Orthostatic increase in defibrillation threshold leading to defibrillation failure and prolonged cardiac arrest in a sitting position: Lessons from a patient’s near-fatal experience

Introduction It has previously been reported that patients with an implantable cardioverter-defibrillator (ICD) may have a slightly higher defibrillation threshold (DFT) in an upright position compared to a supine position. However, the significance of this and the potential impact on clinical practice remains unclear. We report a case of defibrillation failure caused by an increase in DFT in the upright position, leading to prolonged, near-fatal cardiac arrest in a patient who had previous ICD implantation including successful DFT testing in a supine position. ICD system revision with addition of an azygos vein coil successfully corrected this condition, as demonstrated by orthostatic DFT testing.