Abstract 10326: Inappropriate Shocks in MADIT-CRT: Predictors and Outcome
BACKGROUND: ICD patients commonly experience inappropriate therapy (IT) including inappropriate shocks (IS). IS were associated with an increase in the risk of mortality in MADIT II and SCD-HeFT, but whether this would pertain in MADIT-CRT's less symptomatic HF population (NYHA I-II) is unknown. Early cardiac resynchronization therapy (CRT) devices suffered from double-counting of RV and LV activations, but the relative incidence of IT or IS in ICD and modern CRT devices is unknown. We evaluated the incidence of IT and IS in ICD versus CRT in MADIT-CRT. We further assessed whether the mortality rate was increased following IS or IT.
Methods: Committees adjudicated HF and ICD events (appropriate vs inappropriate).
RESULTS: The IS event rate was not different in ICD vs CRT (Figure). At 3-years the IT event rate was 14% and 13% in ICD and CRT arm patients respectively. SVT was the most common reason for IT, followed by AF then abnormal sensing. Using multivariate analysis, predictors of IT included age over 65, enrollment at non-US center, and absence of statin therapy; IS predictors on the other hand were age, prior hospitalization and absence of statin therapy. Patients experiencing IT or IS were more likely to experience a HF event, but after adjustment for covariates, including appropriate therapy, neither HF/death nor death alone was associated with IT or IS. Appropriate therapy, on the other hand, was associated with a nearly twofold higher risk of either the composite event of HF or death or death alone. When analyzed separately, ischemic HF patients who experienced IT were 3.3 times as likely to die (p=0.008) and ischemic IS recipients had a trend toward more HF or death events (HR 1.97, CI 0.91-4.26, p=0.083).
CONCLUSIONS: IT and IS occurred with similar frequency in the ICD and CRT arms. Overall, patients experiencing IT or IS were not more likely to experience HF or death, although the subgroup of patients with ischemic HF tended to have worse outcomes after IT or IS.
- © 2011 by American Heart Association, Inc.