Clinical Electrophysiology -> Ventricular Arrhythmias -> Physiology-Pharmacology D-PO01 - Featured Poster Session (ID 11) Poster

Abstract

Background: The Purkinje system represents a major source of ectopy initiating ventricular fibrillation (VF) in patients with structurally normal hearts. Under physiological conditions the Purkinje network is incapable of sustaining reentry. Significant conduction alterations within the Purkinje system are required for reentry to occur.
Objective: To characterize the incidence of inducible Purkinje repetitive activities (PRA) in patients who have survived unexplained sudden cardiac death (SCD).
Methods: We included 54 consecutive patients who survived SCD. Patients underwent extensive evaluation including MRI, pharmacological tests and high density invasive endocardial and epicardial mapping to identify VF substrate. Programmed ventricular stimulation was performed from the right (RV) and left ventricular (LV) apex. Each programmed extra-stimulation cycle (PEC) included a train at 600 or 400ms (S1) with up to 3 extrastimuli (S2, S3, S4). LV distal Purkinje potentials were recorded using a decapolar catheter. PRA was defined as the induction of ≥ 3 consecutive ventricular beats preceded by Purkinje potentials at cycle length ≤ 250ms. Bundle branch reentry was excluded when fascicular potentials were dissociated or absent confirming the distal origin of the Purkinje activity.
Results: A group of six patients (mean age 29 years, 5 females) presented with no identified substrate. PRA was induced with 48/607 (8%) PECs in this group leading to sustained VF in 4 cases. A mean of 5 (range 1-17) PRA sequences were recorded per patient. PRA was induced with 2 or 3 extrastimuli (S2= 0, S3= 11/227, S4= 37/199, P<0.001) and was more frequent with LV pacing (LV= 36/282 vs RV= 12/277, p=0.001). The mean number of consecutive Purkinje beats was 5.8 (range 3-31) and was not related to the pacing site (LV= 6.1 vs RV= 4.7, p=0.38) or to the number of extrastimuli (2 extra= 4.2 vs 3 extra= 6.2, p= 0.23).
Conclusion: Repetitive activity within the peripheral Purkinje system can be induced in a subset of survivors of VF with no other identifiable substrate. Provided confirmation in an ongoing control group, it may indicate genetic or acquired abnormality of Purkinje conduction which can underlay sudden death in this population.
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