Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 53, Num. 2, 2007, pp. 148-149

Journal of Postgraduate Medicine, Vol. 53, No. 2, April-June, 2007, pp. 148-149

Letters

Blocked or delayed atrioventricular nodal conduction due to concealed conduction due to interpolated ventricular ectopics

Udyavar AR, Pandurangi UM

Department of Cardiology, Institute of Cardiovascular Disease, Madras Medical Mission, 4A, Dr. JJ Nagar, Mogappair, Chennai - 600 037
Correspondence Address:Department of Cardiology, Institute of Cardiovascular Disease, Madras Medical Mission, 4A, Dr. JJ Nagar, Mogappair, Chennai - 600 037, drameya@gmail.com

Code Number: jp07053

Sir,

Concealed conduction commonly occurs when an interpolated premature ventricular impulse enters the His Purkinje system and atrioventricular (AV) node retrogradely but does not reach the atrium. As a consequence, the ensuing sinus impulse either does not conduct to the ventricle or conducts with a prolonged PR interval due to the increased AV nodal refractoriness. This effect of the extra-systole on AV conduction of the next sinus impulse should not be misdiagnosed as an AV block.[1] We report the case of a 20-year-old gentleman who was referred for palpitations at rest. We advised him a 24h Holter monitoring for further workup. Some Holter strips are shown in [Figure - 1].

The top strip reveals interpolated ventricular extra-systoles in bigeminal rhythm with prolonged PR interval in sinus beats that follow the premature complexes. The same phenomenon occurs in the middle strip, but here sinus beats that closely follow the premature ones undergo a progressive PR interval prolongation ending in the block of a sinus impulse (the third sinus P wave).

The bottom strip of [Figure - 1] again reveals interpolated ventricular ectopics (PVCs) occurring in bigeminal rhythm; due to the effect of retrograde concealed penetration of the PVC into the AV junction, the ensuing sinus impulses are alternatively conducted and blocked. The concept of concealed conduction was introduced by Langendorf.[2] The term was applied whenever penetration of an impulse into a defined cardiac structure was not immediately evident at the surface electrocardiogram, but could only be recognized by its after effects on formation or conduction of the ensuing impulse. The definition of concealed conduction has been irrevocably altered by the availability of intracardiac recordings,[3] that may, at times, directly demonstrate the conduction of an impulse into a defined cardiac structure, despite this not being evident at the surface ECG. Although the AV node is the site most commonly associated with concealed conduction, this phenomenon can occur in any section of the heart.[3]

Concealed conduction often occurs when a PVC enters the His Purkinje system and the AV node retrogradely but does not reach the atrium. As a consequence, the next sinus impulse either does not conduct to the ventricle or conducts with PR interval prolongation.[1] The present case demonstrates how interpolated PVCs can have totally different effects on AV nodal conduction of the ensuing sinus impulse as a result of different patterns of concealed retrograde conduction. These patients should not be misdiagnosed as having advanced AV block.[4],[5]

References

Copyright 2007 - Journal of Postgraduate Medicine

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