LETTERS TO THE EDITOR
Defibrillation thresholds testing of implantable cardioverter-defibrillators at implantation
Bharat K. Kantharia, MD, MRCP, FACC, FESC
Division of Cardiac Electrophysiology, Albert Einstein Medical Center, 5501 Old York Road, Philadelphia, PA 19141
(Email: kanthariab{at}einstein.edu).
I read with interest the reports on defibrillation testing (DFT) during implantable cardioverter-defibrillator (ICD) implantation published recently in JACC (1,2). There is a significant, albeit low, risk to serious complications including death during DFT testing. If the implantation data as measured through the device are satisfactory, then should we induce ventricular fibrillation (VF) in a patient who has poor cardiac function? Should we crash a brand new car during its "test-drive" to see whether the airbags will deploy? The following cases, which are mere examples, demonstrate the professional and moral dilemma of DFT testing.
Two patients with severe cardiomyopathy underwent ICD implantation with excellent parameters. In the first case, during DFT testing, first shock to provide a 10-J safety margin and a subsequent maximum output shock failed to defibrillate. External defibrillation restored sinus rhythm but with severe electromechanical dysfunction requiring emergent placement of a ventricular assist device and subsequently a heart transplantation. Was cardiomyopathy in itself responsible for the ICD failure? Did the shocks cause electromechanical dysfunction? Could the patient have survived an out-of-hospital VF episode? Did DFT testing identify deficiencies at implant? In the second case, DFT testing was not performed because of the presence of atrial fibrillation, suboptimal anticoagulation profile, and evidence of sludge in the left atrial appendage by a transesophageal echocardiogram. Elective cardioversion and DFT testing after six weeks of anticoagulation was planned. Unfortunately, in the interim period, the patient met with an unnatural mode of death. Subsequently, the patient's wife reported that "it may not mean much ... but the defibrillator did go off ... many times ... it did work ... when my husband died. ..."
During automobile accidents the airbags drastically reduce morbidity and mortality, but there is also a spectrum of injuries associated with them (3,4). Taking the analogy of the airbags and the ICDs, both of which reduce fatalities, perhaps in the case of the first patient, the "airbag" in itself was not adequate to prevent the fatality and, if anything, perhaps caused "airbag"-associated injuries. In the case of the second patient, the "airbag" deployed appropriately but could not prevent a non-road-traffic-crash–related fatality.
Needless to say, until improvements in science and technology provide conclusive evidence that the ICDs effectively and predictably provide life-saving therapy without actually testing them at the time of implantation, the dilemma of DFT testing will remain unsolved.
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References
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1. Strickberger SA, Klein GJ. Is defibrillation testing required for defibrillator implantation? J Am Coll Cardiol 2004;44:88-91.[Abstract/Free Full Text]
2. Swerdlow CD. Reappraisal of implant testing of implantable cardioverter-defibrillators J Am Coll Cardiol 2004;44:92-94.[Free Full Text]
3. Cummings P, McKnight B, Rivara FP, Grossman DC. Association of driver air bags with driver fatality: a matched cohort study BMJ 2002;324:1119-1122.[Abstract/Free Full Text]
4. Wallis LA, Greaves I. Injuries associated with airbag deployment Emerg Med J 2002;19:490-493.[Abstract/Free Full Text]
Related Article
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- Charles Swerdlow
J. Am. Coll. Cardiol. 2005 45: 468.
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