ECG

Question 1

Recall the nomenclature terms of ECG (electrodes, cables/wires and leads)

Answer 1

Electrodes are the part stuck onto the skin-or clamps
cables are what connect electrodes to the machine
leads are the vision direction of the ECG connecting between two electiodes (exemple-rule of L describes Lead I, II and III (RA LA, RA LL, LL LA)

Question 2

What is a cardiac vector?

Answer 2

A vector is a quantity that has maginitude and direction
For the heart, represented for an arrow with a NET direction and size= magnitude
The observation is done with anode (-) being a “dip”-so if vector towards arrow, dip down, and cathode-dip up
eg: lead II RA LL-if vector going perfectly (parrallel) towards right arm-then large up dip on ECG)
If line is not quite parralelle, dips will reduce and withen
If line perpendicular-isoelectioc line-no change in net voltage in that direction

Question 3

Recall the 4 waves visible on and ECG and what they relate to

Answer 3

P wave-1st wave-stimulation of atria and contraction-artial systole)
QRS-set of activation of ventricular contraction -large peak with dip on either side (p relxation is hidden there)
T- relaxation of the ventricules

Question 4

Recall the events of the contraction system of the heart, in relation to ECG waves. Recall cardiac vectors of each event

Answer 4

Starts in sinoatrial node-down artial tracts to left and right atrium (P wave)
Stops for a while at atrioventicular node PQ break (temporalisation)
then fast down bundle of his (insolated so no ECG mark) to apex
Starts with septum (q wave)-gives a base to contract upon-then spread through right and left Pukinje fibers- venticule contracts R wave. Late contraction/depolarisation makes S wave
SAN has a solid right side (lightly towards + of lead II),
septal has a small upwards (towards + of lead II)
Pukinje fibers-strong towards positive (leg) of lead II
Spread and late depolarisation upwards (towards -)
repolarisation has a negative wave, but goed towards - -so makes a +

Question 5

List the different electrodes and their placement on the body

Answer 5

Lead I, II and III go on arms and legs -rule of L to rememebr ( number of L total in each lead is number of lead)
Lead I -Right arm-, Left arm+
II-RA-, LL+
III-LL+ LA-
Then V1 and V2 electrodes go either side of sternum V1-right) on 4 insercostal space
V4 goes on left midclavicular line (nipple line)-5 insercostal
V3 between V2 and V3
V5-anterior axillary line (level of crease of armpit-level with V4)
V6-mid auxillary line (middle of armpit down to V4 level)

Question 6

How do 9 electrodes make 12 leads?

Answer 6

Some leads use hypothetical points-such as the mod point between LA and LL and compare to RA-AvR (same with other Av (R/F)

Question 7

What are the normal ranges for the main ECG intervals?

Answer 7

RR-0.6-1.2s (gives bpm if /60 or 300/#of squares between)
P wave duration-80ms
PR-120-200ms
QRS <120ms
QT <420ms (but always use QTcorrected because heart rythm impact)
T wave (<160ms)
heart rate 60-100BPM
QRS axis -30 - +90°

Question 8

What 3 main abnormalities do ECG detect in the heart?

Answer 8

ECG can be used for conduction abnormalities (100%), for most structural abnormalities and some perfusion abnormalities (ischeamia)

Question 9

Describe the steps to take in a systematic approach to ECG analysis

Answer 9

Start always with-is it correct recording (is it the right person), then review signal quality and leads (too much noise?). Verify voltage and paper speed (25mm/s and 10mV), then review any background from patient that might cause abnormalities)
Step 1: Heart rate and rhythm (regular or not) (RR intervals)
Step 2-P wave (<80ms) and PR interval
Step 3-QRS duration (<120ms)
Step 4: QRS axis (between -30 and +90)
Step 5: ST segment
Step 6: QT interval (<420ms)
Step 7: T wave
Then always double check any findings

Question 10

Recall the main ECG properties of sinus rhythm

Answer 10

Each P wave is followed by QRS wave, heart rate is normal and REGULAR-everything else unremarkable

Question 11

Recall the main ECG properties of sinus bradychardia

Answer 11

Each P wave is followed by QRS wave, heart rate is low (<60bpm large RR intevrals) and REGULAR-everything else unremarkable
Can be healthy, caused by medication or vagal stimulation

Question 12

Recall the main ECG properties of sinus tachychardia

Answer 12

Each P wave is followed by QRS wave, heart rate is fast (>100bpm small RR intevrals) and REGULAR-everything else unremarkable
Can be healthy, often a physiological response to another problem

Question 13

Recall the main ECG properties of sinus arrhythmia

Answer 13

Each P wave is followed by QRS wave. Rate is IRREGULAR, but heart rate is normal-ish
Not always pathological

Question 14

Recall the main ECG properties of Atrial fibrillation

Answer 14

Oscillating baseline-atria contacting asynchonously
Rythm can be irregular and slow
=> increase clot risk, but atria not essential so doesnt kill directly

Question 15

Recall the main properties of Atrial Flutter

Answer 15

Called saw tooth pattern-baseline sawtooth in II, III and aVF
The ratio of tooth to QRS is the same in one patient but not always between patient
Tooth not always visible in all leads

Question 16

Recall the main properties of 1st degree heart block

Answer 16

Junctional problem
Prolonged ST segment/interval because of slow Atrioventricular conduction
Regular rhythm of P:QRS
More or less benign and progessive with age

Question 17

Recall the main ECG properties of 2nd degree heart block (Mobitz I) (Wenckebach)

Answer 17

gradual prolongation of the PR interval-until beat skipped : some p waves dont have a QRS
Regularly irregular -ratio between p:QRS and skipped QRS stays identical in a patient
caused by a diseases AV node

Question 18

Recall the main ECG properties of 2nd degree heart block (mobitz II)

Answer 18

P waves are regular, but only some are followed by QRS
no PR prolongation like mobitz I
Regularly ireegular between successes (QRS present) and failure
Can deteriorate into 3rd degree heart block

Question 19

Recall the main ECG properties of 3rd degree heart block (complete)

Answer 19

P and QRS waves are regular, but they have no relationships with one another (eg: p wave every 300ms, QRS every 500 ms, but no p before QRS)
The ventricules can beat on their own, but slower without AV node
P waves can be hidden by QRS or T’s
Truely non-sinus rhythm as atrial has no control

Question 20

Recall the main ECG properties of Ventricular Tachycardia

Answer 20

Large sawtooth pattern (not exactly but for image) of large QRS. P waves hidden within (small notches) No baseline-completely dissociated with atrial rhythm
Regular and fast-ventricules beat before blood fills and repeat
High risk to deteriorate into fibrillation (cardiac arrest) but shockable by definirilator

Question 21

Recall the main ECG properties of Ventricular Fibrillation

Answer 21

Heart rate very high (>250bpm), and all the waves dont ressemble one another. No baseline, no p, t or any recognisable waves
heart unable to output blood
Shockable but very dangerous-death

Question 22

Recall the main ECG properties of ST elevation

Answer 22

P waves followed by QRS, rhythm regular and normal, but ST segment elevated (2mm is cutoff for definite-but if elevated but less-still damage)
caused by infraction of heart tissue (hypoperfusion)

Question 23

Recall the main ECG properties of ST depression

Answer 23

P waves followed by QRS, rhythm regular and normal, but ST segment depressed under baseline ( 2mm is cutoff for definite-but if depressed but less-still damage
Caused by myocardial ischaemia (coronary insuficciency)