Defibrillation shocks produce different effects on purkinje fibers and ventricular muscle: Implications for successful defibrillation, refibrillation and postshock arrhythmia

Abstract

These results indicate that high voltage shocks induce different responses in Purkinje fibers and ventricular muscle. The shock-induced rapid firing in the Purkinje fiber may contribute to postshock arrhythmias and possibly refibrillation in some cases. The shock-induced transient refractory state in the ventricular muscle may prevent the ventricle from responding to the rapid firing and thus may decrease the incidence of postshock arrhythmias.

Transmural and endocardial Purkinje activation in pigs before local myocardial activation after defibrillation shocks

“…Isolated papillary muscle studies have shown that Purkinje fibers are more sensitive to large shocks than is the working myocardium, and that they fire rapidly after exposure to a large shock. 10 This rapid firing may lead to multiple wavefronts on the heart at one time, which may degenerate back into VF. 11 While mapping studies have demonstrated that first myocardial activation emerges from the low field gradient region after near DFT shocks, 31,32 activation could originate in the conduction system in high gradient areas from rapidly firing Purkinje fibers and then spread to the low gradient areas.…”

“…Isolated preparations of canine Purkinje fibers demonstrated a dramatic increase in automaticity after defibrillation shocks, while cardiomyocytes demonstrated an increased refractory period. 10 The role of the specialized conduction system in the success or failure of defibrillation shocks is not known. The possibility exists that the specialized conduction system could be active during this period, but has not previously been reported.…”

Purkinje-mediated Effects in the Response of Quiescent Ventricles to Defibrillation Shocks

“…31 Electrophysiological properties of PS cells are distinct from those of ventricular myocytes, with prominent variations in numerous ionic currents. [16][17][18] The response of PS fibers to electrical fields differs from that of the endocardium upon which they run due to cellular differences 24 and because they are oriented in different directions than the myocardial fibers. Since the PS is a network of one-dimensional cables, they are also more prone to field excitation than threedimensional tissue.…”

Atria are more susceptible to electroporation than ventricles: Implications for atrial stunning, shock-induced arrhythmia and defibrillation failure

“…However, despite significant improvement in defibrillation efficacy, which has resulted in a radical reduction of defibrillation thresholds and myocardial damage, there is still extensive clinical and basic electrophysiology data indicating that defibrillation shocks are accompanied by adverse effects: (1) transient ectopy, tachycardia or reinduction of VF (1)(2)(3)(4)(5) and AF;(6) (2) bradycardia, complete heart block and increased pacing thresholds;(4;7;8) (3) atrial and ventricular electrical and mechanical dysfunction (stunning), which is directly related to the strength of shocks. (9)(10)(11)(12)(13)(14)(15)(16)(17) These effects are likely to be associated with shock-induced electroporation which is characterized by the formation of aqueous pores in the cellular lipid matrix.…”