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Atrioventricular Electrotonic Interaction in Complete Atrioventricular Block: An Experimental Model Using Radiofrequency Energy in the Rabbit Heart
Author(s) -
SANCHIS JUAN,
CHORRO FRANCISCO J.,
LÓPEZMERINO VICENTE,
SUCH LUIS,
AVELLANA JUAN A.,
MARTÍNEZMAS MARÍA LUZ
Publication year - 1991
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1991.tb06483.x
Subject(s) - beat (acoustics) , phase response curve , medicine , atrioventricular block , acceleration , cardiology , coupling (piping) , sinus rhythm , rhythm , phase response , nuclear magnetic resonance , phase (matter) , physics , atrial fibrillation , optics , circadian rhythm , mechanical engineering , circadian clock , classical mechanics , quantum mechanics , engineering
Provided the conditions for electrotonic transmission exist, an automatic focus surrounded by a block zone may be externally modu‐lated. The atrioventricular (AV) electrotonic interaction was studied in 16 perfused rabbit hearts with supra‐Hisian complete AV block induced using low radiofrequency energy doses (2.5 watts; 10 seconds). In nine experiments the sinus node was preserved (group I), whereas in seven it was removed maintaining an AV nodal rhythm (group II). The V‐V (ventricular cycle length) and V‐A (coupling of the intervening atrial beat) in both groups, and also the A‐A (atrial cycle length) and A‐V (coupling of the intervening ventricular beat) intervals in group II, were measured beat by beat after current delivery. The phase response curves V‐V versus V‐A, and A‐A versus A‐V showed AV interaction in five experiments from group I, and in four from group II, as follows: (1) accelerating phase response curve, characterized by a pacemaker acceleration (V‐V or A‐A abbreviation) at a critical V‐A or A‐V coupling interval; maximum acceleration could be progressively (phase response curve without rapid cross‐over) or briskly (phase response curve with rapid crossover) reached; from this point onwards acceleration decreased with a further increase in V‐A or A‐V coupling interval (acceleration slope). (2) Biphasic phase response curve, characterized by initial delaying and late accelerating phases. Maximum acceleration and the acceleration slope were both smaller in accelerating phase response curves without rapid cross‐over. On reverting complete block in two experiments, a progressive increase in maximum acceleration and acceleration slope was observed. Conclusions: (1) AV interaction in complete AV block can be manifested as accelerating or biphasic phase response curves; (2) transition from electrotonic interaction to conduction seems to be a continuum.