CASE REPORTS Re-entry due to Manifest and Concealed

SUMMARY Concealed (C) His bundle ectopic systoles (H') have been shown in man to give rise to first and second degree atrioven-tricular (A-V) block and to simulate nonconducted atrial premature beats (P'). This report outlines a hitherto undescribed electro-physiologic consequence of H ' in a 69-year-old man with arterio-sclerotic heart disease and a Wenckebach type second degree A-V block in the His-Purkinje system. During a His bundle study, H' were shown to conduct either to the atria and ventricles with varying relationships to P ' and QRS, or to conduct only to the atria, IN 1947, LANGENDORF AND MEHLMAN ' utilizing deductive analysis of the electrocardiogram (ECG) suggested that concealed junctional premature systoles could simulate first and second degree heart block and non-conducted atrial premature beats. Langendorf and Langen-dorf and Pick3 later proposed that concealed junctional premature systoles could also result in alternation of the P-R interval and pseudo-Wenckebach periods. However, it was not until 1970, when Rosen and associates,4 through recording of the His bundle electrogram, provided the first documented example of concealed His bundle ectopic systoles producing intermittent first and second degree atrio-ventricular (A-V) block. Damato and colleagues5 showed, in an experimental model, that induced His bundle extra-systoles could simulate first and second degree A-V block, high degree A-V block, nonconducted atrial bigeminal rhythm, and alternation of the P-R interval. Few clinical ex-amples6- " proved the probability of some of these ex-perimental observations. The present report extends further the observations on electrophysiologic manifestations of His bundle ectopic systoles by describing a case in which both manifest and concealed His bundle ectopic systoles could ini-tiate a re-entrant arrhythmia. A critical analysis of the con-duction characteristics of the re-entry circuit strongly suggests retrograde conduction through an accessory pathway and antegrade conduction through the A-V node