Identifying Arrhythmias & Heart Blocks

Question 1

1st Degree AV Block

Answer 1

Prolonged PR interval >5 small boxes

Question 2

2nd Degree Type I Mobitz AV Block (Wenckebach)

Answer 2

Blocked P-waves
Progressive prolongation of PR intervals
Dropped QRS
Cycle repeats itself and PR interval resets
Fixed ratio of P-waves to QRS complexes per cycle like x4 P-waves for every x3 QRS = 4:3 block

Question 3

2nd Degree Type II Mobitz AV Block

Answer 3

Intermittent non-conducted P-waves
Constant PR intervals
Broad QRS
Fixed number of P-waves per QRS like 3 for every 1 = 3:1 block
Can progress to 3rd degree

Question 4

3rd Degree AV Block

Answer 4

No relationship between P-waves and QRS - varied PR intervals
Can progress to cardiac arrest
Independent, regular rhythms

Question 5

RBBB

Answer 5

“Marrow”
V1 = rsR pattern in QRS
V6 = broad, low hanging S-wave

Question 6

LBBB

Answer 6

“William”
V1 = srS pattern in QRS
V6 = broad, notched, double R wave

Question 7

LAFB

Answer 7

LAD
Inferior leads = negative
Lateral limb leads = positive

Question 8

LPFB

Answer 8

RAD
Inferior leads = positive
Lateral limb leads = negative

Question 9

Bifascicular Block

Answer 9

Either:
RBBB + LAFB or RBBB + LPFB

Question 10

Trifascicular Block

Answer 10

“Complete heart block”
Either:
Bifascicular Block + 1st degree AV Block, or
Bifascicular Block + 2nd degree AV Block, or
Bifascicular Block + 3rd degree AV Block, or
RBBB + LAFB + LPFB, or
RBBB + LBBB

Question 11

Orthodromic AVRT

Answer 11

Normal QRS
Inverted P-waves after QRS
Regular tachy rhythm 150-250bpm

Question 12

Antidromic AVRT

Answer 12

Wide QRS with Delta wave
Inverted P-waves after QRS

Question 13

WPW Syndrome

Answer 13

Short PR interval <120ms
Broad QRS with Delta wave

Question 14

AVNRT

Answer 14

Absent or hidden P-waves in QRS
If present P-waves = inverted after QRS
Narrow QRS
Regular tachy rhythm 150-250bpm
Short RP intervals

Question 15

Junctional Rhythms

Answer 15

Normal = 40-60bpm
Accelerated = 60-100bpm
Tachy = >100bpm
P-waves absent/hidden/inverted/occurring after QRS
Narrow or normal QRS
Short PR interval

Question 16

Ectopic Atrial Beat (PAC)

Answer 16

Abnormal P-wave morphology
P-waves may be notched in T-waves or inverted or notched or flattened
Normal QRS
Varied PR interval depends on location of ectopic focus
Can be couplet/triplet/bigeminy/trigeminy

Question 17

A-Fib

Answer 17

Irregularly irregular rhythm
Absent P-waves
Fibrillatory waves
Can have associated rapid or slow ventricular response

Question 18

Atrial Flutter

Answer 18

Organised, regular rhythm
Sawtooth pattern
Normal QRS
Repeated P-waves in a ratio against QRS eg 2:1 / 3:1
Atrial rate typically double ventricular rate

Question 19

VT

Answer 19

> 100bpm
Broad QRS
P-waves absent or dissociated from QRS
Extreme axis deviation
Abnormal T-waves
Sustained = >30 seconds
Non-sustained = <30 seconds
Monomorphic = regular rhythm, one focus
Polymorphic = irregular rhythm, multiple foci (Torsades)

Question 20

Hyperkalaemia

Answer 20

Peaked T-waves
ST-elevation
Prolonged PR interval
Broad QRS

Question 21

Hypokalaemia

Answer 21

Inverted T-waves
ST-depression
U-waves

Question 22

Long QT Syndrome (LQTS)

Answer 22

Prolonged QT interval
>440ms in men, >460ms in women
Abnormal T-waves
Associated Torsades de Pointes

Question 23

Torsades de Pointes

Answer 23

Looks like VT
Twisted QRS

Question 24

Ectopic Ventricular Beats (PVCs)

Answer 24

Irregularly irregular rhythm
Broad QRS
Extra QRS
Disappear after a certain HR (stress test can identify)
Couplet/triplet/bigeminy/trigeminy

Question 25

V-Fib

Answer 25

Chaotic, disorganised rhythm
Fibrillation waves