ECG By Cameron McCloskey

Question 1

How many large squares pass through per minue on an ECG?

Answer 1

300

Question 2

What is a normal PR length?

Answer 2

0.12-0.2 seconds

Question 3

What is a normal QRS length?

Answer 3

0.08-0.12 seconds

Question 4

What is a normal QT interal length?

Answer 4

0.35-0.43 seconds

Question 5

What may cause a prolonged QT interal?

Answer 5

Drugs

Electrolyte abnormalities (hypokalaemia, hypocalcaemia etc.)

Question 6

What can cause deviation in the QRS complex?

Answer 6

Venticular hypertrophy (either left or right)

Question 7

Deviation in the QRS complex is best seen in which leads?

Answer 7

I, II and III

Question 8

Which distinctive patterns will be present on the ECG for right axis deviation?

Answer 8

• Increases in lead III QRS
• Negative deflection in lead I QRS

The right ventricle now has more influence on the QRS than the left

Question 9

Which conditions are likely to cause right axis deviation and why? copd

Answer 9

Pulmonary conditions

e.g. PE

These put strain on the right side of the heart so lead to hypertrophy

Question 10

How does left axis deviation present on an ECG?

Answer 10

Negative QRS complex in lead III

Negative QRS complex in lead II

Question 11

What causes left axis deviation? 2

Answer 11

LVH or a conduction defect

Question 12

Which area of the heart do leads V1 and V2 “look” at and which pattern do they nrmally observe?

Answer 12

Right ventricle

• Small upward deflection (R wave - septum depolarised)
• Large downward deflection (Q wave - main muscle mass depolarised)

Question 13

Which area of the heart do leads V5 and V6 “look” at and which pattern do they nrmally observe?

Answer 13

Left ventricle

• Small initial downward deflection (septal Q wave)
• Large upward deflection (R wave - main muscle mass depolarised)

Question 14

How is it possible to tell on an ECG where the interventricular septum is present?

Answer 14

When R and S waves are roughly equal

That happens around V3/4

Question 15

How is an ECG reported on? (6)

Answer 15

1. Verify patient details
2. Check date and time of ECG
3. Check paper calibration
4. Determine axis
5. 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
6. Look at individual leads for volatge criteria changes or ST or T wave changes

Question 16

what is QUADRANT METHOD ? 4

Answer 16

E

Question 17

How to calculate HR on an ECG

Answer 17

Question 18

How to determine the type of acut coronary syndrome

Answer 18

Question 19

How to determine the type of acut coronary syndrome

Answer 19

it happen due to plague rapture in the coronary arteries result in blood vessel blockage

Question 20

1. P wave
2. PR Segmen
3. PR Interva
4. QRS complex
5. ST Segment -the flat line between S and T
6. T wave
7. QT Interval- At the start of the Q wave to the end of T wave

Answer 20

1. Atrial depolarization (From the SA node spreads throughout the atria)
2. 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
3. Time from when SA node fires > AV node depolarization > getting ready to send action potentials down to ventricles
4. Time from when SA node fires > AV node depolarization > getting ready to send action potentials down to ventricles
5. Ventricular depolarization But no net electrical activity in any direction, ventricles are just holding on to it
6. Ventricular repolarization
   
   1. Time period right before the Q wave starts (ventricular depolarization) up until the end of T wave (ventricular repolarization)

Question 21

1. RV
2. Basal septum
3. Anterior wall of the heart
4. High lateral wall of the LV
5. Inferior wall of the hear

Answer 21

1. aVR and V1-V3
2. aVR and V2-V3
3. V2-V4
4. Lead I, avL and V5-V6
5. Lead II, III, avF

Question 22

What are the steps for reading ECG

Answer 22

1. Rhythm o R-R interval constant? It’s regular. o R-R interval NOT constant? It’s irregular
2. 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
3. (iv) QRS o <0.12 seconds or 3 small boxes = Narrow o >0.12 seconds or 3 small boxes = Wide
4. 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?
5. P-R Interval (block) o Time:  <0.2 seconds = Normal  >0.2 seconds = Prolonged  Constant  Variable  Progressively Longer

Question 23

1. Narrow + Regular S
2. Narrow + Irregular
3. Wide + Regular
4. Wide + Irregular

Answer 23

1. 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.
2. Atrial fibrillation (most common) Variable A-flutter Multifocal atrial tachycardia
3. Ventricular tachycardia, until proven otherwise Supraventricular tachycardia with Bundle branch block Sinus tachycardia with Bundle branch block Antidromic WPW
4. Polymorphic Supraventricular tachycardia Atrial fibrillation with WPW Atrial fibrillation with Bundle branch block

Question 24

When is it called ST elevation

Answer 24

• 1 mm in any 2 contiguous leads except V2-V3  true ST segment elevation • 2 mm in V2-V3  true ST segment elevation

Question 25

When is it ST depression and what cause it ?

Answer 25

 ≥ 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

Question 26

When does T inversion happen and what cause it ?

Answer 26

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

Question 27

When Biphasic T-Wave happen

Answer 27

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

Question 28

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

Question 29

Peaked T-Waves

Answer 29

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

Question 30

Wide QRS

Answer 30

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

Question 31

When is it LBBB with wide QRS or RBBB with wide QRS ?

Answer 31

**_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

Question 32

Pathological Q wave

Answer 32

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

Question 33

Low Voltage QRS

Answer 33

Something is blocking the impulse going to the electrodes Differential Diagnosis: o Pericardial effusion (highest concern)

Question 34

Poor R-Wave Progression

Answer 34

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

Question 35

Dominant R-Wave Progressio

Answer 35

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)

Question 36

LVH and RVH

Answer 36

Question 37

Prolonged QT Interval

Answer 37

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

Question 38

Short QT Interval

Answer 38

CRITERIA: o Short \<350 ms Differential Diagnosis: o Hyperkalemia o Hypermagnesemia o Digoxin toxicity

Question 39

Right Atrial Enlargement (RAE)

Answer 39

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

Question 40

Right Atrial Enlargement (RAE)

Answer 40

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

Question 41

Left Atrial Enlargement (LAE)

Answer 41

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

Question 42

Short PR-Interval

Answer 42

**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**

Question 43

Prolonged PR-Interval

Answer 43

) 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

Question 44

Left Axis Deviation (LAD)

Answer 44

(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

Question 45

Right Axis Deviation (RAD)

Answer 45

(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

Question 46

Extreme Right Axis Deviation (ERAD)

Answer 46

(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

Question 47

EKG’S ECG's

Answer 47