In silico modeling of cardiac defibrillation with novel deep septal ICD leads

Abstract Background Recent studies have demonstrated that implantable cardioverter defibrillator (ICD) leads placed higher and deeper into the right ventricular (RV) septum, compared to traditional RV apical placement, were able to achieve conduction system pacing (CSP). A higher and deeper septal position may impact defibrillation thresholds (DFT) compared to the traditional ICD lead implant position. Purpose To compare DFTs associated with ICD leads implanted within the deep septum (CSP group) vs. an apical position (traditional). Methods In silico torso/heart models were generated from 5 human subjects (Figure). A commercially available ICD lead and a prototype 7Fr lead with a 5cm defibrillation coil were modeled in software, for apical and CSP positions, respectively, with a perpendicular insertion angle and nominal lead slack in the RV. For each torso model, a stable lead pathway was generated following simulated dynamic cardiac motion, for multiple positions: apical (control), deep high (1.5cm from tricuspid valve), deep mid (≈3.5cm from tricuspid valve), and deep low (midpoint of mid and apical) septal. The shock vector was between RV coil and ICD can placed at the 2nd rib. DFT energy was recorded at >5V/cm in 95% of ventricular tissue. Results are reported as median (range). Results The 5 torso models demonstrated a median left ventricular volume of 200cm³ (163 to 266cm³), 66Ω (56 to 77Ω) shock vector impedance, and 12cm (10 to 13cm) coil-to-can distance. For the apical position, the DFT was 18.4J (6.9 to 28.9J, n=5). As compared to apical, the CSP-positioned DFTs overall increased 1.4J (-0.6 to 4.4J, n=5), across all subjects. DFTs for deep high and mid septal nominally increased by 1.1J (-2.4 to 4.4J, n=5) and 1.8J (0.2 to 2.2J, n=3), respectively. The DFT for deep low septal slightly decreased by 0.3J (0.1 to 0.6J, n=2). All DFTs were substantially below defibrillation energies current ICDs offer. Conclusion Based on human torso models, ICD leads implanted in CSP positions resulted in a slight increase in DFTs compared to RV apical placement. With the maximum energies current ICDs offer, the slight DFT increase is not expected to substantially affect defibrillation efficacy. Larger clinical studies are needed to replicate these findings.In silico defibrillation modeling