Heart Block

Question 1

What is first degree heart block?

Answer 1

PR interval prolonged + unchanging

No missed beats

Question 2

What is second degree heart block?

Answer 2

Mobitz Type I (Wenckebach): progressive prolongation of PR interval until a QRS is missed, then pattern resets
Mobitz Type II: QRS’s regularly missed. Pattern is number of normal conductions per failed ones (e.g. 2:1 or 3:1)

Question 3

List 8 pathological causes heart block

Answer 3

MI/ IHD
Infection (e.g. rheumatic fever, infective endocarditis)
Inflammation (Myocarditis)
Drugs (e.g. digoxin, B-blockers)
Metabolic (e.g. hyperkalaemia)
Infiltration of conducting system (e.g. sarcoidosis, tumour)
Degeneration of conducting system
Structural abnormalities

Question 4

What is third degree heart block?

Answer 4

Complete heart block

No impulses passed from atria to ventricles so P waves + QRS appear independently

Question 5

What symptoms are usually experienced in patients with first or second degree heart block?

Answer 5

Asymptomatic

Question 6

List 5 risk factors for heart block

Answer 6

Age
Increased vagal tone
Use of AVN blocking agents
Underlying CVD
Cardiac surgery/ trauma

Question 7

What symptoms may be experienced in Mobitz Type II + 3rd Degree heart block?

Answer 7

Stokes-Adams Attacks (syncope caused by ventricular asystole)
Dizziness
Palpitations
Chest pain

Question 8

Describe the signs of heart block on examination

Answer 8

OftenNORMAL

Check for signs of potentialcause of heart block

Question 9

What signs may be seen in complete heart block?

Answer 9

Slow, large volume pulse

CANNON A WAVES in JVP (when atria + ventricles contract simultaneously)

Question 10

What signs may be present in Mobitz Type IIand3rd Degree Heart Block?

Answer 10

Signs of reduced cardiac output (e.g. hypotension, HF)

Question 11

What is the gold standard investigation for heart block?

Answer 11

ECG

Question 12

What bloods should be measured in heart block that can indicate the cause?

Answer 12

Troponin (raised)
K+ (extremes)
Ca2+ (extremes)
pH (alkalosis/ acidosis)
Digitalis (Normal/ elevated)

Question 13

Describe the ECG in first degree heart block

Answer 13

Fixed prolonged PR interval (> 0.2 s)

Question 14

Describe the ECG in second degree heart block

Answer 14

Mobitz Type I: progressively prolonged PR interval, culminating in a P waveNOTfollowed by a QRS complex. Pattern resets

Mobitz Type II: intermittently a P wave isNOTfollowed by a QRS. Regular patternof P waves not followed by QRS (e.g. 2:1 or 3:1)

Question 15

Describe the ECG in third degree heart block

Answer 15

Complete Heart Block: no relationship between P waves + QRS complexes. If QRS is initiated in the:
Bundle of His: narrow complex
More distally: wide complex + slow rate (~ 30 bpm)

Question 16

What 4 features may be seen on CXR in heart block?

Answer 16

Cardiomegaly
Hilar lymphadenopathy
Coronary/ valvular calcification
Pulmonary oedema

Question 17

What 4 features may be seen on echocardiogram in heart block?

Answer 17

Ventricular dysfunction/ hypertrophy
Valvular disease
Wall-motion abnormalities
Vegetations

Question 18

What is the management plan in symptomatic first degree and second degree (T1) heart block?

Answer 18

Stop all AV-nodal blocking medications

If severe consider permanent pacemaker implantation

Question 19

What is the management plan in asymptomatic first degree heart block?

Answer 19

Low risk of progression

Re-check ECG on a regular basis

Question 20

List 4 complications of heart block

Answer 20

Asystole
Cardiac arrest
Heart failure
Complications of pacemaker inserted

Question 21

What is the management plan in second (T2) and third degree heart block?

Answer 21

Stop all AV-nodal blocking medications
Treat reversible causes: ACS, medication toxicity, metabolic disturbances
If no reversible causes; implant permanent pacemaker

Question 22

Describe epidemiology of heart block

Answer 22

1st + 2nd degree: Uncommon/ rare

Acquired 3rd degree: Common

Question 23

Describe the prognosis in heart block

Answer 23

Good with tx