Heart block
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Classification
- First-degree heart block - PR interval > 0.2s; no dropped QRS complex
- Second-degree heart block
- Type 1 (aka Mobitz I, Wenkebach) - PR interval increases with each beat until exentually you get a dropped QRS complex
- Type 2 (aka Mobitz II) - intermittent failure of P waves to conduct, not preceded by P wave elongation
- 2:1/3:1 type - regularly dropped QRS complexes with a 2:1 or 3:1 ratio (P:QRS), not preceded by elongated PR interval
- Third-degree heart block (aka complete heart block) - P waves never conduct and thus unrelated on ECG but P to P interval is regular as is R to R interval. (HR = 40bpm usually). Causes: usually CAD, particularly inferior or anterior wall MI.
Management
- First degree - no treatment
- Second-degree - pacemaker where consciousness is affected.
- Third-degree - pacemaker
You can use atropine on the first two, and even on third degree while waiting to put in the pacer.
Drugs to avoid
If a patient has heart block, they need to avoid:
- Anti-arrhythmics - amiodarone, flecainide.
- Beta blockers - such as atenolol, bisoprolol, propanolol.
- Calcium channel blockers - such as verapamil, diltiazem.