ECG

Question 1

1st degree heart block

Answer 1

Constant prolonged PR intervals

Question 2

2nd degree heart block, type 1

Answer 2

Gradaully lengthening PR intervals, followed by dropped QRS

Question 3

2nd degree heart block, type 2

Answer 3

Constant prolonged PR interval, with dropped QRS complexes

Question 4

3rd degree heart block

Answer 4

No relationship between PR intervals and QRS complexes

Question 5

Bundle branch block

Answer 5

Normal PR interval

Lengthened QRS duration

Question 6

Right bundle branch block on ECG

Answer 6

Often doesn’t show on ECG
Right ventricle depolarises after left ventricle
Produces second R wave

• MarroW -
  QRS in V1 look like an M
  QRS in V6 look like a W

QRS complexes wide

Question 7

Left bundle branch block on ECG

Answer 7

Second R wave

• William -
  QRS in V1 look like a W
  QRS in V6 look like an M§

Question 8

Causes of LBBB

Answer 8

Iscahemic disease

Aortic stenosis

Question 9

Atrial tachycardia

Answer 9

P waves superimposed on the T wave of the preceding beat

Fast rhythm >150 bpm

Question 10

Atrial flutter

Answer 10

Sawtooth pattern - no flat lies between P waves

rate >250 bpm - heart cannot beat that fast - associated with block

Question 11

Junctional/Nodal tachycardia

Answer 11

P wave very close to QRS - may not be visible
Normal QRS

small re-entry circuits around the AVN

Question 12

What does carotid sinus pressure do and what does it help differentiate between?

Answer 12

By applying pressure to the carotid sinus you can stimulate the AV and SA nodes via vagal stimulation.

This will reduce the frequency of discharge of the SA node, and increase the time of conduction across the AV node.

Reduce the rate of some arrhythmias
Completely stop some arrhythmias

No effect on ventricular tachycardias - differentiate

Applying the pressure basically reduces the frequency of QRS complexes, and allows the underlying atrial arrhythmia to become more visible.

Question 13

Ventricular tachycardia

Answer 13

wide and abnormal QRS complexes
but regular

T waves difficult to identify

No P waves

Question 14

Differentiating between VT and BBB with supraventricular tachycardia

Answer 14

If the patient has just had an MI it is likely to be VT

Look carefully for P waves - present in BBB but not VT

QRS >160ms (4 small squares) most likely to be ventricular

Left axis deviation suggests ventricular

Question 15

Atrial fibrillation

Answer 15

no p waves
irregularly irregular

normal shape QRS
normal T waves

Question 16

ventricular fibrillatin

Answer 16

no pattern

no QRS, no P, no T

Question 17

Wolff-Parkinson-White Syndrome

Answer 17

Accessory pathway
- pathway of Kent
preexcitation of the ventricles, bypass AVN

majority of patients asymptomatic, seen on ECG:
delta wave
short QRS complex
short PR interval
right axis deviation 
sinus rhythm

during re-entry tachycardia:
tachycardia
no p waves

Question 18

ECG with Pacemaker present

Answer 18

Occasional P waves, not related to QRS

QRS is preceded by a big spike – which is the pacemaker stimulus.

QRS complexes are broad – because pacemakers usually stimulate the right ventricle – and thus the depolarisation is ventricular in origin.