ECG Conduction Problems

Question 1

Second degree block

Answer 1

Mobitz type2 occasional no conducted beats Wenckeback progressive lengthening of the PR interval, then no conducted p wave, followed by repetition of cycle 2:1 or 3:1 block 2 or 3 p waves per QRS

Question 2

Third degree complete block

Answer 2

No relationship between p wave and QRS Usually wide QRS complexes QRS rate less than 50 min Sometimes narrow QRS 50-60min

Question 3

RBBB

Answer 3

QRS 120ms RSR pattern Usually dominant R1 wave in lead V1 Inverted T waves V1 sometimes V2 V3 Deep S wave lead V6

Question 4

Left anterior hemiblock

Answer 4

Left axis div Deep S waves 2 and 3 Slightly wide QRS

Question 5

LBBB

Answer 5

QRS greater than 120ms M pattern V6 sometimes in V4 -V5 No septal Q waves Inverted T waves 1,VL, V5,V6 sometimes V4

Question 6

Common super ventricular rhythms

most commom SVT are caused by reentry phenomenon

Answer 6

Sinus rhythms

Atrial extra systole Junctional (AV nodal )

Atrial tachy

Atrial flutter

Junctional (AV nodal) tachy Junctional (AV nodal)

Atrial fibrillation

Question 7

Rhythm abnormalities

Answer 7

Extra systole single early beats suppressing the next sinus beat Escape beat absence of sinus beat followed by late single beat Tachy Brady

Question 8

Common ventricular rhythms

Answer 8

Ventricular extra systole

Accelerated idioventricular rhythm

Ventricular escape single beats or complete heart block Ventricular fibrillation

Question 9

Myocardial infarction Sequence of ECG change

Answer 9

1 normal ECG

2 raised ST segment

3 Appearance of Q waves

4 normalisation of ST segment

5 inversion of 5 waves

Question 10

Site of infarction Anterior infarction changes classically in leads

Answer 10

V3 V4 but often seen V2 And V5

Question 11

Site of Inferior infarction changes in leads

Answer 11

3 and VF

Question 12

Lateral infarction changes in leads

Answer 12

1, VL, V5 and V6

true posterior infarction dominant R wave in lead V1

Question 13

Pulmonary Embolism Possible patterns

Answer 13

Normal ECG with sinus tachy

Peaked P waves

RAD RBBB

Dominant R waves V1

Inverted T waves in leads V1 V3

Deep S waves in V6

S waves in 1 Q and inverted T waves in 3

Question 14

Right ventricular hypertrophy

Answer 14

RAD

Tall R waves lead 1

T wave inversion in lead V1 V2 sometime V3 and even V4

Deep S wave in V6

Sometimes RBBB

Question 15

Left ventricular hypertrophy

Answer 15

R waves in lead V5 or V6 greater than 25 mm

S waves in lead V1 or V2 greater than 35mm

Inverted T waves in leads 1, VL, V5 V6 sometimes V4

Question 16

Left atrial hypertrophy How would the P waves look

Answer 16

Bifid P waves

Question 17

Right atrial hypertrophy How would the P waves look

Answer 17

Peaked P waves

Question 18

P QRS apparently not 1 to 1 consider what

Answer 18

1 P wave is actually present but not easily seen try

2 V1 2 QRS is irregular the rhythm is probably atrial fib and what seem to be p waves or not

3 if the QRS rate is rapid and no P waves a wide QRS indicates ventricular tachy and narrow QRS indicates junctional (AV nodal) tachy If QRS is rate is slow, it’s probably an escape rhythm

Question 19

P QRS more than 1 to 1 Consider what

Answer 19

If P wave rate >300min is atrial flutter

If P wave rate 150-200 min two P waves per QRS atrial tachy with block

If the P wave rate is normal 60-100min 2 to 1 SR second degree block

PR interval appears to be different with each beat third degree block

Question 20

Wide QRS greater than 120ms

Answer 20

SR

BBB

WPW

Ventricular extra systole

Ventricular tachycardia

Complete heart block

Question 21

Q waves normal left to right depolarisation interventricular septum

Answer 21

Small (septal) Q waves normal seen in leads 1 VL andV5 V6

Q waves in 3 and avr is normal variant

Q waves in more than one lead longer than 40ms and deeper 2mm indicate infarction

Q waves indicate site of infarction

under normal circumstances q waves should been seen in right side leads v1_v3

Question 22

ST segment depression

Answer 22

Digoxin: ST slopes downwards depression Ischaemia: ST flat segment depression

Question 23

T wave inversion

normal t wave amplitude limb / precordial

Answer 23

Normal in leads VR V1 and V2 and V3 in black people Ventricular rhythms BBB Mi Right and left ventricular hypertrophy WPW

less than 5mm limb

Less than 15mm precordial

Question 24

First degree block

Answer 24

One P wave per QRS PR interval greater than 200ms