Heart Blocks (1*) Flashcards
1st Degree Heart Block:
What occurs here?
What’s it caused by?
What is seen on ECG?
How is it managed?
➊ Prolonged conduction of electrical activity through the AV node
➋ • High vagal tone (e.g. athletes)
• Inferior MI
• Electrolyte abnormalities (e.g. hyperkalaemia)
• Drugs - non-DHP CCBs, b-blockers, digoxin
➌ Prolonged PR interval (>200ms/5 small squares)
➍ Is benign, therefore doesn’t require any management. Any underlying cause should be treated.
2nd Degree Heart Block:
What occurs here?
What ECG change is seen with Mobitz I (Wenckebach’s phenomenon)?
→ How is it managed?
What ECG change is seen with Mobitz II?
→ How is it managed?
➊ Some atrial impulses don’t make it through the AV node to the ventricles, therefore there are instances where p waves don’t lead to QRS complexes
➋ Progressive lengthening of PR interval, which results in a p wave that fails to conduct a QRS
→ Generally asymptomatic and doesn’t require any management as the risk of complete heart block/asystole is low
➌ Set ratio of P waves to QRS complexes e.g. 2:1 or 3:1 - Constant PR interval
→ Pacemaker due to the risk of Complete heart block and Asystole
N.B. Pts must notify DVLA and stop driving for at least 1 week after a pacemaker is inserted.
3rd Degree/Complete Heart Block:
What occurs here?
What does the ECG show?
What is there a huge risk of here?
How is it managed?
➊ Atrial impulses fail to be conducted to the ventricles
➋ Severe bradycardia and dissociation between the p waves and QRS complexes
➌ Asystole
➍ Pacemaker
N.B. Pts must notify DVLA and stop driving for at least 1 week after a pacemaker is inserted.
N.B. Pacemakers are categorised into external and internal. The external type (i.e. external pacing, like that used in Mobitz II or CHB) is almost always used for temporary stabilisation of the patient before definitive management with an implantable (internal) pacemaker can be done.
What should be done if the pt has adverse effects (e.g. HF, MI, syncope, shock)?
Give IV Atropine!
