ECG And Rhythm Disorders

Question 1

Relevance of ECG

Answer 1

Detects conduction abnormalities,structural abnormalities and perfusion abnormalities

Relatively cheap and easy to undertake,reproducible between people and centers,quick turnaround on results

Question 2

Vector

Answer 2

Has both magnitude and direction
The greater rhe deflection the more muscle

Question 3

P,QRS,T waves

Answer 3

P wave is electrical signal that stimulates contraction of atria
QRS is electrical signal that stimulates contractions of ventricles
T wave signifies relaxation of ventricle

Question 4

Cardiac vectors

Answer 4

SAN:
autorhytmic myocytes,atrial depolarization (p wave)

AVN:
Isoelectric ecg, slow signal transduction and protective

Bundle of his:
Rapid conduction,insulated

Bundle branches:
Septal depolarization AVN (Q)

Purkinje fibres 1
Ventricular depolarization (R)

Purkinje 2
Late ventricular depolarization (s)

Fully depolarized ventricles show isoelectric ECG

Repolarisation seen as T wave

Question 5

Where do the leads measure activity from

Answer 5

Lead I from right arm to left arm
Lead II from right arm to left leg
Lead III from left arm to left leg

Question 6

Placement of leads on chest

Answer 6

V1-right eternal border in 4 ICS
V2-left eternal border in 4 ICS
V4-mid claviculad line in 5th ICS
V3-halfway between V2 and V4
V5-Anterior axillary line at level of V4
V6-mid axillary line at level of V4

Question 7

Polarity of leads

Answer 7

lead I,II,III are bipolar
Rears are unipolar

Question 8

Plane of chest vs limb leads

Answer 8

Chest leads are horizontal limb leads coronal

Question 9

Cardiac axis

Answer 9

Work out positive and negative deflections for both leads,draw triangle and find angle using tan

Question 10

ECG reporting procedure

Answer 10

Recording correct
Review signal and quality of leads
Edify voltage and paper speed
Review patient background

Question 11

Sinus rhythm

Answer 11

Normal
Each p wave followed by QRS
rate regular and normal

Question 12

Sinus bradycardia

Answer 12

Each p wave followed by QRS
Rate regular and slow
Can be healthy caused by medication or vagal stimulation

Question 13

Sinus tachycardia

Answer 13

Each p wave followed by QRS
Rate regular and fast
Often physiological response eg running

Question 14

Sinus arrhythmia

Answer 14

Each p wave followed by QRS
rate is irregular and normalish rate
R-R varies with breathing cycle
When breathing out PNS activated causing decreased HR
When breathing in SNS activated causing increased HR

Question 15

Atrial fibrillation

Answer 15

No distinct p wave
Ossicikatinf baseline as atria contract asynchronously
Turbulent flow pattern increases clot risk
Atria not essential for cardiac cycle due to effect of gravity that can allow ventricles to fill naturally

Question 16

Atrial flutter

Answer 16

Regular saw tooth pattern in baseline (II,III,aVF)
Atria to ventricular beats at a 2:1 ratio or higher
Saw tooth not always visible in all leads

Question 17

First degree heart block

Answer 17

Persistent prolongation of PR interval caused by slow AVN conduction
Regular rhythm
Most benign heart block and progressive disease of ageing

Question 18

Second degree heart block (Mobitz I)

Answer 18

Progressive prolongation of PR interval until best skipped (gets longer and longer and gone)
Most p waves followed by QRS
regularly irregular caused by diseased AVN
Aka wenckebach

Question 19

Second degree mobits II

Answer 19

p waves are regular but only some followed by QRS
No P-R prolongation
Regularly irregular (successes to failures or random)
Can rapidly deteriorate into third degree

Question 20

Third degree (complete)

Answer 20

P waves and QRS are regular but no relationships
P waves can be hidden
Non sinus rhythm

Question 21

Ventricular tachycardia

Answer 21

P waves hidden-dissociated atrial rhythm
Rate regular and fast
At high risk of deteriorating into fibrillation
Shockable rhythm

Question 22

Ventricular fibrillation

Answer 22

Heart rate irregular and 250bpm and above
Heart unable to generate output
Shockable rhythm

Question 23

ST elevation

Answer 23

P waves visible and followed by QRS
Rhythm regular and rate normal
ST segment elevated above isoelectric line
caused by infarction -tissue death by hypoperfusion

Question 24

ST depression

Answer 24

P waves visible and followed by QRS
Rhythm regular and rate normal
ST depressed below isoelectric line
Caused by myocardial ischemia,hypokalaemia or reciprocal changes