4 - ECG at the Bedside 1

Question 1

1 mm / small box = how much time on an ECG?

Answer 1

40 ms

Question 2

5 mm / large box = how much time on an ECG?

Answer 2

200 ms

Question 3

normal PR interval

Answer 3

3-5 small boxes (120-200 ms)

Question 4

normal QRS interval

Answer 4

2-3 small boxes (80-120 ms)

Question 5

normal QTc interval

Answer 5

9-11 small boxes (360-440 ms)

Question 6

normal sinus rhythm rate

Answer 6

60-100 bpm

Question 7

atrial fibrillation on ECG

Answer 7

absent p waves and irregular rate

Question 8

HR assessment from ECG

Answer 8

divide 300 by RR interval expressed as number of large boxes

Question 9

what two leads normally have negative p waves?

Answer 9

aVR and V1

Question 10

ECG sign of LA enlargement

Answer 10

bifid p wave “p-mitrale” due to delayed LA depolarization

Question 11

ECG sign of RA enlargement

Answer 11

tall P wave > 2.5 mm

Question 12

which leads are best for assessing p wave morphology?

Answer 12

2, 3, aVF

Question 13

ECG sign of AV block

Answer 13

PR interval > 200 ms (5 small boxes)

Question 14

causes of PR prolongation

Answer 14

drugs: beta blockers, Ca channel blockers, digoxin, amiodarone, clonidine
acute ischemia / infarction
degenerative or calcific dz of conduction system (irreversible) - Lev’s or Lenegre’s dz

Question 15

tx for irreversible AV block

Answer 15

pacemaker

Question 16

Wolf Parkinson White syndrome ECG findings

Answer 16

short PR interval (120 ms

Question 17

Wolf Parkinson White syndrome mechanism

Answer 17

accessory branch back to AV node causing tachycardia and irregular rhythm

Question 18

ECG signs of bundle branch block

Answer 18

RSR’ pattern in qrs complex in precordial leads

wide qrs complex (>120 ms)

Question 19

how do you distinguish between left and right bundle branch block on ECG?

Answer 19

if signs are in V1/2 > right

if signs are in V5/6 > left

Question 20

what causes bundle branch block (2)?

Answer 20

ischemia/infarction of bundle branch

eccentric hypertrophy of ventricles

Question 21

how do you calculate QTc?

Answer 21

QT / sqrt (RR interval)

Question 22

acquired causes of prolonged QT interval

Answer 22

drugs: anti-arrhythmics, anti-psychotic phenothiazines, TCAs, antifungals
electrolyte abnormalities - low K, Mg, Ca

Question 23

complication of long QT syndrome

Answer 23

Torsades de pointes - varying ventricular tachycardia. Can cause sudden death