Atrioventricular block

Prolongation of the electrocardiographic PR interval referred  to a first-degree atrioventricular block.

AV block is defined as a pathologic delay or interruption in the conduction of electrical impulses traveling from the sinus node to the ventricles.

First-degree block has a PR interval of greater tan 200 milliseconds.

PR interval is determined by the conduction time from the sinus node to the ventricles.

First-degree atrioventricular block may be secondary conduction delay in the atrium, the atrioventricular node, and/or His Purkinje system.

The atrioventricular node is the site most frequently involved in adults, although more than 1 site of conduction delay may be present.

Causes of first-degree atrioventricular block include: ischemic heart disease, degenerative conduction system disease, connective tissue disease, congenital heart disease, inflammatory disease and various medications.

First-degree AV block typically present in ambulatory patients in the absence of acute cardiovascular disease.

First-degree block associated with increased risk of atrial fibrillation, mortality and subsequent pacemaker implantation (Cheng S).

Complete AV block occurs when there is complete absence of conduction from the sinus node to the ventricles.

Causes of AV block are variable: fibrosis and ischemic heart disease are the most common.

Cardiac pacing is the standard of treatment for high-grade block.

Single-chamber or dual-chamber pacing have similar rate of cardiovascular events during the first three years after implantation of the pacemaker.

The type of pacing in elderly patients with high-grade A-V block does not influence the death rate from all causes during the first three years following pacemaker implantation.

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