VALUE OF TESTING THE DEFIBRILLATION FUNCT ION OF ICDS

Postoperative tests of implantable cardioverter defibrillators (ICDs) are routinely performed to ensure appropriate defibrillation by the de vice. However, efficacy and complications of this procedure are unknow n. To scrutinize the currently accepted indications to test the defibr illation function of the ICD we retrospectively analyzed 844 ICD-tests in 439 ICD-systems and 409 patients. 755 ICD-tests (89.4%) were routi nely performed (57% before discharge and 43% during follow-up); 58 tes ts (6.9%) were performed after a change of the antiarrhythmic drug reg imen, 24 tests (2.9%) after a revision of a part of the ICD-system, an d seven tests (0.8%) because of a suspected dysfunction of the ICD. Du ring routine-tests six ICD-systems (0.8%) failed to defibrillate the p atient. However, in all but one test abnormalities of the ICD-system h ad been observed before the test. After addition of antiarrhythmic dru gs, three of 58 ICD-systems (5.2%) failed to defibrillate the patient during the test (amiodarone: n = 2, flecainide: n = 1). Four of seven ICD-systems (57%) tested due to a suspected dysfunction failed to defi brillate the patient. After revisions of parts of the ICD-system, ICD- tests never revealed a failure of defibrillation. During 16 ICD-tests (1.9%) complications occurred. The most frequent complication was inap propriate shocks (n = 10; 1.2%), the most severe one (transient) neuro logic symptoms (n = 4; 0.48%). Our experience demonstrates that postop erative tests of the defibrillation function of ICDs rarely reveal ICD -dysfunction. As testing is unpleasant for the patient and not free of complications, tests might be restricted to those patients in whom an ICD-dysfunction is suspected (based on clinical presentation, results of chest-x-ray, testing of sensing signal and stimulation threshold) or class I or class III antiarrhythmic drugs have been added to the an tiarrhythmic drug regimen.