Novel Insights Into the Role of the His-Purkinje System During Electrophysiologic Mapping of the Canine Heart in Ventricular Fibrillation

Aims: Ventricular fibrillation (VF) is the leading cause of death in the United States, responsible for 400,000 deaths each year. This lethal cardiac arrhythmia has been traditionally characterized as a disorder with marked rapid and erratic electrical impulses throughout the heart. The His-Purkinje system has been well studied as harboring potential triggers for the initiation of VF. However, the cardiac substrate responsible for VF maintenance remains relatively elusive. We hypothesized that regions of the His-Purkinje system are important in maintaining VF rhythm. We sought to test this hypothesis by electrophysiologic mapping of the canine heart during VF.

Methods and Results: We performed electrical mapping in VF on canines that were euthanized via electrical current to the right and left ventricles and on the epicardium. A standard EP recording catheter was used to collect local electrogram signals throughout the canine heart, both endo- and epicardially. Each anatomic location was analyzed to evaluate for changes in amplitude, cycle length, slew, and overall electrogram regularity.

We demonstrated feasibility of EP catheter mapping of VF in post-mortem canines. Our data supports a transmural gradient of rhythm regularity from the endocardium versus the epicardium (p=0.00009). Our data also support the presence of an intramural gradient in cycle length and regularity between the distal and proximal Purkinje systems (p=0.03).

Conclusions: This study is supportive of an integral role of the Purkinje system in the maintenance of VF. These early canine data merit further study to assess for the role of distal conduction in maintenance of VF, specifically ablation and modification of this substrate, in order to assess perturbation in VF sustainability.