The minimal mass required for induction of a sustained arrhythmia averaged 32 mg in left atrial preparations and 28 mg in right atrial segments from rabbits, consistent with re-entry excitation.
The observed minimal mass required to sustain an arrhythmia in isolated rabbit atria aligns with theoretical requirements for re-entry excitation.
With the aid of electrical stimulation and a combination of acetylcholine and physostigmine, an experimental arrhythmia was predictably induced in isolated atrial segments from rabbits. The tissue was from either left or right atrium, but was not spontaneously active. It was driven electrically at the rate of 2/sec. After the measurement of excitability and of conduction time, both in the presence and absence of ACh, an arrhythmia was induced. The tissue then was divided surgically and the procedure repeated until a residual segment was obtained which did not respond with an arrhythmia. The weight of the nonarrhythmic segment was determined and averaged 32 mg in 16 left atrial preparations, 28 mg in 10 right atrial segments, and 38 mg in 4 segments of left atrium from rabbits chronically treated with reserpine. Calculation of the mean conduction time and of the mean refractory period associated with induction of the experimental arrhythmia indicated that the observed minimal arrhythmic segment was approximately the mass theoretically required if the initiation and maintenance of the arrhythmia were dependent on re-entry excitation.
West et al. (1962) studied Arrhythmia (n=30). Electrical stimulation with acetylcholine and physostigmine, followed by surgical division was evaluated on Minimal mass required for induction of a sustained arrhythmia. The minimal mass required for induction of a sustained arrhythmia averaged 32 mg in left atrial preparations and 28 mg in right atrial segments from rabbits, consistent with re-entry excitation.