Heart block

Question 1

Define:

Answer 1

1st degree - this is when there is prolonged conduction through the AVN

2nd degree - mobitz type 1 (progressive prolongation of conduction through the AVN followed by a missed beat). Mobitz type 2 (intermittent regular failure of conduction)

3rd degree - complete heart block(no association between the atria and ventricle conduction)

Question 2

Aetiology/risk factors:

Answer 2

MI or IHD (most common)

cardiomyopathy or myocarditis

Infective cause (Rheumatic fever or infective endocarditis)

Drugs (digoxin)

Metabolic (hyperkalemia)

sarcoidosis

degeneration of conduction system

Question 3

epidemiology:

Answer 3

most of the pacemakers fitted are for heart block - 250,000 in total

Question 4

symptoms:

Answer 4

1st degree and MT1 are usually asymp

MT2 and 3rd degree - Strokes-Adams attack (due to ventricular asystole)
–> dizziness, SOB, chest pain, syncope, palpitations, HF symptoms

Question 5

signs:

Answer 5

usually no signs

In MT2 and 3rd degree - JVP shows cannon a waves + signs of HF (hypotension etc)

Question 6

investigations:

Answer 6

ECG are the gold standard:

• 1st degree - PR interval greater that 0.2 seconds
• MT1 - increasing PR interval followed by dropped beat (no p wave)
• MT2 - fixed prolonged PR interval with random dropped beat (no p wave)
• 3rd degree - no association between P waves and qrs complexes (these are usually narrow as they come from the bundle of HIS)

CXR - cardiomegaly, pulmonary oedema

Bloods - troponin, cardiac enzymes, TFT, digoxin + U+ Es.

Echo - vegetations and wall abnormalities

Question 7

management:

Answer 7

permanent pacemaker in 3rd degree and MT2 –> in MT1 if asymptomatic

Acute - use IV atropine and temporary external pacemaker

Question 8

complications:

Answer 8

asystole

cardiac arrest

Heart failure

complications of inserting a pacemaker

Question 9

Prognosis:

Answer 9

those with MT2 and 3rd degree there is an indication of an underlying serious cardiac condition.