Incidence and Clinical Predictors of Risk Factors for Inappropriate Shock in Patients with Implantable Cardioverter-Defibrillators

Sudden cardiac death (SCD) is a major unresolved medical problem worldwide. Although Implantable Cardioverter-Defibrillators (ICD) are highly effective in diagnosing and treating life threatening arrhythmias, inappropriate shock therapy (IST) occurs in approximately 5-20% of ICD recipients. IST results in pain, anxiety, induction of ventricular arrhythmias, decreased battery longevity, and even death. Researchers studying clinical predictors of IST have drawn findings based on single case studies with small samples or with outdated data. This study filled this gap by describing the incidence and co-existing clinical predictors of IST. Methodology This descriptive, retrospective study analyzed the incidence and clinical predictors of IST in ICD adult recipients by utilizing a five-year retrospective review ICD interrogation records and medical charts at a university hospital. Results During a mean follow-up period of 24.1 ± 16.2 months, 20 out of 119 ICD recipients received appropriate shock, and IST occurred in 13(9%) out of 119 ICD recipients. A total of 16 IST experiences occurred among these 13 patients. Eight subjects received IST for atrial fibrillation (AF)/atria tachycardia or sinus tachycardia/normal sinus rhythm, two for double counting, two for lead problems, and one for drug interaction. Of these, 12 out of 98 men received IST. One out of 21 women received IST. Using Chi-square and logistic regression analysis, results showed only AF as a significant predictor (p=.002 vs. 0.001) and remains the main cause of IST. Although the variables of age, gender, NYHA class LVEF and structural heart disease showed no significant relationship. Trigger events occurred during clinical interventions and were noted in this study. Conclusion The clinical characteristics of patients prone to IST should be carefully considered when planning clinical interventions. With the rapid expansion of this patient population, a multisite expanded longitudinal study is indicated to confirm the results seen in this initial descriptive study