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Replacement Versus Intensified Follow-Up in Patients With ICDs Affected By a Potentially Deleterious Internal Error: Presented at ESC

By Chris Berrie

VIENNA, AUSTRIA -- September 6, 2007 -- The replacement of an implantable cardiovascular defibrillator (ICD) arising from manufacturer-informed internal errors that could result in loss of function should be considered with caution due to potential for a significant rate of adverse events associated with replacement, researchers report.

The findings were presented here on September 3rd at the European Society of Cardiology (ESC) Congress by coinvestigator Torsen Becker, MD, Resident Cardiologist, Heartcentre, Ludwigshafen, Germany.

In 2005 information was released by the manufacturer of distinct ICD models stating that unpredictable battery depletion could lead to complete loss of function. With nearly 90,000 such devices implanted worldwide, 73 (0.08%) had been confirmed to have failed by January 2007, with projected failure rates predicted to reach 1.5%.

Dr. Becker said, "On the one hand, you have the criteria of how big the danger is for the patient if the generator doesn't work any more, and on the other hand, you have the problem that by replacing the generator you may have serious complications." Therefore, the purpose of this study was to determine the decision algorithms of whether to replace these potentially defective ICD generators or to perform only intensive follow-up examinations.

Initially, the researchers identified all 49 patients involved and the criteria in favour of device replacement were defined: ICD for secondary prophylaxis; former adequate episodes; pacemaker dependency; expectation of poor compliance with intensified follow-up; wish of the patient; and battery depletion levels.

One patient was lost to follow-up and three patients died. Of the remaining 45 patients, two of these showed lead defects, a mandatory indication for surgery; of the remaining 43 patients, 21 (86% male) were scheduled for ICD replacement surgery, and 23 (64% male) for intensified follow-up.

Baseline (pre-follow-up) clinical characteristics across these replacement/follow-up groups were similar for structural heart disease (100% vs 95%), left ventricular ejection fraction 40% or less (86% vs 77%), antithrombotic therapy (76% vs 86%), cardiac resynchronisation therapy-ICD (52% vs 32%), and ICDs implanted prior to affected ICD (29% vs 18%).

However, the ICD replacement group showed significantly greater secondary prophylaxis (95% vs 50%; P <.005) and pacemaker dependency (24% vs 0.0%; P <.05), and a tendency towards adequate episodes (38% vs 18%; P =.15), although they were also older (67 vs 53 years; P <.05) and showed greater renal impairment (62% vs 23%; P <.05).

Of note, the intensified follow-up group included 11 patients (50%) who refused advice for ICD replacement, and one patient requested replacement although it was not advised.

The ICD replacement was achieved with a mean duration of surgery of 33 minutes, and a mean of 8 days of hospitalisation. In comparison, patient compliance with intensified follow-up saw 36% missing monthly visits and 27% without daily magnet control; however, none opted for crossover to ICD replacement.

Adverse effects associated with ICD replacement during this follow-up period were procedure related: life-threatening effects in 2 patients (periprocedural disabling stroke and infection of ICD pocket/ system; 10%); and non-life-threatening effects in two patients (significant pocket haematoma, 10%). Other adverse effects during follow-up were two deaths (10%) due to terminal heart failure, and three patients (14%) with a defect of the high-voltage lead, an exit block of the RV lead, and a repetitive electrical storm with transient ischaemic attack.

For the intense follow-up group, none experienced rapid battery depletion during follow-up, but three died of terminal heart failure (14%), and three others experienced incessant catheter ablation of ventricular tachycardia, acute coronary syndrome, and heart transplantation.

On the basis of these outcomes, and while noting that the replacement group included a greater frequency of ICD for secondary prophylaxis and older and sicker patients, Dr. Becker said that the ICD replacement due to this internal error led to a significant rate of adverse effects in these patients.

"After our experiences, we have a much higher threshold to replace the ICD generator," he added. Therefore, where there is a low likelihood of loss of function of an ICD, its replacement should be considered with caution, even in patients who are at high risk of arrhythmia.

[Presentation title: ICD Replacement Versus Intensified Follow-Up in Patients With ICDs Affected By a Potentially Deleterious Internal Error. Abstract P1841]

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