Abnormal Heart Rhythms, ECG & Risk Factors of CVD

Question 1

Normal

Rhythm

Answer 1

P wave > Atrial Depolarisation
QRS complex > Ventricular Depolarisation
T wave > Ventricular Repolarisation
U wave > Recovery of Perkinje fibres
PR interval > Tracks atrial impulse through AV node, down
Bundle of His and left & right bundle branches
ST segment
QT interval

Question 2

12- lead ECG

Answer 2

Records 12 different views of the heart and provides a complete ‘picture’ of the electrical activity

1. Positive
2. Negative
3. Equiphasic

Question 3

Reading an ECG Rhythm Strip

Answer 3

1. Determine RHYTHM
   • Paper & Pencil Method
   > Measure the distance between the R-R or P-P intervals of two consecutive waveforms = Regular of Irregular
2. Determine RATE
   • 10 Times Method > If rhythm is IRREGULAR
   > Number of P waves in 6s strip X 10 = Rate (b·min-1)
   • 1500 Method > If rhythm if REGULAR
   > Atrial – No of small squares b/w P waves
   > 1500/[No]=Rate (b·∙min-­‐1)
   > Ventricular – No of small squares b/w R waves
   • Sequence Method
   > Requires table!

Question 4

Conduction of the Heart

Answer 4

Tachycardia = >100 b·min-1
Bradycardia = < 60 b·min-1

SA Node = Pacemaker
Site that generates an ectopic beat is known as:
Ectopic Focus

Question 5

Angina & Arrhythmia

Answer 5

A patient with either form of angina
(stable cf. unstable) typically demonstrates ischaemic changes.
> a dip in the T wave

Arrhythmia:
> An abnormal heart rhythm

Question 6

Myocardial Infarction

Answer 6

Characteristics of Infarction
> ST segment elevation over area of
damage
> ST depression in leads opposite
infarction
> Pathological Q waves
> Reduced R waves
> Inverted T waves

Question 7

Long Q-­‐T Syndrome

Answer 7

A long delay between depolarisation and
repolarisation of the ventricles
Associated with heart disease, syncope and
sudden death due to ventricular arrhythmias
(fibrillation)

Question 8

Atrial Fibrillation

Answer 8

Atrial activity poorly defined

Multiple ectopic foci

Question 9

Atrial Flutter

Answer 9

Arises in the right atrium
Electricity circulates around chamber at
rapid rate (100-150 b·min-1)

Question 10

Ventricular Fibrillation

Answer 10

Immediate CPR & defibrillation required

Question 11

Ventricular Flutter

Answer 11

Immediate CPR & defibrillation required

Question 12

Premature Ventricular Contractions

Answer 12

PVCs may be uni-focal or multi-focal

Question 13

First Degree Block

Answer 13

Prolonged PR interval (>0.20 s); delay at AV node

Question 14

Second Degree Block

Answer 14

Progressive lengthening of PR interval until QRS complex ‘drops’
Generally transient

Question 15

Third Degree Block

Answer 15

Regular P waves and QRS complex, but
working independent from one another
Associated with reduced Q
Pacemaker may be required