Effect of duration of ventricular fibrillation on defibrillation efficacy in humans.

Abstract

The currently available automatic implantable cardioverter-defibrillator has proven highly successful for termination of ventricular tachycardia and fibrillation. Newer devices, however, permit lower energy shocks to be delivered initially and longer episodes of arrhythmia to occur before shocks are delivered. These changes may result in longer durations of arrhythmia before successful termination. Little is known about the effects of the duration of ventricular fibrillation on the efficacy of defibrillating shocks. In this study, we examined the efficacy of defibrillating shocks in 22 patients undergoing automatic implantable cardioverterdefibrillator implantation or generator change. Defibrillating shocks ranging from 300 to 600 V (5.9-24.2 J) were delivered in matched pairs after 5 and 15 seconds of ventricular fibrillation. For the 300-V shocks (5.9 J), defibrillation was accomplished in 82% of patients when the shocks were given after 5 seconds of ventricular fibrillation and in only 45% of patients when the shocks were delivered after 15 seconds (p<0.01). At higher energies, there was no difference in the efficacy of defibrillation shocks delivered after 5 compared with 15 seconds of ventricular fibrillation. The postshock aortic, systolic, and diastolic blood pressures were significantly lower when the shocks were given after 15 seconds of ventricular fibrillation than after only 5 seconds. We conclude that the duration of ventricular fibrillation affects defibrillation efficacy especially at energies that are relatively low compared with maximal device outputs and that longer episodes of ventricular fibrillation cause more postshock hemodynamic depression. These observations have implications for defibrillation threshold testing at the time of device implantation and for the design and programming of future automatic implantable antitachycardia devices. (Circulation 1990;81:1477-

Clinical impact of defibrillation testing at the time of implantable cardioverter-defibrillator insertion

“…Similarly, a significant proportion (80-87%) of VT/fast VT episodes were successfully ATP-terminated without shock delivery, regardless of whether DT was performed. This is consistent with previous studies showing that dedicated ATP programming reduce the need for shocks to terminate VT/VF in a substantial number of patients [7,17,23]. In addition, newer devices are able to deliver ATP during energy charge when treating a VF episode, in an attempt to terminate a fast VT detected in the VF zone [24,25].…”

“…Moreover, this is the first study to provide detailed analyses of the outcome of ICD therapies, both ATP and shocks, showing a similar first shock efficacy in patients following failed ATP therapy in patients with and without DT at implant. Since ATP therapy failure delays time to shock and prolongs VF duration, a lower shock efficacy could have been expected in this context [23,26]. It is reassuring to note that in our study, all VT/VF episodes following failed ATP were successfully converted when first shock was programmed at maximum energy, regardless DT was performed or not.…”

“…In addition, newer devices are able to deliver ATP during energy charge when treating a VF episode, in an attempt to terminate a fast VT detected in the VF zone [24,25]. Interestingly, we observed no first shock failures following ineffective ATP therapies, both in DT+ and DTpatients, since all first shocks were programmed at maximum energy [23].…”

“…Patients in the DT+ group were followed for a longer period than DT-patients (32 vs. 15 [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] months; p < 0.001). After adjusting the event rate by the follow-up duration, there was no significant difference in the death rate per observation year (DT+: 0.04 vs. DT-: 0.04; p = 0.91) nor in the rate of patients with ventricular arrhythmic events per observation year (DT+: 0.10 vs. DT-: 0.12; p = 0.46) ( Table 2).…”

Implantierbarer Kardioverter-/Defibrillator: Langzeitstabilität der Defibrillationsschwelle mit einer unipolaren Elektrodenkonfiguration („Active-Can“)

“…Die Defibrillationsschwelle ist von vielen Faktoren abhän-gig, u. a. von der Wahl der Schockform (13, 30), von der Größe und Form der Elektroden (11), der Konfiguration der Elektroden (13,25), von der im Defibrillationsfeld gelegenen Muskelmasse (5), von der Dauer der tachykarden Rhythmusstörung (32) und von einer gleichzeitigen antiarrhythmischen Medikation (7,24). Je kürzer die Dauer der Tachyarrhythmie, desto niedriger fällt die Defibrillationsschwelle aus (32). Somit kann ein Anstieg oder ein Abfall der notwendigen Defibrillationsenergie von diesen Faktoren abhängig sein und in Einzelfällen auch mittels dieser erklärt werden.…”