Slow anterograde conduction through an anomalous pathway in a case of complete atrioventricular block in the normal pathway

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Abstract

Conduction through anomalous pathways (AP) works according to tile an or none law; it means that it would not be possible decremental or slow conduction in it. However, in a sick AP, these law may have exceptions, that occurs in a patient with Chagas' cardiomyopathy, complete AV block in the His-Purkinje system and type B WPW syndrome with lrst degree AV block. Valsalva manoeuvre produced isolated P waves block, 4 = 2 Mobitz II type second degree AV block and brief runs of phase 3 paroxysmal AV block. Increasing rate atrial overdriving (AO) caused progressive AV conduction impairment, with Wenckebach periodicities, AV block 2=1, 3=1 and phase 3 paroxysmal AV block. When atrial extrastimulus plus AO was performed, there was a loss of the normal phenomenon of "rate accomodation", with fatigue. Verapamil produced third degree AV block and lidocaine, 3= 1 AV block. Since the patient had a complete and permanent AV block in their His-Purkinje system, all the conduction disturb- ances are do to occur in the sick, slow conducting anomalous pathway.