First degree AV block causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Raviteja Guddeti, M.B.B.S. [3]
Overview
An atrioventricular block (or AV block) is a type of heart block involving an impairment of the conduction between the atria and the ventricles of the heart. It usually involves the atrioventricular node, but it can involve other structures too. AV block is categorized according to the degree and the site of conduction block. In first-degree AV block, all atrial impulses are conducted to the ventricles; however, there is a delay in conduction within the AV node resulting in a prolonged PR interval on ECG (>200 msec or >5 small blocks). In other words, first degree block is a slowed conduction without loss of atrioventricular synchrony.
Causes
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
Common Causes
- Hyperkalemia
- Hyperthyroidism
- Increased vagal tone (e.g. sleep, athletes)
- Ischemic heart disease
- Medications ( e.g. adenosine, amiodarone, beta-blockers, diltiazem, procainamide, verapamil)