Diathermy-induced ventricular fibrillation with Riata high-voltage lead insulation failure

Abstract

We report a case of diathermy-induced ventricular fibrillation as a result of insulation failure in high-voltage lead at the level of thepectoral muscles.A 76-year-old man presented to a small peripheral hospital after a series of six shocks in quick succession from his implanted biven-tricular defibrillator (St Jude Medical Promote Accel RF device; right atrial, right ventricular, and left ventricular leads were SJM1688T,SJM1570 Riata, and SJM1258T, respectively). A short period of palpitations and pre-syncope preceded the shocks and symptoms per-sisted despite the shocks. Initial 12-lead electrocardiogram revealed ventricular tachycardia at 180 b.p.m. A retrieval team deliveredone 200 J shock with successful return to sinus rhythm. The man was then transferred to our institution.His last implantable cardioverter defibrillator follow-up 2 months prior to the present episode was normal.Interrogation of the device revealed that the device had been reset. Neither the episodes nor the therapies delivered were access-ible. The data could not be retrieved despite interrogation by the company’s technical services division. The parameters differed fromthose 2 months earlier (high-voltage lead impedance 14 vs. 42 V, thresholds for right ventricular, left ventricular, and right atrial leadswere 2.75 vs. 0.75 V, 4.75 vs. 1.5 V, and 3.25 vs. 1.25 V, respectively). The therapies were disabled.The patient was taken to the cardiac catheterization lab for a replacement.During dissection to free the leads, ventricular fibrillation was noted immediately following diathermy application. Three external200 J shocks were required to return to sinus rhythm. The diathermy knife was ,1 cm from the leads at the time of ventricularfibrillation onset. It is worth noting that diathermy to subcutaneous tissue earlier on during the procedure did not have anyadverse outcome. Further dissection without diathermy revealed a clear insulation failure of the high-voltage lead (Figure 1).The defective lead was cut and capped. A new high-voltage lead (Medtronic Sprint Secure 6935) and a new device (MedtronicConcerto II) were implanted with excellent parameters on all three leads.We postulate the following sequence of events in the absence of recorded data. Because of the insulation defect in the high-voltagelead, there was no effective current delivered to the heart during the initial series of six shocks. Instead, all or most of the current‘short circuited’ between the lead defect and the device. The external shock not only terminated the ventricular tachycardia, butalso reset the device, quite probably by current entering through the exposed lead and travelling retrograde to the device. Diathermyclose to the exposed lead carried alternating current to the left ventricle inducing ventricular fibrillation.The company has issued a recall for the Riata and Riata ST silicone endocardial leads due to insulation failure.