Nature of the Gap Phenomenon in Man

The atrioventricular (AV) gap phenomenon occurs when the effective refractory period of a distal site is longer than the functional refractory period of a proximal site and when closely coupled stimuli are delayed enough at the proximal site to allow distal site recovery. According to previous studies, in type 1 gap, the distal site of block is distal to the His bundle (ventricular specialized conduction system) and the proximal site of block is in the AV node. In type 2 gap, both the proximal and the distal sites of conduction block are within the ventricular specialized conduction system. Using His bundle recordings and atrial extra-stimulus techniques in man, we observed three previously undescribed types of gaps between (1) the AV node (distal) and the atrium (proximal), (2) the His bundle (distal) and the AV node (proximal), and (3) the ventricular specialized conduction system or a bundle branch (distal) and the His bundle (proximal). The delays at the His bundle in the second and third types of gaps seen in this study were demonstrated as splitting of His bundle potentials. Gaps between the AV node or the His bundle and the ventricular specialized conduction system were more easily demonstrated at long cycle lengths, but gaps between the atrium and the AV node were more easily demonstrated at short cycle lengths. Therefore, the previous subdivision of gaps into two types is an oversimplification, because gaps can occur between multiple sites in the conduction system. The gap phenomenon may be potentiated by both long and short cycle lengths; long cycle lengths increase the effective refractory period of a distal site, e.g., the His bundle and the ventricular specialized conduction system, and the short cycle lengths decrease the functional refractory period of a proximal site, e.g., the atrium and the AV node.

[1]  P. Denes,et al.  The Effects of Cycle Length on Cardiac Refractory Periods in Man , 1974, Circulation.

[2]  J. Kupersmith,et al.  Conduction Intervals and Conduction Velocity in the Human Cardiac Conduction System: Studies during Open‐Heart Surgery , 1973, Circulation.

[3]  A. Castellanos,et al.  Type I, Type II, and Type III Gaps in Bundle‐Branch Conduction , 1973, Circulation.

[4]  M. Josephson,et al.  Gap in A-V conduction in man; types I and II. , 1973, American heart journal.

[5]  T. Sano,et al.  Nature of His potential in His electrogram. , 1972, Japanese heart journal.

[6]  B. Scherlag,et al.  Atrioventricular block: Localization and classification by his bundle recordings , 1971 .

[7]  B F Hoffman,et al.  Functional Characteristics of the Gating Mechanism in the Canine A‐V Conducting System , 1971, Circulation research.

[8]  K. Rosen,et al.  Bundle Branch and Ventricular Activation in Man: A Study Using Catheter Recordings of Left and Right Bundle Branch Potentials , 1971, Circulation.

[9]  A. Damato,et al.  Phenomenon of the Gap in Atrioventricular Conduction in the Human Heart , 1970, Circulation research.

[10]  K. Rosen,et al.  Patterns of Atrioventricular Conduction in the Human Heart , 1970, Circulation research.

[11]  A. Damato,et al.  Catheter Recording and Validation of Left Bundle‐Branch Potentials in Intact Dogs , 1970, Circulation.

[12]  B F Hoffman,et al.  Electrophysiological Properties of the Canine Peripheral A‐V Conducting System , 1970 .

[13]  B J Scherlag,et al.  Catheter Technique for Recording His Bundle Activity in Man , 1969, Circulation.

[14]  J. Bigger,et al.  Spontaneous and induced reentrant tachycardia. , 1969, Annals of internal medicine.

[15]  D. Durrer.  Electrical aspects of human cardiac activity: a clinical-physiological approach to excitation and stimulation. , 1968, Cardiovascular research.

[16]  G. Moe,et al.  Aberrant A‐V Impulse Propagation in the Dog Heart: A Study of Functional Bundle Branch Block , 1965, Circulation research.