Permanent Junctional Reciprocating Tachycardia
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PresentationThis may present in the neonatal period with heart failure due to tachycardia induced cardiomyopathy or in early childhood with either heart failure or palpitations. It is usually incessant tachycardia with very few periods of sinus rhythm. The rate is variable but usually slower than AVRT with a mean of 170 -180 bpm. When slow it may appear to be a sinus tachycardia except for the unusual p wave morphology. |
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MechanismIt is an AV re-entry tachycardia and the underlying mechanism is as for AVRT. It differs in that the accessory pathway in the postero-septal position and has a very long retrograde conduction time. Antegrade conduction and hence a delta wave are not seen. |
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ECGThe retrograde atrial activation is late and hence the P waves appear prior to the next QRS complex - the RP interval is therefore greater than the PR interval in contrast to AVRT. The 12 lead ECG pattern is characteristic with narrow p waves, negative in II, III, aVF and positive in V1 lying mid way between QRS complexes. |
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The tracing demonstrates 3 SVT beats with inverted p waves. There is a break in tachycardia of 2 sinus beats (with normal p wave morphology) then resumption of tachycardia. |
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ManagementThis arrhythmia can usually be controlled with flecainide or amioderone and reduce the rate sufficiently to reverse the cardiomyopathy. Radiofrequency ablation is then usually undertaken when the child is bigger although there are increasing reports of successful radiofrequency ablation in drug resistant cases in infancy. |
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PrognosisProvided radiofrequency is successful the long term outcome is now excellent. |
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This page was last edited 14/2/2004 |
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