PR Interval >0.20S
First Degree AV Block
- Delay in conduction of the atrial impulse to the ventricles
- PR intervals remain constant
- If you can’t find P waves, search for P waves hidden in preceding T waves
- P-R intervals may be up to 600 ms long (15 mm!)
Second Degree Block Mobitz Type II
- Intermittent failure of conduction of P-waves
- The PR interval is constant, and may be normal or prolonged
Causes
- Left atrial enlargement
- Advanced age
- Degenerative or atherosclerotic conduction system disease
- Connective tissue disease (ankylosing spondylitis; HLA-B27)
- Inferior MI
- Medications: Nodal Blockade (e.g. b-blocker, verapamil, diltiazem, digitalis)
- Myocarditis (including Lyme disease)
- Aortic valve endocarditis (paravalvular abscess)
- Cardiomyopathies