Junctional tachycardia is a narrow complex supraventricular tachycardia characterized by electrical impulse generation from theAV node that is independent of or dissociated from that of the sinoatrial node (SA node) at a rate > 60 beats per minute.

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Normally, the atrioventricular node (AVN) can generate an escape rhythm of 40-60 beats per minute in case the sinoatrial node(SA node) or atrial pacemakers fail (sinus arrest) or slow (sinus bradycardia) or if there is complete heart block. Thisjunctional escape rhythm generates a normal, narrow QRS complex rhythm at a rte below 60 beats per minute (junctional bradycardia) as the electrical impulses once they are generated are conducted with normal velocity down the His-Purkinje system. Retrograde P waves (i.e. upside down) due to retrograde or backward conduction may or may not be present in junctional bradycardia.

In contrast to a junctional escape rhythm or junctional bradycardia at a rate of 40-60 beats per minute, junctional tachycardia is faster, at a rate > 60 beats per minute. Junctional tachycardia generates a normal, narrow QRS complex rhythm as the electrical impulses are conducted with normal velocity down the His-Purkinje system. Retrograde P waves (i.e. upside down) P waves due to retrograde or backward conduction may or may not be present.

The cause of the more rapid firing of the atrioventricular node is thought to be due to enhanced automaticity as a result of abnormal Calcium metabolism in the sarcoplastic reticulum.^[1]

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Junctional tachycardia may oocur either as a result of enhanced automaticity of the AV node when the SA node is bradycardic or discharges at a slower rate than the AV node (e.g. myocardial infarction, digitalis toxicity) or when an ectopic focus with an abnormal automaticity develops within or adjacent to the AV junction. Other causes include: hypoxia, electrolyte imbalance, and infections such as rheumatic fever, Lyme disease.

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Digitalis toxicity
• Hypokalemia
• Hypothermia
• Lithium toxicity
• Myocardial infarction

• Beta blockers
• Cardiac surgery
• Digitalis toxicity
• Hypokalemia
• Hypothermia
• Hypoxia
• Myocardial infarction
• Pericarditis

Junctional tachycardia causes developed by WikiDoc.org

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• Sinus tachycardia:
• Atrioventricular nodal reentrant tachycardia: It can appear similar to atrioventricular nodal reentrant tachycardia.^[1]

One form is junctional ectopic tachycardia.

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Males and females are affected equally.

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