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Management of ICD Shocks

A single shock in the absence of any symptoms does not require investigation.

Clinical evidence that implantable cardioverter defibrillators (ICDs) reduce mortality has led to a significant increase in their use. However, shocks — whether appropriate (e.g., for ventricular tachycardia) or inappropriate (e.g., for supraventricular tachycardia) — diminish physical and psychological well-being. These authors reviewed the literature and scientific guidelines to assess the management of patients who have experienced one or more ICD shocks.

Causes of inappropriate shocks were found to include misinterpretation of cardiac rhythms, lead failure, and over-sensing of T-waves and diaphragmatic myopotentials. The authors advise that a single shock not associated with cardiac symptoms does not require emergent evaluation. In such cases, patients should be reassured and referred to a clinical electrophysiologist within 1 week. If cardiac symptoms are present or multiple shocks have occurred, the clinician should assess the patient immediately for myocardial ischemia, congestive heart failure, electrolyte abnormalities, or medication noncompliance. If no cause is found, the ICD should be interrogated by an electrophysiologist, who may consider optimizing ICD programming, prescribing antiarrhythmic medication, or both.

Comment: Emergency physicians frequently encounter patients with ICDs who have experienced one or more shocks. This review of high-grade evidence offers a sensible approach. A single ICD shock in a patient without cardiac symptoms does not warrant immediate investigation. If multiple shocks have occurred or the clinical story is worrisome, emergent investigation, interrogation, and, possibly, therapy are indicated.

— John A. Marx, MD, FAAEM, FACEP

Published in Journal Watch Emergency Medicine January 19, 2007

Citation(s):

Gehi AK et al. Evaluation and management of patients after implantable cardioverter-defibrillator shock. JAMA 2006 Dec 20; 296:2839-47.

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