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Supernormal Conduction of the Right Bundle Branch

1970; Elsevier BV; Volume: 57; Issue: 4 Linguagem: Inglês

10.1378/chest.57.4.395

1931-3543

Michael J. Mihalick, Charlés Fisch,

Cardiomyopathy and Myosin Studies

The so-called “supernormal” phase is that portion of the recovery period of excitable cells during which a subthreshold stimulus may elicit a propagated response (ie, supernormality of excitability), or during which conduction of an oncoming impulse is facilitated to a greater degree than if it arrived earlier or later in the recovery cycle (ie, supernormality of conductivity). First described in nerves by Adrian and Lucas 1 Adrian E.D. Lucas K. On the summation of propagated disturbances in nerve and muscle. J Physiol. 1912; 44: 69 Crossref Scopus (44) Google Scholar in 1912, supernormality was demonstrated in cardiac tissue by Adrian 2 Adrian E.D. The recovery process of excitable tissues, Part I. J Physiol. 1920; 54: 1 Crossref PubMed Scopus (21) Google Scholar in 1920. Since that time, it has been demonstrated in the mammal 3 Fisch C. Steinmetz E.F. Supernormal phase of A-V conduction due to potassium A-V alternans with first degree A-V block. Amer Heart J. 1961; 62: 211 Abstract Full Text PDF PubMed Scopus (7) Google Scholar , 4 Hoff H.E. Nahum L.H. The supernormal period in the mammalian ventricle. Amer J Physiol. 1938; 124: 591 Google Scholar , 5 Linenthal A.J. Zoll P.M. Quantitative studies of ventricular refractory and supernormal periods in man. Trans Assoc Amer Physicians. 1962; 75: 285 PubMed Google Scholar and inferred for the human heart 6 Soloff L.A. Jewell J.W. The supernormal phase of ventricular excitation in man. Its bearing on the genesis of ventricular premature systoles, and a note on atrioventricular conduction. Amer Heart J. 1960; 59: 869 Abstract Full Text PDF Scopus (21) Google Scholar , 7 Pick A. Langendorf R. Katz L.N. The supernormal phase of atrioventricular conduction. Circulation. 1962; 26: 388 Crossref PubMed Scopus (33) Google Scholar , 8 Ashman R. Herrmann G.R. Supernormal phase of conduction and recovery curve for human junctional tissue. Amer Heart J. 1926; 1: 594 Abstract Full Text PDF Scopus (4) Google Scholar , 9 Hoffman B.F. Physiology of atrioventricular transmission. Circulation. 1961; 24: 506 Crossref PubMed Google Scholar , 10 Lewis N. Master A.M. Supernormal recovery phase, illustrated by two clinical cases of heart block. Heart. 1924; 11: 371 Google Scholar , 11 Luten D. Pope S II Variations in heart block sometimes attributed to a supernormal recovery phase. Amer Heart J. 1930; 5: 750 Abstract Full Text PDF Google Scholar by careful analysis of clinical tracings. Although from the surface tracings it is indeed impossible to separate supernormality of excitability and conduction, our discussion will be confined to supernormality of conduction (SNC). It must be emphasized that the state of conductivity reached during this period is never “supernormal” or better than normal, but only better than expected under the prevailing physiologic conditions. Indeed, SNC has only been demonstrated in depressed or diseased hearts. As evidence for its existence in the normal heart is lacking, this concept is challenged by some workers in this field. 12 Moe G.K. Childers R.W. Meredith J. An appraisal of “supernormal” A-V conduction. Circulation. 1968; 38: 5 Crossref PubMed Scopus (94) Google Scholar , 13 Seldman D.S. Excitability of the human heart on edocardial stimulation. Clin Res. 1963; 11: 166 Google Scholar