CURRENT-BASED TRANSTHORACIC DEFIBRILLATION

This study examines in a prospective, multicenter trial the feasibilit y and advantage of current-based, transthoracic defibrillation. Curren t-based, damped, sinusoidal waveform shocks of 18, 25, 30, 35, or 40 a mperes (A) were administered beginning with 25 A for polymorphic ventr icular tachycardia (VT) and ventricular fibrillation (VF) or 18 A for monomorphic VT; success rates were compared with those of energy-based shocks beginning at 200 J for VF/polymorphic VT and 100 J for VT. The current-based shocks were delivered from custom-modified defibrillato rs that determined impedance in advance of any shock using a ''test-pu lse'' technique; the capacitor then charged to the exact energy necess ary to deliver the operator-selected current against the impedance det ermined by the defibrillator. Three hundred sixty-two patients receive d >1 shock for VF, polymorphic VT, or monomorphic VT: 569 current- bas ed shocks and 420 energy-based shocks. Current-based shocks of 35/40 A achieved success rates of up to 74% for VF/polymorphic VT; 30 A shock s terminated 88% of monomorphic VT episodes. Energy-based shocks of 30 0 J terminated 72% of VF/polymorphic VT; 200-J shocks terminated 89% o f monomorphic VT. We could not demonstrate a significant increase in t he success rate of current-based shocks over energy-based shocks for p atients with high transthoracic impedance; this may be due to inadequa te sample size. Thus, current-based defibrillation is clinically feasi ble and effective. A larger study will be needed to test whether curre nt-based defibrillation is superior to energy-based defibrillation. (C ) 1996 by Excerpta Medica, Inc.