Air entrapment during S-ICD generator replacement can cause transiently high shock impedance that resolves after allowing time for air absorption.
Pocket air entrapment may transiently raise S-ICD impedance; this case leaves open optimal timing for defibrillation testing.
A 68-year-old lady with a subcutaneous implantable cardioverter-defibrillator (S-ICD) (Boston Scientific, MA, USA) for primary prevention underwent a pulse-generator substitution 4 years after implantation following manufacturer guidance. Sudden battery depletion had been detected on a routine pacing check; the battery longevity plummeted from 65% to 6% over a 6 months period. The generator replacement was unremarkable. To dispel air from the pocket before closure, saline irrigation was performed with tissue massage. Despite this, the shock impedance was unsatisfactorily high (135 Ω), and air entrapment in the pocket was confirmed on a chest radiograph (Figure). Having allowed air absorption, a repeat test was performed after 1 week: ventricular fibrillation was appropriately sensed and defibrillated (40 J) to sinus rhythm; shock impedance was now acceptable (98 Ω). Pocket air entrapment can occur during generator substitution. Air insulation increases impedance which may impede therapy. All air must carefully be expelled—a...
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Akhtar et al. (2021) studied this question.
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