolongation
Bradycardia (the Cushing reflex – indicates imminent brainstem herniation)

Other possible ECG changes that may be seen:

ST segment elevation / depression — this may mimic myocardial ischaemia or pericarditis
Increased U wave amplitude
Other rhythm disturbances: sinus tachycardia, junctional rhythms, premature ventricular contractions, atrial fibrillation

In some cases, these ECG abnormalities may be associated with echocardiographic evidence of regional ventricular wall motion abnormality (so-called “neurogenic stunned myocardium”).

ECG in Toxicology

Wed, 18 Dec 2024 00:00:00 +0000

OVERVIEW

The ECG is important in the assessment and management of poisoned patients for:

screening
diagnosis
prognosis
monitoring progression to guide management and disposition

USE AS A SCREENING TEST

A 12-lead ECG should be performed in all deliberate self-poisoning patients

non-invasive
inexpensive
readily available
identifies occult but potentially lethal cardiac conduction abnormalities

MECHANISMS OF CARDIOTOXICTY AND THEIR MANIFESTATIONS

Fast sodium channel blockade leads to slowed phase 0 of the cardiac action potential

ECG Axis Interpretation

Sun, 17 Nov 2024 00:00:00 +0000

Cardiac axis represents the sum of depolarisation vectors generated by individual cardiac myocytes. Clinically is is reflected by the ventricular axis, and interpretation relies on determining the relationship between the QRS axis and limb leads of the ECG (below diagram)

Since the left ventricle makes up most of the heart muscle under normal circumstances, normal cardiac axis is directed downward and slightly to the left:

Normal Axis = QRS axis between -30° and +90°.

Abnormal axis deviation, indicating underlying pathology, is demonstrated by:

ECG Rate Interpretation

Sun, 17 Nov 2024 00:00:00 +0000

Understanding paper speeds

Paper output speed is the rate at which the ECG machine produces a trace
Standard output is 25mm per second
If a different paper speed is used, standard rate calculations will have to be modified appropriately (see other examples below)

The standard paper speed is 25mm/sec:

1 SMALL square (1mm) = 0.04 sec (40ms)
5 SMALL squares (5mm) = 1 LARGE square = 0.2 sec (200ms)
5 LARGE squares = 1 second

Biatrial Enlargement

Tue, 08 Oct 2024 00:00:00 +0000

To best understand ECG features of biatrial enlargement, it is recommended that you first review ECG changes seen in left atrial enlargement and right atrial enlargement.

Biatrial Enlargement Definition

Biatrial enlargement is diagnosed when criteria for both right and left atrial enlargement are present on the same ECG.
The diagnosis of biatrial enlargement requires criteria for LAE and RAE to be met in either lead II, lead V1 or a combination of leads

ECG Criteria for Biatrial Enlargement

The spectrum of P-wave changes in leads II and V1 with right, left, and biatrial enlargement is summarised below:

ECG Conduction Blocks

Tue, 08 Oct 2024 00:00:00 +0000

ECG Library summary of the different types of conduction disturbance, with links to read more about each type of conduction block

Conduction Blocks

First-degree block

First-degree block PR interval >200 msec (1 large square)

Second-degree block

Mobitz Type I (Wenckebach Block): progressive prolongation of the PR interval before the missed QRS complex
Mobitz Type II (Hay Block): absence of progressive prolongation of the PR interval before the missed QRS complex
Fixed ratio blocks (e.g. 2:1, 3:1): constant relationship between P waves and QRS complexes (e.g. 2:1 = 2 P waves for each QRS complex).
High grade AV block: 2nd degree AV block with a high P:QRS ratio, producing a very slow ventricular rate

Third-degree block

Third-degree block: absence of any relationship between P waves of sinus origin and QRS complexes (AV dissociation)

Fascicular Blocks

Left anterior fascicular block (LAFB)

Left axis deviation
qR complexes in leads I, aVL
rS complexes in leads II, III, aVF
Prolonged R wave peak time in aVL > 45ms

Left posterior fascicular block (LPFB)

Right axis deviation
rS complexes in leads I, aVL
qR complexes in leads II, III, aVF
Prolonged R wave peak time in aVF

Right bundle branch block

QRS > 120 ms
Dominant R wave in V1
RSR’ pattern (“M”) in V1 with wide, slurred S wave (“W”) in V6 (=MaRRoW)

Left bundle branch block

QRS > 120 ms
Dominant S wave in V1
Deep S wave (“W”) in V1 with broad R wave (“M”) in V6 (=WiLLiaM)

Bifascicular block

RBBB plus either LAFB or LPFB

Trifascicular block

Bifascicular block plus 3rd degree AV block

Interventricular conduction disturbance

QRS > 100 ms, not due to LBBB or RBBB. Most important causes are hyperkalaemia or tricyclic antidepressant poisoning

Advanced Reading

Online

Left Atrial Enlargement

Tue, 08 Oct 2024 00:00:00 +0000

Left Atrial Enlargement

Left atrial enlargement (LAE) is due to pressure or volume overload of the left atrium. LAE is often a precursor to atrial fibrillation.

Also known as: Left Atrial Enlargement (LAE), Left atrial hypertrophy (LAH), left atrial abnormality.

P wave changes with Left Atrial Enlargement

ECG Criteria for Left Atrial Enlargement

LAE produces a broad, bifid P wave in lead II (P mitrale) and enlarges the terminal negative portion of the P wave in V1.

Left Axis Deviation (LAD)

Tue, 08 Oct 2024 00:00:00 +0000

Left Axis Deviation LAD

Left Axis Deviation = QRS axis less than -30°.

Normal Axis = QRS axis between -30° and +90°
Right Axis Deviation = QRS axis greater than +90°
Extreme Axis Deviation = QRS axis between -90° and 180° (AKA “Northwest Axis”)

Hexaxial Reference System

Hexaxial Reference System – relationship between QRS axis and frontal leads of the ECG.

How to recognise left axis deviation

Three Lead analysis

QRS is POSITIVE (dominant R wave) in Lead I
QRS is NEGATIVE (dominant S wave) in leads II, III and aVF

Normal Sinus Rhythm

Tue, 08 Oct 2024 00:00:00 +0000

Overview of normal sinus rhythm (NSR)

The default heart rhythm
Pacemaking impulses arise from the sino-atrial node and are transmitted to the ventricles via the AV-node and His-Purkinje system
This results in a regular, narrow-complex heart rhythm at 60-100 bpm

ECG features of normal sinus rhythm

Regular rhythm at a rate of 60-100 bpm (or age-appropriate rate in children)
Each QRS complex is preceded by a normal P wave
Normal P wave axis: P waves upright in leads I and II, inverted in aVR
The PR interval remains constant
QRS complexes < 100 ms wide (unless co-existent interventricular conduction delay present)

Normal heart rates in children

Newborn: 110 – 150 bpm
2 years: 85 – 125 bpm
4 years: 75 – 115 bpm
6 years+: 60 – 100 bpm

Variations on sinus rhythm

Sinus tachycardia = sinus rhythm with resting heart rate > 100 bpm in adults, or above the normal range for age in children
Sinus bradycardia = sinus rhythm with resting heart rate < 60 bpm in adults, or below the normal range for age in children
Sinus arrhythmia = sinus rhythm with a beat-to-beat variation in the P-P interval (the time between successive P waves), producing an irregular ventricular rate

Example ECG

Pacemaker Rhythms – Normal Patterns

Tue, 08 Oct 2024 00:00:00 +0000

Pacemaker Components

1. Pulse generator

Power source
Battery
Control circuitry
Transmitter / Receiver
Reed Switch (Magnet activated switch)

2. Lead(s)

Single or multiple
Unipolar or bipolar

Pacemaker Classification

Pacemakers are classified by the nature of their pacing mode.
Classification follows pacemaker code developed by the North American Society of Pacing and Electrophysiology (NASPE) and the British Pacing and Electrophysiology Group (BPEG).
The NASPE/BPEG Generic (NBG) Pacemaker Code was last revised in 2002, although many textbooks still use the previous version from 1987.
The code is expressed as a series of up to five letters.

NBG Pacemaker Code (2002)

Q Wave

Tue, 08 Oct 2024 00:00:00 +0000

The Q Wave

A Q wave is any negative deflection that precedes an R wave

The Q wave represents the normal left-to-right depolarisation of the interventricular septum
Small ‘septal’ Q waves are typically seen in the left-sided leads (I, aVL, V5 and V6)

Q waves in context

Q waves in different leads

Small Q waves are normal in most leads
Deeper Q waves (>2 mm) may be seen in leads III and aVR as a normal variant
Under normal circumstances, Q waves are not seen in the right-sided leads (V1-3)

Pathological Q Waves

Q waves are considered pathological if:

QT Interval

Tue, 08 Oct 2024 00:00:00 +0000

Definition

Time from the start of the Q wave to the end of the T wave
Represents time taken for ventricular depolarisation and repolarisation, effectively the period of ventricular systole from ventricular isovolumetric contraction to isovolumetric relaxation

The QT interval is inversely proportional to heart rate:

The QT interval shortens at faster heart rates
The QT interval lengthens at slower heart rates
An abnormally prolonged QT is associated with an increased risk of ventricular arrhythmias, especially Torsades de Pointes
Congenital short QT syndrome has been found to be associated with an increased risk of paroxysmal atrial and ventricular fibrillation and sudden cardiac death

How to measure the QT interval

The QT interval is usually measured in either lead II or V5-6, however the lead with the longest measurement should be used
Several successive beats should be measured, with the maximum interval taken
Large U waves (> 1mm) that are fused to the T wave should be included in the measurement
Smaller U waves and those that are separate from the T wave should be excluded
The maximum slope intercept method is used to define the end of the T wave (see below)

Right Atrial Enlargement

Tue, 08 Oct 2024 00:00:00 +0000

ECG Criteria of Right Atrial Enlargement

Right atrial enlargement produces a peaked P wave (P pulmonale) with amplitude:

2.5 mm in the inferior leads (II, III and AVF)
1.5 mm in V1 and V2

Also known as: Right Atrial Enlargement (RAE), Right atrial hypertrophy (RAH), right atrial abnormality

P wave changes with Right Atrial Enlargement

Causes of Right Atrial Enlargement

The principal cause is pulmonary hypertension due to:

Sinus Arrhythmia

Tue, 08 Oct 2024 00:00:00 +0000

Sinus Arrhythmia Overview

Sinus rhythm with a beat-to-beat variation in the P-P interval (the time between successive P waves), producing an irregular ventricular rate.

Characteristics

Variation in the P-P interval of more than 120 ms (3 small boxes).
The P-P interval gradually lengthens and shortens in a cyclical fashion, usually corresponding to the phases of the respiratory cycle.
Normal sinus P waves with a constant morphology (i.e. no evidence of premature atrial contractions).
Constant P-R interval (i.e. no evidence of Mobitz I AV block).

Mechanism

Sinus arrhythmia is a normal physiological phenomenon, most commnonly seen in young, healthy people.

T wave

Tue, 08 Oct 2024 00:00:00 +0000

T wave Overview

The T wave is the positive deflection after each QRS complex. It represents ventricular repolarisation.

Normal T wave characteristics

Upright in all leads except aVR and V1
Amplitude < 5mm in limb leads, < 10mm in precordial leads (10mm males, 8mm females)
Duration relates to QT interval

T wave abnormalities

Peaked T waves
Hyperacute T waves
Inverted T waves
Biphasic T waves
‘Camel Hump’ T waves
Flattened T waves

Peaked T waves

The ST Segment

Tue, 08 Oct 2024 00:00:00 +0000

S-T Segment

The ST segment is the flat, isoelectric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave.

The ST Segment represents the interval between ventricular depolarization and repolarization.
The most important cause of ST segment abnormality (elevation or depression) is myocardial ischaemia or infarction.

Causes of ST Segment Elevation

U Wave

Tue, 08 Oct 2024 00:00:00 +0000

U wave Overview

The U wave is a small (0.5 mm) deflection immediately following the T wave

U wave is usually in the same direction as the T wave.
U wave is best seen in leads V2 and V3.

Source of the U wave

The source of the U wave is unknown. Three common theories regarding its origin are:

Delayed repolarisation of Purkinje fibres
Prolonged repolarisation of mid-myocardial “M-cells”
After-potentials resulting from mechanical forces in the ventricular wall

Features of Normal U waves

The U wave normally goes in the same direction as the T wave
U -wave size is inversely proportional to heart rate: the U wave grows bigger as the heart rate slows down
U waves generally become visible when the heart rate falls below 65 bpm
The voltage of the U wave is normally < 25% of the T-wave voltage: disproportionally large U waves are abnormal
Maximum normal amplitude of the U wave is 1-2 mm

VT versus SVT

Tue, 08 Oct 2024 00:00:00 +0000

Regular broad complex tachycardias can be ventricular (VT) or supraventricular (SVT with aberrancy) in origin, and differentiation between the two will significantly influence management of your patients.

Unfortunately, the electrocardiographic differentiation of VT from SVT with aberrancy is not always possible.

Differential diagnosis of regular broad complex tachycardia

Ventricular tachycardia (VT)
Supraventricular tachycardia (SVT) with aberrant conduction due to bundle branch block
SVT with any metabolic disturbance that slows supraventricular action potential propagation — hyperkalaemia, sodium channel blockade, severe acidosis
Antidromic AVRT — re-entrant tachyarrhythmia seen in Wolff-Parkinson-White syndrome
Accelerated idioventricular rhythm (AIVR)

ECG features increasing the likelihood of VT

Electrocardiographic features that increase the likelihood of VT include:

ECG Rhythm Evaluation

Tue, 01 Oct 2024 00:00:00 +0000

The rhythm is best analyzed by looking at a rhythm strip. On a 12 lead ECG this is usually a 10 second recording from Lead II.

Confirm or corroborate any findings in this lead by checking the other leads.
A longer rhythm strip, recorded perhaps recorded at a slower speed, may be helpful.

7 step approach to ECG rhythm analysis

1. Rate

Tachycardia or bradycardia?
Normal rate is 60-100/min.

2. Pattern of QRS complexes

Regular or irregular?
If irregular is it regularly irregular or irregularly irregular?

3. QRS morphology

Narrow complex: sinus, atrial or junctional origin.
Wide complex: ventricular origin, or supraventricular with aberrant conduction.

4. P waves

Absent: sinus arrest, atrial fibrillation
Present: morphology and PR interval may suggest sinus, atrial, junctional or even retrograde from the ventricles.

5. Relationship between P waves and QRS complexes

AV association (may be difficult to distinguish from isorhythmic dissociation)
AV dissociation
- *complete:*atrial and ventricular activity is always independent.
- incomplete: intermittent capture.

6. Onset and termination

Abrupt: suggests re-entrant process.
Gradual: suggests increased automaticity.

7. Response to vagal manoeuvres

Sinus tachycardia, ectopic atrial tachydysrhythmia: gradual slowing during the vagal manoeuvre, but resumes on cessation.
AVNRT or AVRT: abrupt termination or no response.
Atrial fibrillation and atrial flutter: gradual slowing during the manoeuvre.
VT: no response.

Differential Diagnosis

Follow links below for examples of individual rhythms.

Misplacement of V1 and V2

Wed, 15 May 2024 00:00:00 +0000

Misplacement of V1 and V2: Don’t let this mistake mess up your ECG interpretation!

The proper location of V1 and V2 have not changed in many decades. They are located in the 4th intercostal space, just right and left, respectively, of the sternum. It is fairly easy to determine this spot using the angle of Louis as a landmark.

However, V1 and V2 were being misplaced pretty much right after being invented. This error in lead positioning usually produces trivial changes in the QRS pattern in those leads, and thus no real change in ECG interpretation. But certain erroneous ECG patterns can be generated, and it is important to recognize lead misplacement as a potential cause.

QRS Interval

Mon, 14 Aug 2023 00:00:00 +0000

QRS Complex Morphology

Main features to consider:

Width of the complexes: Narrow versus broad.
Voltage (height) of the complexes.
Spot diagnoses: Specific morphology patterns that are important to recognise.

QRS Complex Naming Convention

Courtesy of ECGwaves.com

QRS Width

Normal QRS width is 70-100 ms (a duration of 110 ms is sometimes observed in healthy subjects). The QRS width is useful in determining the origin of each QRS complex (e.g. sinus, atrial, junctional or ventricular).

De Winter T Wave

Thu, 22 Jun 2023 00:00:00 +0000

First reported by Dutch Professor of Cardiology, Robbert J. de Winter in 2008, the de Winter ECG pattern is an anterior STEMI equivalent that presents without obvious ST segment elevation. These patients are suffering occlusion myocardial infarction (OMI) and require immediate reperfusion therapy.

ECG Diagnostic Criteria

Tall, prominent, symmetrical T waves in the precordial leads
Upsloping ST segment depression > 1mm at the J point in the precordial leads
Absence of ST elevation in the precordial leads
Reciprocal ST segment elevation (0.5mm – 1mm) in aVR
Typical STEMI morphology may precede or follow the De Winter pattern

VT versus SVT: It’s as easy as ABCDE

Tue, 23 May 2023 00:00:00 +0000

VT or not VT…that is the question

Most of us know this question all to well. We are also probably familiar with the long list of ECG features “suggestive” of ventricular tachycardia (VT). Unfortunately, this list is not always intuitive, and can be difficult to recall and apply under pressure on the floor.

How can we simplify things?

I’ve spent the last few days coming up with a more easily applicable approach to this common dilemma.

J point

Fri, 07 Apr 2023 00:00:00 +0000

The J point

The J point is the the junction between the termination of the QRS complex and the beginning of the ST segment.

The J (junction) point in the ECG is the point where the QRS complex joins the ST segment. It represents the approximate end of depolarization and the beginning of repolarization as determined by the surface ECG. There is an overlap of around 10ms.

The J point marks the end of the QRS complex, and is often situated above the baseline, particularly in healthy young males. The J point may deviate from the baseline in early repolarization, epicardial or endocardial ischaemia or injury, pericarditis, RBBB, LBBB, RVH, LVH or digitalis effect.

Dressler beat

Mon, 30 May 2022 00:00:00 +0000

Description

Dressler beat: Specifically a ‘ventricular fusion beat‘ in the presence of paroxysmal ventricular tachycardia. Typically observed in ECG tracings of wide complex tachycardia such as VT with AV dissociation.

Supraventricular and a ventricular impulses coincide to produce a hybrid complex which is different to the VT complex and the native complex (capture beat)

The term ‘fusion beat‘ was originally used to define any hybrid QRS complex of atria or ventricular origin. Fusion beats (and capture beats) are not ‘diagnostic‘ or ‘pathognomic‘ of VT and can occur in any arrhythmia (including SVT with aberrancy for example)

Cardiac Axis Trainer

Tue, 10 May 2022 00:00:00 +0000

Learning cardiac axis interpretation can be tedious.

I have created an open source webapp hosted on CardiacAxis.com. Here you will be able to analyse in English and German the ECG variations with axis deviation.

The Axis trainer online is interactive and the arrow can be moved to demonstrate each of the specific QRS complex changes. Bookmark to your phone homepage and try it out for yourself. Below is a quick demonstration through 360 degrees…

ECG Exam Template

Tue, 03 May 2022 00:00:00 +0000

The following headings and prompts can be used as template for ECG-based exam questions.

Amjid Rehman (@amjidrehman) has made an easy interactive online template ‘ECG made easier‘ based on the template structure outlined

ECG type and recording

12 lead vs rhythm strip, rate (normal 25 mm/s)
Calibration (5mm wide, 10mm high = 1mV)
Unusual leads – right, posterior, lead grouping format

Rate

normal 60 – 100/min
tachy/bradycardia (SA node) vs –arrhythmia (not SA node)
method: 300/RR interval (large squares) or number of QRS complexes x 6 (if 25mm/s)

ST depression does not localise

Tue, 03 May 2022 00:00:00 +0000

I have had a few people ask me about the following statement from ECG Case 121:

“The reciprocal ST depression seen in leads III and aVF (in high lateral infarction) is often mistaken for inferior ischaemia. One must recall that ST depression does not localise, and such ST depression should be assumed to be a reflection of ST elevation in mirror image leads.”

Buttner, Aslanger: ECG Case 121

“ST depression does not localise” – what does this mean?

The term “localise” has two relevant interpretations here.

Delta Wave

Thu, 10 Feb 2022 00:00:00 +0000

Delta Wave Overview

The Delta wave is a slurred upstroke in the QRS complex. It relates to pre-excitation of the ventricles, and therefore often causes an associated shortening of the PR interval. It is most commonly associated with pre-excitation syndromes such as WPW.

The characteristic ECG findings in Wolff-Parkinson-White syndrome are:

Short PR interval (< 120ms)
Broad QRS (> 100ms)
A slurred upstroke to the QRS complex (the delta wave)

ECG Lead positioning

Sun, 30 Jan 2022 00:00:00 +0000

The ECG is one of the most useful investigations in medicine. Electrodes attached to the chest and/or limbs record small voltage changes as potential difference, which is transposed into a visual tracing

Basic landmarks

3-electrode system

Uses 3 electrodes (RA, LA and LL)
Monitor displays the bipolar leads (I, II and III)
To get best results – Place electrodes on the chest wall equidistant from the heart (rather than the specific limbs)

P wave

Sat, 29 Jan 2022 00:00:00 +0000

P Wave Overview

The P wave is the first positive deflection on the ECG and represents atrial depolarisation.

The P wave is the first positive deflection on the ECG
It represents atrial depolarisation
Normal duration: < 0.12 s (< 120ms or 3 small squares)

Characteristics of the Normal Sinus P Wave

Morphology

Smooth contour
Monophasic in lead II
Biphasic in V1

Axis

MI Localization

Thu, 14 Oct 2021 00:00:00 +0000

ECG Library Homepage

Related Topics

Advanced Reading

Online

Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
Rawshani A. Clinical ECG Interpretation ECG Waves
Smith SW. Dr Smith’s ECG blog.
Wiesbauer F. Little Black Book of ECG Secrets. Medmastery PDF

Textbooks

ECG Interpretation: Other cardiac conditions

Wed, 16 Jun 2021 00:00:00 +0000

Part five of a 5 part lecture series on ECG/EKG Interpretation with Dr Theo Sklavos and cardiologist A/Prof William Wang. This lecture series is aimed primarily at medical/nursing/paramedicine students and junior trainees, but will hopefully be useful as a refresher course for those with previous experience.

Other cardiac conditions

Hyperkalemia, hypokalemia
Pericarditis, pericardial effusion
Pulmonary embolism
Long QT syndrome

ECG Interpretation lectures

References and further reading

ECG LIBRARY

ECG Interpretation: The Basics

Wed, 16 Jun 2021 00:00:00 +0000

Part one of a 5 part lecture series on the basics of ECG/EKG Interpretation with Dr Theo Sklavos and cardiologist A/Prof William Wang. This lecture series is aimed primarily at medical/nursing/paramedicine students and junior trainees, but will hopefully be useful as a refresher course for those with previous experience.

The Basics

In this first video we walk you through every aspect of the basics of the ECG including:

Describe the parts of the ECG
Rate, rhythm, axis
P wave, PR interval, QRS complex, ST-segment, T wave, QT interval
Identify the features of a normal ECG

ECG Interpretation lectures

References and further reading

ECG LIBRARY

Developing Visual Expertise in ECG Interpretation

Sun, 21 Mar 2021 00:00:00 +0000

Evaluating the Differences in Approach to the ECG Between Experts and Novices

We know that emergency medicine attendings are generally faster and more accurate at ECG interpretation than residents and medical students. But how are they able to process this information so much quicker while maintaining accuracy? And can we use these strategies to help learners progress to their own ‘expert-like’ level?

Our study combined eye-tracking and interview data to come up with a few ways in which EM attendings look and think about ECGs differently than more novice learners.1

PR Interval

Thu, 04 Feb 2021 00:00:00 +0000

↪ ECG Basics Homepage

PR Interval

The PR interval is the time from the onset of the P wave to the start of the QRS complex. It reflects conduction through the AV node.

The normal PR interval is between 120 – 200 ms (0.12-0.20s) in duration (three to five small squares).
If the PR interval is > 200 ms, first degree heart block is said to be present.
PR interval < 120 ms suggests pre-excitation (the presence of an accessory pathway between the atria and ventricles) or AV nodal (junctional) rhythm.

PR segment

Thu, 04 Feb 2021 00:00:00 +0000

↪ ECG Basics Homepage

The PR segment is the flat, usually isoelectric segment between the end of the P wave and the start of the QRS complex.

PR segment abnormalities

These occur in two main conditions:

Pericarditis
Atrial ischaemia

Pericarditis

The characteristic changes of acute pericarditis are:

PR segment depression.
Widespread concave (‘saddle-shaped’) ST elevation.
Reciprocal ST depression and PR elevation in aVR and V1
Absence of reciprocal ST depression elsewhere.

NB. PR segment changes are relative to the baseline formed by the T-P segment.

R wave

Thu, 04 Feb 2021 00:00:00 +0000

↪ ECG Basics Homepage

R wave Overview

The R wave is the first upward deflection after the P wave. The R wave represents early ventricular depolarisation

Abnormalities of the R wave

There are three key R wave abnormalities:

Dominant R wave in V1
Dominant R wave in aVR
Poor R wave progression

1. Dominant R wave in V1

Causes of Dominant R wave in V1

Normal in children and young adults
Right Ventricular Hypertrophy (RVH)
- Pulmonary Embolus
- Persistence of infantile pattern
- Left to right shunt
Right Bundle Branch Block (RBBB)
Posterior Myocardial Infarction (ST elevation in Leads V7, V8, V9)
Wolff-Parkinson-White (WPW) Type A
Incorrect lead placement (e.g. V1 and V3 reversed)
Dextrocardia
Hypertrophic cardiomyopathy
Dystrophy
- Myotonic dystrophy
- Duchenne Muscular dystrophy

Examples of Dominant R wave in V1

Normal paediatric ECG (2 yr old)

ECG Rule of Fours

Wed, 23 Dec 2020 00:00:00 +0000

aka ECG Interpretation Made Easy

One day, in a town not too far from here, the ICU registrar (you) is admitting a 60 year old male, who has just been brought into the emergency department with profound weakness, and needed to be intubated for respiratory failure. They were struggling in the ER, all resuscitation bays were full, and ambulances are backing up outside. No lab tests are back and they hadn’t even done an ECG. You sigh, and agree to take the patient against your better judgement…

ECG Interpretation: Conduction disease

Tue, 03 Nov 2020 00:00:00 +0000

Part three of a 5 part lecture series on ECG/EKG Interpretation on conduction disease with Dr Theo Sklavos and cardiologist A/Prof William Wang. This lecture series is aimed primarily at medical/nursing/paramedicine students and junior trainees, but will hopefully be useful as a refresher course for those with previous experience.

Conduction disease

Identify AV nodal block, bundle branch and fascicular blocks.
Identify escape rhythms and their origin.

ECG Interpretation lectures

References and further reading

ECG LIBRARY

ECG Interpretation: Myocardial ischaemia and infarction

Tue, 03 Nov 2020 00:00:00 +0000

Part two of a 5 part lecture series on ECG/EKG Interpretation – Myocardial ischemia and infarction – with Dr Theo Sklavos and cardiologist A/Prof William Wang. This lecture series is aimed primarily at medical/nursing/paramedicine students and junior trainees, but will hopefully be useful as a refresher course for the more experienced.

Myocardial ischaemia and infarction

Identify the signs of myocardial ischaemia on the ECG.
Identify which region of myocardium is ischaemic.
Identify posterior infarction, right ventricular infarction, ischaemia in paced rhythms and LBBB.

ECG Interpretation lectures

References and further reading

ECG LIBRARY

ECG Interpretation: Tachyarrhythmias

Tue, 03 Nov 2020 00:00:00 +0000

Part four of a 5 part lecture series on ECG/EKG Interpretation on tachyarrhythmias with Dr Theo Sklavos and cardiologist A/Prof William Wang. This lecture series is aimed primarily at medical/nursing/paramedicine students and junior trainees, but will hopefully be useful as a refresher course for the more experienced.

Tachyarrhythmia

Identify the common types of tachycardia. Split into wide vs narrow complex.

ECG Interpretation lectures

References and further reading

ECG LIBRARY

Super Axis Man SAM

Tue, 03 Nov 2020 00:00:00 +0000

↪ ECG Basics Homepage

Who is SAM?

As a routine part of ECG analysis, we need to determine the ECG AXIS. It isn’t really enough to just whimper… “Is it normal?” So, to help understand axis a tiny bit…I need to introduce you to SAM – the Super Axis Man

Building SAM – the Super Axis Man

(1) Draw a circle and put SAMs head on the top.

Note: SAM is smiling today because he is learning something…