Tetanizing prepulse: A novel strategy to mitigate implantable cardioverter-defibrillator shock-related pain

Skeletal muscle activation has been implicated as the source of pain associated with implantable cardioverter-defibrillator shocks. We hypothesized that the skeletal muscle response to defibrillatory shocks could be attenuated with a tetanizing prepulse immediately before biphasic shock delivery.

The purpose of this study was to test the ability of tetanizing prepulses to reduce the skeletal muscle activation associated with defibrillation.

Seven adult pigs were studied. A left ventricular coil and subcutaneous dummy can in the right thorax were used to deliver either pure biphasic waveforms or test waveforms consisting of a tetanizing pulse of high-frequency alternating current (HFAC) ramped to an amplitude of 5-100 V over 0.25-1 second, immediately followed by a biphasic shock of approximately 9 J (ramped HFAC and biphasic [rHFAC+B]). We used limb acceleration and rate of force development as surrogate measures of pain. Test and control waveforms were delivered in sinus rhythm and induced ventricular fibrillation to test defibrillation efficacy.

Defibrillation threshold energy was indistinguishable between rHFAC+B and pure biphasic shocks. Peak acceleration and rate of force development were reduced by 72% ± 7% and 71% ± 22%, respectively, with a 25-V, 1-second rHFAC+B waveform compared with pure biphasic shocks. Notably, rHFAC+B with a 9-J biphasic shock produced significantly less skeletal muscle activation than a 0.1-J pure biphasic shock.

A putative source of implantable cardioverter-defibrillator shock-related pain can be mitigated using a tetanizing prepulse followed by biphasic shock. Human studies will be required to assess true pain reduction with this approach.