Examination of the differential impacts of antitachycardia pacing vs. shock on patient activity in the EMPIRIC study

Implantable cardioverter defibrillators (ICDs) have demonstrated mortality advantages over antiarrhythmic drug therapy, but ICD shock has known detrimental effects on quality of life and psychologic functioning. However, it remains unknown how patient activity level is affected by shock, or by antitachycardia pacing (ATP), which was developed to reduce the treatment burden of shocks. Examine the differential impact of ICD shock and ATP on patient activity level as a novel way to capture the relative behavioural repercussions of these ICD therapies.

Accelerometer-derived activity data were analysed for a subset of patients (males = 83%; mean age = 62 years) enrolled in the EMPIRIC trial who received shock (n = 71) or ATP (n = 103). Differences in activity between a week pre-therapy and a week post-therapy were examined to assess the behavioural repercussions of shock vs. ATP when one, few (2–4), or many (5+) therapies were delivered. For patients receiving shock, a significant reduction in activity was observed for few (−26%) and many shocks (−34%) in the first week post-therapy (P < 0.05). In weeks 2–4, activity levels recovered towards baseline levels. In contrast, no level of ATP-only therapy significantly reduced patients' activity levels at any time following therapy.

This study is the first to evaluate objective, behavioural effects of shock, and whether these effects are comparable with ATP therapy alone. In tandem with existing literature, current results highlight that ICD shocks and ATP have divergent effects on behavioural outcomes, with ATP's effect profile in these domains appearing somewhat favourable.