Abstract 2418: A Critical Analysis of Predisposing Factors of Inappropriate Shock in ICD Recipients
Despite rapid evolution of Implantable Cardioverter Defibrillator (ICD) devices and algorithms designed to reduce Inappropriate Shock Therapy (IST), IST remains a problem. Yet, existing reports on clinical predictors of IST focus on single-center studies with small samples, studying only rates and causes of IST. As a result, IST is difficult to predict and manage, posing significant clinical challenges. The purpose of this study was to examine predisposing factors of IST by exploring trigger events of IST.
METHODS: We analyzed the incidence and clinical predictors of IST in ICD recipients with a five-year retrospective review of ICD interrogation records and medical charts at a university hospital. A total of 119 charts were reviewed with identification of those experiencing IST. Clinical predictors of age, gender, NYHA class, ejection fraction (EF), and structural heart disease were analyzed by frequency, chi-square, logistic regression. The underlying aspects of trigger events were studied by incorporating events when IST occurred, and by correlating those with subjects’ clinical histories.
RESULTS: A total of 119 patients were enrolled in the study: 98 men and 21 women. Mean follow-up time was 24.1 ± 16.2 months. IST occurred in 13 of 119 ICD recipients (9%). A total of 16 IST episodes occurred among 13 patients, with the following triggers for IST: 8 atrial fibrillation(AF), 2 sinus tachycardia/normal sinus rhythm; 2 double counting; 1 lead problem; and 1 drug interaction. Using Chi-square and logistic regression analysis, results showed only AF as a significant predictor (p=.002 vs 0.001). Variables of age, gender, NYHA class, ejection fraction and structural heart disease showed no significant relationship. Review of patient histories revealed either baseline AF or multiple risk factors for AF. Further review isolated circumstances increasing the risk of IST, such as electrolyte imbalance, sinus tachycardia during exercise stress testing and missed doses of medication.
CONCLUSION: IST poses clinical challenges. AF was the most common precipitating factor in IST. The trigger events precipitating IST were varied in this study population, and their salience as clinical predictors of IST should be noted when planning clinical interventions.