Document Type

Conference Proceeding

Publication Date


Publication Title

J Am Coll Cardiol


Background: In patients with implantable cardioverter-defibrillators (ICD) and high defibrillation thresholds (DFT) who fail appropriate shocks, steps should be taken to lower DFT. However, options might be limited. Here, we present a case of a patient whose DFT was lowered using an intuitive method.

Case: A 64-year-old male with non-ischemic cardiomyopathy status post ICD implant presented to the ER with ICD shocks. Patient had prior history of ventricular tachycardia (VT) that resulted in multiple ICD shocks. He had VT storm on sotalol with acute renal failure. He had a VT ablation but continued to have VT afterwards while on amiodarone and mexiletine. The ICD was initially implanted in 2005 with a Medtronic 6949 Sprint Fidelis DF-1 lead in the right ventricular (RV) high septum. A Medtronic 6996 subcutaneous (SQ) coil was added in 2011 after some failed shocks. In 2013, a new Medtronic 6935 RV Quattro DF-1 ICD lead in the RV apex was added. A device upgrade to a dual chamber biventricular ICD was done due to being pacer-dependent and due to a secondary prevention indication for his ICD. His Fidelis lead was abandoned. In the ER, his device interrogation showed he failed his first shock at the maximum of 35 J. His following shock at the same output succeeded.

Decision-making: Options in this patient included adding a second coil (azygous or coronary sinus vein) or a second SQ, using a generator with a higher output, and/or reversing polarity. A venogram was done that showed extensive occlusion, likely to the azygous vein origin. A Medtronic Cobalt DTPB2D1 ICD 40 J generator was placed. We decided to use a Medtronic DF-1 6726 y-adapter to combine the RV coils of the Quattro and abandoned Fidelis leads. DFT testing was performed twice successfully at 15 J. Due to low RV impedance (24 Ω), we tested DFT twice more without the SQ coil successfully at 15 J (34 Ω). If that failed, we would have added a second SQ coil and merged it with the previous SQ coil. If that failed, extraction and reimplantation of coil in the coronary sinus vein would have been done.

Conclusion: Combining 2 RV coils from different locations is an effective way to significantly lower DFT, likely by lowering the shock impedance and increasing the shock tissue surface area.





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