ECGs Flashcards
How would you approach an ECG?
1) Check Patient ID
2) Rate - Regular = 300/Large Squares; Tachy = 1500/Small Squares; Irregular = R waves x 6
3) Rhythm - P Waves (Check Leads II, V1 & V2)
4) Axis - Upwards/Downwards (Check QRS in Leads I - III; RAD = ↓ In I;LAD = ↓ In II & III)
5) QRS Complexes - Widening = > 3 Small Sqs.
6) ST Segment (Horizontal & Isoelectric; Elevation/Depression/Strain with LVH)
7) Q-T Interval (2 large squares)
8) T Waves (Normal Inversion = V1/V2, aVR & III - not V2 alone; Abnormal Inversion = I, II & V4-V6)
Resources
https: //litfl.com/ecg-rhythm-evaluation/
https: //www.youtube.com/watch?v=ENyBhCJ2llY
https: //learning.bmj.com/learning/course-intro/ecg-skills.html?courseId=10046609&locale=en_GB
How is HR calculated?
25 mm/s
Each small square is 0.04s
Each large square is 0.2s - 5 large squares = 1s
6x Number of R waves will give rate or 300/R-R Interval
If more rapid then divide by 1500
< 60 = Bradycardia
> 100 = Tachycardia
How is Rhythm Calculated?
Heart Rhythm
Check for electrical activity
Assess P waves: check leads II, V1 & V2 also
Check Sinus Rhythm via PR Interval: PR Interval ~ 3-5 Small Squares
Check Sinus Rhythm - P wave precedes QRS complex; Normal P-R Interval; Constant P-R Interval
Check QRS is regular/irregular or narrow/broad.
Is QRS Regular or irregular?
If irregular is it regularly irregular or irregularly irregular?
Types of Sinus Rhythm
Sinus Tachycardia = > 100 beats/min
Sinus Bradycardia = < 60 beats/min
Sinus Arrhythmia = normal variation in HR with respiration (increase on inspiration)
REGULAR rhythms
Rate = 300 / number of LARGE squares between consecutive R waves
Very FAST rhythms:
Rate = 1500 / number of SMALL squares between consecutive R waves.
SLOW or IRREGULAR rhythms:
Rate = Number of R waves X 6
The number of complexes (count R waves) on the rhythm strip gives the average rate over a ten-second period. This is multiplied by 6 (10 seconds x 6 = 1 minute) to give the average Beats per minute (bpm)
Describe P Waves and their Characteristics (including duration)
Represents atrial depolarisation
Assess in Leads II, V1 & V2
P waves should be upright in leads I and II, inverted in aVR
Duration: < 0.12 s (<120ms or 3 small squares wide and 2.5 squares tall)
Atrial abnormalities are most easily seen in the inferior leads (II, III and aVF) and lead V1, as the P waves are most prominent in these leads.
Abnormal = P Pulmonale (Peaked) = Tall, Peaked P Waves (R. Atrial Enlargement)
OR P Mitrale (look like M) = Wide Bifid P Waves (Mitral Stenosis)
https://litfl.com/p-wave-ecg-library/
Describe the PR Interval and its characteristics (including duration)
Measured from the start of Atrial depolarisation (P wave) to the start of Ventricular depolarisation (Q wave)
Represents delay at AV node, protects ventricles and allows for ventricular filling
Normal = 120-200ms (3-5 small squares)
Abnormal = >200ms Heart Block (1st Degree, Mobitz 12nd Degree with prolonged PR)
https://litfl.com/pr-interval-ecg-library/
Describe the QRS Complex
Normal = <120ms (3 small squares)
Abnormal = Narrow or Broad Complex or Aberrant conduction i.e. LBBB/RBBB
Narrow complexes (QRS < 120 ms/3 small squares) are Supraventricular (above AV node) in origin.
Broad complexes (QRS > 120 ms/3 small squares) may be either ventricular in origin, OR due to aberrant conduction of supraventricular complexes (e.g. due to bundle branch block, hyperkalaemia or sodium-channel blockade).
R wave progression - R waves should increase in amplitude from V1 to V6.
Describe the QT Interval
Measured from the start of the QRS until the end of the T wave at Lead II or V5-6.
Represents ventricular repolarisation
Calculated by the Bazett formula: QTC = QT / √ RR
Abnormal = Torsades de Pointes
Describe the characteristics of the T wave
Upright in all leads except aVR and V1
Amplitude < 5mm in limb leads, < 10mm in precordial leads (10mm in men, 8mm in women)
Abnormal = Peaked, Hyperacute, Inverted T waves, Biphasic T waves, ‘Camel Hump’ T waves, Flattened T waves.
Describe how the Cardiac Axis is Calculated
Assess QRS Complexes in Leads I & avf
Normal = +ve in I and avf
Left Axis Deviation (LAD -30 to 180) = Lead I +ve and Lead avF -ve.
Right Axis Deviation (RAD +90 to +180) = Lead I -ve and Lead avF +ve.
Indeterminate axis = Lead I -ve and avF -ve.
LAD indicative of LVH or MI.
RAD indicative of RVH, PE or MI.
List Causes of RAD
Right ventricular hypertrophy
Acute right ventricular strain, e.g. due to pulmonary embolism
Lateral STEMI
Chronic lung disease, e.g. COPD
Hyperkalaemia
Sodium-channel blockade, e.g. TCA poisoning
Wolff-Parkinson-White syndrome
Dextrocardia
Ventricular ectopy
Secundum ASD – rSR’ pattern
Normal paediatric ECG
Left posterior fascicular block – diagnosis of exclusion
Vertically orientated heart – tall, thin patient
List causes of LAD
Left ventricular hypertrophy
Left bundle branch block
Inferior MI
Ventricular pacing /ectopy
Wolff-Parkinson-White Syndrome
Primum ASD – rSR’ pattern
Left anterior fascicular block – diagnosis of exclusion
Horizontally orientated heart – short, squat patient
What does the following rhythm show?
Sinus Rhythm
Normal ventricular contraction
Atrial contraction initiated by SA node depolarisation
P wave for every QRS complex
AP is propagated through AV node to ventricle after ‘delay’ of <200ms (PR <200ms)
What does the following rhythm show and how would you treat?
Sinus Arrhythmia
ECG meets all criteria of sinus rhythm but the rhythm is irregular (R-R interval)
Irregularity caused by physiological changes in the cardiac timing caused by respiration
Considered to be a normal variant
P wave for every QRS complex
No treatment required
What does the following rhythm show and describe its treatment?
Atrial Fibrillation
Disorganised electrical activity in the atria (impulses no longer travel from SA to AV node). AV node receives continuing electrical impulses and conducts some of these to the ventricle. Can occur at any ventricular rate (anywhere between 30 - 200 bpm)
Characterised by: Irregularly Irregular. No P Waves, Irregular QRS Complex (R-R intervals) and Ragged Baseline
Treatment:
https://litfl.com/atrial-fibrillation-ecg-library/
What does the following rhythm show and describe its treatment?
A regular, usually narrow-complex (QRS <120ms/3 small squares) tachycardia
Caused by a re-entry circuit within the atria, resulting in an atrial rate of 300 bpm.
Characterised by: ‘Saw-Tooth’ Baseline appearance (lead V1 or Lead II, III and aVF), Ventricular Rate is a division of 300 (3F:1 QRS ratio or variable) and F Waves.
Treatment:
https://litfl.com/atrial-flutter-ecg-library/
What does the following rhythm show and describe its treatment?
Junctional Rhythm
Originates at the AV junction instead of SA node, therefore electrical impulse travels to atria and ventricles simultaneously. Rate may be normal, bradycardic or tachycardic.
Characteristics: Regular Rhythm. Retrograde (inverted) P waves can be seen in the ST segment (seen as negative deflection) with narrow QRS-Complex unless co-existing LBBB/RBBB.
Treatment:
https://litfl.com/junctional-escape-rhythm-ecg-library/
What does the following rhythm show and describe its treatment?
Originates above or involves the AV node. Exclude Sinus, Atrial Fibrillation and Atrial Flutter. Generally involves an accessory pathway i.e. WPW. No obvious flutter waves.
Characteristics: Regular, Narrow-Complex (QRS <120ms/3 small squares) Tachycardia. Often no clear P Waves. Notch on ST-Segment (retrograde p-wave).
Treatment:
https://litfl.com/supraventricular-tachycardia-svt-ecg-library/
What does the following rhythm show and describe its treatment?
Supraventricular Ectopics
Sinus rhythm. Differing morphologies of P waves on beats 3, 6 and 9.
Characteristics: Regular, Early P waves on beat 3, 6 and 9, Narrow QRS Complex (<120ms/3 small squares). Varying PR and R-R intervals.
What does the following rhythm show and describe its treatment?
Ventricular Premature Complexes (VPCs) - Trigeminy
A premature beat arising from an ectopic focus within the ventricles.
Characteristics: Broad QRS complex (≥ 120 ms) with abnormal morphology. Unifocal — Arising from a single ectopic focus; each PVC is identical or Multifocal — Arising from two or more ectopic foci; multiple abnormal QRS morphologies.
Features:
Broad QRS complex (≥ 120 ms) with abnormal morphology.
Premature — i.e. occurs earlier than would be expected for the next sinus impulse.
Discordant ST segment and T wave changes.
Usually followed by a full compensatory pause.
Retrograde capture of the atria may or may not occur.
What does the following rhythm show and describe its treatment?
VPC: Bigeminy - ‘ectopics’, ‘VPB’, ‘PVC’ - may be a normal finding. Characterised by: 1 sinus beat coupled with a VPC.
https://litfl.com/premature-ventricular-complex-pvc-ecg-library/
What does the following rhythm show and describe its treatment?
Ventricular Tachycardia
Monomorphic: Most common form. Regular broad-complex tachycardia (QRS >120ms/3 small squares). May be associated with haemodynamic compromise. Always abnormal and must be acted upon.
https://litfl.com/ventricular-tachycardia-monomorphic-ecg-library/
What does the following rhythm show and describe its treatment?
Ventricular Tachycardia
Polymorphic: Regular broad-complex tachycardia (QRS >120ms/3 small squares). Looks like Forth Rail Bridge. Torsades de pointes - twisting around the point. May be difficult to distinguish from VF. Often associated with long-QT interval and ‘R’ on ‘T’ phenomenon.
What does the following rhythm show and describe its treatment?
Ventricular Fibrillation
Characteristics: Irregular Random baseline. No clear discernable waveforms. Chaotic irregular deflections of varying amplitude. Rate 150 to 500 bpm.
No identifiable P waves, QRS complexes, or T waves. May be subtle.
Always associated with LOC
Treatment: DC Cardioversion
What does the following rhythm show and describe its treatment?
Capture and Fusion Beats
Capture beat occurs when a sinus beat is conducted through the AV node.
Early narrow complex beat. Fusion beats are fusion between the sinus beat and next VT beat. Both are proof of independent rhythms in the atria and ventricles. Capture and Fusion beats are almost always diagnostic of VT.
What does the following rhythm show, describe its treatment
1st Degree HB
Characteristics: PR Interval prolonged (>200ms/1 large square) but constant - no progressive lengthening. Stable rhythm. No haemodynamic disturbance.
No specific treatment required
Causes: Increased vagal tone, Athletic training, Myocarditis, Normal Variant.
What does the following rhythm show, describe its treatment
2nd Degree HB - Mobitz I (Wenckebach Phenomenon)
Characteristics: Progressive PR Interval prolongation (>200ms/1 large square). Cyclical. 1st PR Normal. PR then lengthens. Eventually P wave with No QRS Complex i.e. Eventual ‘Missed Beat’ - ‘Drops a beat’.
Due to time taken for the AV node to repolarise in order to ‘accept’ the next impulse.
May be a normal variant, especially with high vagal tone (athletes).
Not treated unless severe or accompanied with collapse/haemodynamic compromise.
Causes: Drugs (BBs, CCBs, Digoxin, Amiodarone)
Treatment: Asymptomatic patients do not require treatment. Symptomatic patients usually respond to atropine. Permanent pacing is rarely required.
What does the following rhythm show, describe its treatment
2nd Degree HB - Mobitz II (Hay)
Characteristics: PR Constant. P Wave with No QRS Complex. Subsequent missed beat/QRS.
Failure of conduction at the level of the His-Purkinje system (i.e. below the AV node). May deteriorate into CHB/Asystole.
Causes: Structural damage to the conducting system (e.g. infarction, fibrosis, necrosis).
Treatment: Immediate admission for cardiac monitoring, backup temporary pacing and ultimately insertion of a permanent pacemaker.
https://litfl.com/av-block-2nd-degree-mobitz-ii-hay-block/
What does the following rhythm show, describe its treatment
3rd Degree HB (Complete HB/AV Block)
No functioning electrical connection between Atria & Ventricles. Complete absence of AV conduction – none of the supraventricular impulses are conducted to the ventricles.
P Waves & QRS Complexes Present.
Characteristics: No relationship between P wave and QRS complex. Broad QRS Complex (>120ms/3 small squares) - ventricular escape* rhythm. Typically the patient will have severe bradycardia with independent atrial and ventricular rates, i.e. AV dissociation.
Tip: Mark P Wave Positions, Move along to QRS - P Waves & QRS will be dissociated
Treatment: They require urgent admission for cardiac monitoring, backup temporary pacing and usually insertion of a permanent pacemaker. In the event of circulatory collapse with complete HB, IV Atropine and Isoprenaline may be indicated as stabilising measures until trans venous pacing wire insertion can be undertaken.
https://litfl.com/av-block-3rd-degree-complete-heart-block/
*Occurs at 30-40bpm and is broad, regular and dissociated from atrial activity. Junctional and ventricular escape rhythms arise when the rate of supraventricular impulses arriving at the AV node or ventricle is less than the intrinsic rate of the ectopic pacemaker. https://litfl.com/junctional-escape-rhythm-ecg-library/
What does the following rhythm show, describe its treatment
Pulseless Electrical Activity
Cardiac Arrest occurring with any rhythm which would usually be associated with a pulse is termed pulseless electrical activity.
Treatment: Prompt CPR is indicated and identification of a potential reversible cause.
https://litfl.com/pulseless-electrical-activity/
Describe the ECG Vascular Territories
Anterior/Anteroseptal - V1-V4; LAD
Inferior - II, III & aVF; RCA
Anterolateral - I, aVL, V4-V6; LAD/LCX
Lateral - I, aVL +/- V5-V6; LCX
Posterior - Tall R Waves V1-V2; LCX/RCA
