ECG By Cameron McCloskey Flashcards
How many large squares pass through per minue on an ECG?
300
What is a normal PR length?
0.12-0.2 seconds
What is a normal QRS length?
0.08-0.12 seconds
What is a normal QT interal length?
0.35-0.43 seconds
What may cause a prolonged QT interal?
Drugs
Electrolyte abnormalities (hypokalaemia, hypocalcaemia etc.)
What can cause deviation in the QRS complex?
Venticular hypertrophy (either left or right)
Deviation in the QRS complex is best seen in which leads?
I, II and III
Which distinctive patterns will be present on the ECG for right axis deviation?
- Increases in lead III QRS
- Negative deflection in lead I QRS
The right ventricle now has more influence on the QRS than the left
Which conditions are likely to cause right axis deviation and why? copd
Pulmonary conditions
e.g. PE
These put strain on the right side of the heart so lead to hypertrophy
How does left axis deviation present on an ECG?
Negative QRS complex in lead III
Negative QRS complex in lead II
What causes left axis deviation? 2
LVH or a conduction defect
Which area of the heart do leads V1 and V2 “look” at and which pattern do they nrmally observe?
Right ventricle
- Small upward deflection (R wave - septum depolarised)
- Large downward deflection (Q wave - main muscle mass depolarised)
Which area of the heart do leads V5 and V6 “look” at and which pattern do they nrmally observe?
Left ventricle
- Small initial downward deflection (septal Q wave)
- Large upward deflection (R wave - main muscle mass depolarised)
How is it possible to tell on an ECG where the interventricular septum is present?
When R and S waves are roughly equal
That happens around V3/4
How is an ECG reported on? (6)
- Verify patient details
- Check date and time of ECG
- Check paper calibration
- Determine axis
- Look at rhythm strip for: Electrical activity, rhythm, P waves, PR interval, is each P wave followed by a QRS complex, is the QRS of normal duration
- Look at individual leads for volatge criteria changes or ST or T wave changes
what is QUADRANT METHOD ? 4
E
How to calculate HR on an ECG
How to determine the type of acut coronary syndrome
How to determine the type of acut coronary syndrome
- P wave
- PR Segmen
- PR Interva
- QRS complex
- ST Segment -the flat line between S and T
- T wave
- QT Interval- At the start of the Q wave to the end of T wave
- Atrial depolarization (From the SA node spreads throughout the atria)
- Period where all the electrical activity from SA node converge and come to the AV node, which holds on to it and manifests as an isoelectric line
- Time from when SA node fires > AV node depolarization > getting ready to send action potentials down to ventricles
- Time from when SA node fires > AV node depolarization > getting ready to send action potentials down to ventricles
- Ventricular depolarization But no net electrical activity in any direction, ventricles are just holding on to it
- Ventricular repolarization
- Time period right before the Q wave starts (ventricular depolarization) up until the end of T wave (ventricular repolarization)
- RV
- Basal septum
- Anterior wall of the heart
- High lateral wall of the LV
- Inferior wall of the hear
- aVR and V1-V3
- aVR and V2-V3
- V2-V4
- Lead I, avL and V5-V6
- Lead II, III, avF
What are the steps for reading ECG
- Rhythm o R-R interval constant? It’s regular. o R-R interval NOT constant? It’s irregular
- Rate Too Fast >100 = Tachycardia Too Slow <60 = Bradycardia Normal 60-100 = Normal R-Waves x 6 • Look at the rhythm strip • Count how many R waves x 6 • Ex above: 9 R waves x 6 = 56 bpm
- (iv) QRS o <0.12 seconds or 3 small boxes = Narrow o >0.12 seconds or 3 small boxes = Wide
- Sinus P-waves present? 0 Is P wave present Upright P-wave in Lead II? Inverted P-wave in Lead aVR? Every P followed by QRS?
- P-R Interval (block) o Time: <0.2 seconds = Normal >0.2 seconds = Prolonged Constant Variable Progressively Longer
- Narrow + Regular S
- Narrow + Irregular
- Wide + Regular
- Wide + Irregular
- Sinus Tachycardia Upright P waves in Lead III Inverted P-wave in Lead aVR Every P followed by QRS. 2:1 Atrial Flutter Supraventricular tachycardia.
- Atrial fibrillation (most common) Variable A-flutter Multifocal atrial tachycardia
- Ventricular tachycardia, until proven otherwise Supraventricular tachycardia with Bundle branch block Sinus tachycardia with Bundle branch block Antidromic WPW
- Polymorphic Supraventricular tachycardia Atrial fibrillation with WPW Atrial fibrillation with Bundle branch block
When is it called ST elevation
• 1 mm in any 2 contiguous leads except V2-V3 true ST segment elevation • 2 mm in V2-V3 true ST segment elevation
When is it ST depression and what cause it ?
≥ 0.5 mm in any 2 contiguous leads true ST depression o Horizontal ST depression: most concerning for ischemia
Differential Diagnosis:
o NSTEMI
o Posterior MI ST depression Upright T waves Dominant R waves V1-V3
o o Digoxin toxicity U or sagging type of down sloping ST depression
When does T inversion happen and what cause it ?
o ≥ 1 mm depression, below the isoelectric line or point
o T wave inversion in _aVL only,_ suspicion of impending inferior MI
Differential Diagnosis:
o LVH Strain
o Increased ICP (cerebral T waves)
o Pulmonary embolism
o Ischemia
When Biphasic T-Wave happen
CRITERIA
o Upward wave immediately succeeded with downward wave
o Alarming in V2-V3: Fulfills Wellens A criteria Proximal LAD occlusion Differential
Diagnosis:
o Hyperkalemia
Flat T-Wave
CRITERIA
o Differentiate from ST segment depression which is ≥ 0.5-1 mm in any 2 contiguous leads below the isoelectric line
o Should be between -1 mm of depression up to 1 mm of elevation
Differential Diagnosis:
o Ischemia
o Hypokalemia
Peaked T-Waves
CRITERIA:
o Tall, narrow based, relatively symmetrically peaked o >10 mm height
Differential Diagnosis:
o Hyperkalemia (first thing to think of)
o Hypermagnesemia
o Ischemia
o De Winters T wave
V1-V3 & Upsloping ST depression → proximal LAD occlusion
Wide QRS
CRITERIA:
o >0.12 seconds or 3 small boxes
o Indeterminate point: 0.10-0.12 seconds
Differential Diagnosis:
o Bundle branch block
o Hyperkalemia
o Ventricular tachycardia
o Antidromic WPW Syndrome
o Paced rhythm (with pacemaker)
o Drugs: TCA overdose
When is it LBBB with wide QRS or RBBB with wide QRS ?
Left BBB CRITERIA:
V1-V2: Deep S wave, may sometimes form a bifid pattern
V5-V6: positive deflection with a little dip on the QRS, looks like letter “M”
Right BBB CRITERIA:
V1-V2: characteristics R-S-R’ (r prime) pattern
V5-V6: slurring of S wave
Pathological Q wave
wide Q wave
o Never seen in V1-V3
o >0.04 seconds or 1 small box
o >2 mm deep from isoelectric line or point
Differential Diagnosis:
o Old or New Myocardial infarction
o Pulmonary embolism
o LBBB
o LVH
Low Voltage QRS
Something is blocking the impulse going to the electrodes
Differential Diagnosis: o Pericardial effusion (highest concern)
Poor R-Wave Progression
Normal: R wave exponentially increases from V1-V6
Pathologic:
o R wave doesn’t progressively increase from V1-V6
o S wave is still a bit big in V5-V6
Differential Diagnosis:
o Anterior MI o RVH with Strain
Dominant R-Wave Progressio
Normal: Smaller R waves and bigger S waves in V1-V3 (i) Pathologic: o R wave > S waves in V1-V3 which means greater impulse towards the right o ST depression o Upright T waves (ii) Differential Diagnosis: o Posterior MI (first to think about)
LVH and RVH
Prolonged QT Interval
CRITERIA:
o Recall: Measured from point before Q wave until after T- wave o Female: Long >460 ms o Male: >450 ms
o Requires QT-C for accurate measuring
Use Bazett’s formula to see if truly prolonged o QT-interval should be aboult half of preceding R-R interval o Prolonged QT ↑ risk of Torsades de pointes which can present as polymorphic ventricular tachycardia
Short QT Interval
CRITERIA:
o Short <350 ms
Differential Diagnosis:
o Hyperkalemia
o Hypermagnesemia o Digoxin toxicity
Right Atrial Enlargement (RAE)
CRITERIA
o Lead II, III and aVF: >2.5 mm P-wave:
o Lead V1: Biphasic P-wave → (+) deflection → (-) deflection
Diagnosis: 2D ECHO
o to see for atrial enlargement (iii) Differential Diagnosis: Tricuspid valve stenosis o Pulmonary Hypertension o Pulmonic Valve Stenosis
Right Atrial Enlargement (RAE)
CRITERIA
o Lead II, III and aVF: >2.5 mm P-wave:
o Lead V1: Biphasic P-wave → (+) deflection → (-) deflection
Diagnosis: 2D ECHO
o to see for atrial enlargement
(iii) Differential Diagnosis:
Tricuspid valve stenosis o Pulmonary Hypertension o Pulmonic Valve Stenosis
Left Atrial Enlargement (LAE)
CRITERIA:
o Lead II: bifid camel’s hump / P-wave > 0.04 second (1 small box) o Lead V1: Use to enhance diagnostic ability Biphasic P-wave (-) deflection > (+) deflection Explanation: Since impulse is pulled towards the LA, it moves away from the positive electrode at V1 (right inferior) so (-) deflection > (+) deflection
Differential Diagnosis: o Mitral valve stenosis o Aortic valve stenosis o Systemic HTN causes things to back up into the pulmonary circulation ↑ blood volume and pressure in the left atrium (LA
Short PR-Interval
CRITERIA:
o <0.12 seconds (<3 small boxes)
(ii) Differential Diagnosis:
o WPW Syndrome
o Premature atrial contractions (PAC) in ectopic area somewhere that fires quicker + closer to the AV node = shortening of PR-interval
Prolonged PR-Interval
) CRITERIA:
o >0.20s (>1 big box or >5 small boxes)
(ii) Differential Diagnosis:
o 1st Degree Heart block: same prolonged PR interval throughout the rhythm strip
o 2nd Degree Mobitz Type 1: prolongation progressively gets longer and longer throughout the rhythm strip
o 3rd Degree Heart block: variable prolongation throughout the rhythm strip
Left Axis Deviation (LAD)
(i) Lead reading for R wave:
o Lead I → R wave positive deflection → Left thumb UP
o Lead aVF → S wave negative deflection → CHECK Lead II
o Lead II → negative deflection → LAD
bigger impulse directed to the left side of the heart (ventricle) → ventricular depolarization moves primarily in the left axis → bigger S wave negative deflection
(ii) Causes:
o Obesity Due to elevation of the diaphragmatic level
o LBBB: electrical activity has to come from the right side to the left side
o LVH: thicker more electrical activity pushed to this side
o Inferior Myocardial infarction
o Hyperkalemia
Right Axis Deviation (RAD)
(i) Lead reading:
o Lead II → S wave negative deflection → Left thumbs DOWN
o Lead aVF → R wave positive deflection → Right thumb UP → RAD
Since ventricular depolarization is more deviated to the right and approaches the location of the (+) electrode → bigger positive deflection
(ii) Causes:
o Extremely thin people
o RBBB
Causes the left side of the heart to bring electrical activity to the right side
o RVH
Thick Right ventricle ↑ electrical activity o Anterior MI
o Ventricular tachycardia
↑ electrical activity originating from the left side of the heart which gets pushed to the right side of the heart
Extreme Right Axis Deviation (ERAD)
(i) Lead reading:
o Lead II → S wave negative deflection Left thumbs DOWN o aVF → S wave negative deflection Left thumbs DOWN
(ii) Causes:
o Extreme RVH: RV pulls ↑ electrical activity to it o Ventricular tachycardia:
Electrical focus developing within the left side → ↑ electrical activity towards the right side
o Extremely thin individuals
EKG’S
ECG’s
