Atrioventricular nodal re-entrant tachycardia (AVNRT)* is a supraventricular tachycardia caused by re-entry involving the atrioventricular node and its right atrial input pathways.
Mechanism and rhythm
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The re-entry circuit involves a superior fast pathway and an inferior slow pathway.
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AVNRT produces a regular tachycardia at 120–240/min and tends to occur without structural heart disease.
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Episodes may last from a few seconds to many hours.
Clinical features
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Patients usually notice a rapid, very forceful, regular heartbeat; chest discomfort, lightheadedness and breathlessness may occur.
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Polyuria sometimes occurs, mainly because of ANP release.
Electrocardiographic findings
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The electrocardiogram usually shows tachycardia with normal QRS complexes.
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A notch in the terminal QRS complex in lead V1 may produce a pseudo R′.