Leakage of energy to the body surface during defibrillation shock by an implantable cardioverter-defibrillator (TCD) system - Experimental evaluationduring defibrillation shocks through the right ventricular lead and the subcutaneous active-can in canines

The leakage of electrical current to the body surface during defibrillation shock delivery by an implantable cardioverter-defibrillator (ICD) device ( the Medtronic Jewel Plus PCD system) was evaluated in 5 dogs. The defibrill ation shocks were delivered between the active-can implanted in the left su bclavicular region and the endocardial lead placed in the right ventricle a t the energy levels of 1, 2, 8, 12, 24 and 34J. During each delivery, the e lectrical current leakage from the body surface was measured by electrodes connected to a circuit at 4 recording positions: (A) parallel-subcutaneous (the electrodes were fixed in the subcutaneous tissue of the left shoulder and the right lower chest, and the direction of the electrode vector was pa rallel to the direction of the defibrillation energy flow); (B) cross-subcu taneous (the electrodes were fixed in the subcutaneous tissue of the right shoulder and the left lower chest, and the Vector of the electrodes was rou ghly perpendicular to the direction of the energy how); (C) parallel-surfac e (the electrodes were fixed with ECG paste on the shaved skin surface at t he left shoulder and the right lower chest); and (D) surface grounded (the electrodes were fixed on the shaved skin surface at the left shoulder and t he left foot, which was grounded). The circuit resistance was set at a vari able level (100-5,000 Ohm) in accordance with the resistance measured throu gh each canine body. Leakage energies were measured in 750 defibrillation s hocks with each circuit resistance in 5 dogs. The leakage energy increased in accordance with the increase of the delivered energy and the decrease of the circuit resistance in all 4 recording positions. When the circuit resi stance was set at 1,000 Ohm, the leakage energy during shock delivery at 34 J was 32+/-17 mi at position A, 5+/-9 mJ at B, 10+/-9 mJ at C, and 4+/-3 mJ at D (p=0.042). The peak current was highest at position A and was 87+/-22 mA with a circuit resistance of 1,000 Ohm. The power of the leakage energy depended on the delivered energy and the impedance between the electrodes. The angle between the alignment of the recording electrodes and the direct ion of the energy flow was another important factor in determining the leak age energy. Although the peak current of the leakage energy reached the lev el of macro shock, the highest leakage energy from the body surface was con siderably less because of the shea duration of the shock delivery.