Prevalence of cancelled shock therapy and relationship to shock delivery in recipients of implantable cardioverter-defibrillators assessed by remote monitoring.

BACKGROUND

Cancelled shock therapy (CxTx) may presage shock delivery and shorten battery longevity of implantable cardioverter-defibrillators (ICDs). However, it is silent and has received little attention. Remote home monitoring (HM) with continuous surveillance and automatic daily data archiving allows investigation of CxTx.

METHODS AND RESULTS

We retrospectively analyzed a database of 4,960 recipients of HM ICD, from 2002 to 2007. Over a mean follow-up of 445 +/- 253 days, CxTx occurred in 1,392 (28%) patients, mostly as single episodes (n = 1,120). However, 142 patients (10% of patients with CxTx, 2.9% of the whole ICD population) had >10 CxTx. CxTx was followed by shock delivery in 432 patients, in 239 (55%) of whom CxTx occurred >10 days prior to shock delivery. In 113 patients (26%), CxTx occurred in the 72-hour period preceding the shock. A single CxTx preceded the shock in 74 of these 113 patients, and only eight patients had >3 CxTx.

CONCLUSION

CxTx was highly prevalent in unselected ICD recipients, though the intraindividual density of episodes was low. In 2.9% of the overall population, the number of CxTx was sufficient to shorten the battery longevity. A high number of CxTx usually did not predict the delivery of shocks.