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.[1] 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)