ECG

Question 1

Approach to an ECG (6 steps)

Answer 1

1. Calculate the rate
2. Is the QRS wide or narrow
3. Is the RR interval regular or irregular?
4. Is there a P for every QRS
5. Is there a QRS for every P

(are they related)

6. Is the rhythm sustained or paroxsymal?

Question 2

Calculation of instantaneous heart rate on ECG

Answer 2

25mm/s - divide 1500 by the number of small boxes between R’s

50mm/s - divide 3000 by the number of small boxes between R’s

Question 3

Pen x10 rule

Answer 3

Count the number of QRS within 30 big boxes

25mm/s x this by 10

50mm/s x this by 20

Question 4

How to remember einthoven’s triangle

Answer 4

Lead 1 = 1L = left arm to right arm

Lead II = 2L = Right arm to left leg

Lead III = 3L = Left arm to left leg

Question 5

Classes of anti-arrythmics

Answer 5

I = sodium channel blockade (lidocaine, etc.)

II = beta-blockers

III = potassium channel blocker (Sotalol and amiodarone)

IV = calcium channel blocker (Diltiazem)

Digocine

No body kills cats

Question 6

What is the rhythm?

Answer 6

Rarely paroxysmal

Question 7

What is the rhythm?

Answer 7

Question 8

Mobitz type 1 vs type 2 AVB

Answer 8

Mobitz 1 = progressive PR interval before a beat is dropped

This is normally vagally mediated and not pathologic

Mobitz 2 = fixed interval

This is normally pathologic and likely due to AV nodal disease.

Question 9

What is the rhythm?

Answer 9

Question 10

What is the rhythm?

Answer 10

Question 11

What is the rhythm?

Answer 11

Question 12

What is the rhythm?

Answer 12

BBB

Occurs in pulmonic stenosis

Question 13

Deflections of the QRS in RBB vs. LBB?

Answer 13

RBB is negative in lead 2

LBB is positive in lead 2

Question 14

What is the rhythm?

Answer 14

Question 15

What is a wandering pacemaker?

Answer 15

Varying amplitude of P-waves. This occurs in dogs because the pacemaker site within the SAN can vary in its position.

Question 16

Torsade de Pointes

Answer 16

Results from Q-T prolongation

Treatment = magnesium

From what I can gather it just means that the QRS’s are of different sizes.

Question 17

R on T phenomenon

Answer 17

This is where a QRS extrasystole goes over the top of the T wave. This is very bad as it is essentially a depolarisation occuring when the heart should be repolarising.

Question 18

Cardiac potential and ECG changes with hyperkalaemia in order of severity.

Answer 18

Hyperkalaemia decreases the resting membrane potential in mild elevations (5.6-6.5mEq/L) and leads to faster ventricular repolarisation but this is only in the mild stages, at later stages it leads to more severe changes.

1. Tented T-wave as ventricular repolarisation is faster
2. Sinus bradycardia (phase 4 slope is less steep)
3. Widening of the QRS (6.6 - 7.5)
4. Decrease in R-wave aplitude (6.6 - 7.5)
5. P-R prolongation (7.0-8.5)
6. Atrial standstill (7.0-8.5)
7. Death (>8.5)

Question 19

Changes with hypokalaemia

Answer 19

1. Increased resting potential (more negative)
2. Prolongs repolarisation