Inappropriate shocks diagnosed by stored electrograms of implantable cardioverter defibrillators--two case reports

An implantable cardioverter defibrillator is an important therapeutic option for patients with high risk of life-threatening ventricular arrhythmias. However, their use is also associated with several complications including inappropriate shock. Although the most frequent cause of inappropriate shock is supraventricular tachyarrhythmias, lead fracture can also be associated with inappropriate shock. Diagnosis of lead fracture can be made by chest x-ray radiography, fluoroscopic examination, interrogation of the device, and intracardiac electrograms. In this report, the authors present two cases of inappropriate shock due to lead fractures in the costoclavicular region that could only be diagnosed by the help of stored intracardiac electrograms. Methods for diagnosis of lead fractures and modalities to avoid recurrences are also discussed.