Predictors of a high defibrillation threshold test during routine ICD implantation

Patients with a high defibrillation threshold: Approaches to management

Implantable cardioverter-defibrillators (ICDs) have revolutionized the prognosis for patients at elevated risk of ventricular tachyarrhythmias. For safety, defibrillation should be effective with a minimum of 10 J below the device's maximum energy. While modern ICDs rarely deliver ineffective shocks in primary prevention, the surge in managing severe heart failure patients has led to an increased number of patients with high defibrillation thresholds (DFTs). This article elucidates the potential causes of high DFT, including clinical factors, lead and device placement, the presence of a Left Ventricular Assist Device (LVAD), prolonged ventricular arrhythmias, shock vectors, waveform tilt, medications, and manufacturer-specific options. We also detail management strategies, highlighting alternative shock coil placements, practical recommendations, and case studies from our institution. Our management algorithm suggests addressing preventable causes, re-evaluating coil positions, considering non-invasive system modifications, upgrading to a higher-capacity device, and adding extra coil(s).

High defibrillation threshold with right-sided ICD implantation was resolved by a dual coil lead via persistent left superior vena cava

Persistent left superior vena cava (PLSVC) can be problematic when device implantation is scheduled from the left side because of the technical difficulty in delivering leads. Right-sided implantation is an alternative method, but there is a risk of a high defibrillation threshold (DFT). Transvenous implantation of an implantable cardioverter defibrillator (ICD) was scheduled for a 54-year-old man with idiopathic dilated cardiomyopathy and monomorphic non-sustained ventricular tachycardia, but computed tomography revealed the presence of a PLSVC. Right-sided ICD implantation was performed first; however, an ICD shock at 35 J failed to terminate the induced ventricular fibrillation (VF). Re-implantation via the PLSVC by a left subclavian approach with a dual coil lead was performed next. The dual coil right ventricular lead was successfully implanted via the PLSVC, and the induced VF was terminated by a single shock at 25 J. In the present case, the proximal coil was located in the coronary sinus (CS) and it enabled an antero-posterior defibrillation vector across the left ventricle. In addition to the re-location of the ICD generator from the right side to the left side, the new positioning of the proximal coil inside the CS is likely to have contributed to the great improvement of the DFT. .

Important Parameters for Implantable Cardioverter Defibrillator Selection

The efficacy of implantable cardioverter defibrillators in reducing the risk of sudden cardiac death has been well established by several clinical trials. Several factors relating to device characteristics, patient attributes, and comorbidities should be considered when selecting the appropriate implantable cardioverter defibrillators for each patient. This review examines some of these issues.