Management of Patients with Frequent Appropriate and Inappropriate Implantable Cardioverter-Defibrillator Shocks

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Abstract

Implantable cardioverter–defibrilator (ICD) shock management is a growing part of cardiology practice. These shocks are associated with increasing mortality. Therefore, evaluation of the shocks and potential intervention is justified. This evaluation includes analysis of the cause of the shock and an intervention to decrease the risk for future shocks. Such management may include optimization of heart failure medication, addition of antiarrhythmic medications, or more invasive approaches including radiofrequency ablation and ICD system revisions.

Disclosure
Soraya M Samii, MD, PhD, is a consultant for Boston Scientific. Gerald V Nacarelli, MD, receives research grants from Boston Scientific, sanofi-aventis, and Boehringer Ingelheim, and is a consultant for GlaxoSmithKline, Medtronic, Boston Scientific, Pfizer, Xention, sanofi-aventis, Gilead, Novartis, Portola, AstraZeneca, Bristol-Myers Squibb, and Merck.
Correspondence
Gerald V Naccarelli, MD, Penn State Heart and Vascular Institute, PO Box 850, MC H047, Hershey, PA 17033-0850. E: gnaccarelli@hmc.psu.edu
Received date
16 June 2010
Accepted date
12 July 2010
Citation
US Cardiology - Volume 7 Issue 2;2010:7(2):34-36
Correspondence
Gerald V Naccarelli, MD, Penn State Heart and Vascular Institute, PO Box 850, MC H047, Hershey, PA 17033-0850. E: gnaccarelli@hmc.psu.edu

Pages

Patients presenting with implantable cardioverter–defibrillator (ICD) shocks are increasingly common, primarily due to the expansion of ICD-placement indications. The discomfort and pain associated with ICD shocks often result in immediate medical attention. This occurs in emergency rooms and as acute visits in doctor’s offices. With the advances in remote monitoring, these alerts can also occur as emails, faxes, and telephone calls. More importantly, patients who receive shocks from their ICD are at increased risk for death than those who receive no shock irrespective of whether the shock is appropriate or not. This measurable increase in mortality warrants further evaluation of patients who receive shocks. Patients with ICDs are expected to receive shocks. The risk for receiving an appropriate shock in the first one to three years is 20–35% in patients with left ventricular ejection fractions ≤35% who have had no evidence of sustained ventricular arrhythmias. Forty-five percent of patients with an ICD who have survived a cardiac arrest or have documented sustained ventricular arrhythmias will receive an appropriate shock within the first year after implantation. Inappropriate shocks account for about one-third of all shocks. The overall annual inappropriate shock risk for a patient with an ICD is estimated at 7.5%.1 Irrespective of the cause of the ICD shocks, patients also have increased morbidity, with anxiety, depression, and even post-traumatic stress response from multiple shocks. These consequences can lead to further functional decline in the patient and a decreased quality of life.2
Management of frequent shocks starts with determination of the cause of the shock. Is the shock from an artifact or an arrhythmia? Most frequently, the cause of an ICD shock is appropriate and secondary to ventricular arrhythmias. Despite the potentially life-saving shock, sustained ventricular arrhythmias are associated with increased mortality and morbidity. In the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) study group, patients had a three-fold increase in heart failure hospitalization and death after an appropriate shock.3 In the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), the risk for death was increased five-fold after an appropriate shock from the ICD.1 Antitachycardic pacing therapies have been shown in multiple studies to reduce shock number.4 This reduction in shock number by using antitachycardic pacing has recently been shown to correlate with reduced mortality in a retrospective analysis of >2,000 patients.5

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