Internal Defibrillation: Pain Perception of Low Energy Shocks

Abstract

Recently, device-based low energy cardoversion shocks have been used as therapy for AF. However, discomfort from internal low energy electrical shocks is poorly understood. The aim of this study was to evaluate pain perception with low energy internal discharges. Eighteen patients with ICD devices for malignant ventricular arrhythmias were recruited to receive shocks of 0.4 and 2 J in the nonsedated state. Discharges were delivered in a blinded, random order and questionnaires were used to determine discomfort levels and tolerability. Patients perceived discharges at these energies as relatively uncomfortable, averaging a score of 7.3 on a discomfort scale of 0-10, and could not distinguish 0.4-J shocks from 2-J shocks. Second shocks were perceived as more uncomfortable than initial discharges, regardless of the order in which the shocks were delivered. Despite the perceived discomfort, 83% of patients stated that they would tolerate discharges of this magnitude once per month, and 44% would tolerate weekly discharges. Patients perceive low energy discharges as painful and cannot distinguish between shocks of 0.4 and 2 J. The results suggest that ICD systems developed to treat atrial tachyarrhythmias should minimize the number of shocks delivered to terminate an atrial tachyarrhythmia episode. The majority of the patients tolerated low energy shocks provided the discharges are infrequent (once per month).

Psychophysiologic and Affective Parameters Associated With Pain Intensity of Cardiac Cardioverter Defibrillator Shock Discharges

“…This finding is in line with several other studies showing that a second delivered intracardiac shock is generally perceived as more uncomfortable than the first one, even when the second shock was delivered with less energy (13)(14)(15). Repetitive delivery of shocks also enhances the amplitude of startle responses in nonhuman (29,30) and human subjects (31) and may lead to sensitization in particular in ICD patients (32).…”

“…Nevertheless, the strength of the perceived pain among the ICD patients assessed in the present study varied considerably over the entire value spectrum of the 100-point VAS scale. Consistent with data from other studies dealing with pain from extreme short duration, these findings prove that a nociceptive stimulation resulting from the heart and the perceived pain intensity are only poorly correlated (11)(12)(13)(14)(15). What makes subjects perceive the same amount of nociceptive stimulation as unbearable on the one hand or almost not perceived on the other hand?…”

“…In the first place, characteristics of shock discharge, mainly the cumulative effect of repetitive shock delivery, may account for the degree of perceived pain intensity (13)(14)(15). However, reasons for this phenomenon have not been sufficiently elucidated so far.…”

Innovations in Clinical Cardiac Electrophysiology: Challenges and Upcoming Solutions in 2018 and Beyond

“…While the threshold for pain with ICD shocks is suggested to be o 0.1 J, 27 other commonly cited articles provide unconvincing evidence that shocks o 0.1 J are perceived as painless. [28][29][30][31] Current approaches to reducing DFTs, while promising, have not consistently reduced DFTs lower than this 0.1 J threshold.…”

Optimal Programming of Implantable Cardiac-Defibrillators

“…High-energy shocks are more likely to be successful for VT/VF and SVT (in case of inappropriate therapy) without any appreciable increase in patient discomfort or increase in charge time in contemporary devices. 60 Low-energy shocks also convey a risk of conversion of VT to VF. Hence, maximal shock strength is generally preferred.…”