Prospective Randomized Comparison of 50%/50% Versus 65%/65% Tilt Biphasic Waveform on Defibrillation in Humans

Abstract

It is unknown if there is a single optimal biphasic waveform for defibrillation. Biphasic waveform tilt may be an important determinant of defibrillation efficacy. The purpose of this study was to compare acute defibrillation success with a three-electrode configuration in humans using 50%/50% versus 65%/65% tilt truncated exponential, biphasic waveforms delivered through a 110-microF capacitor. Acute DFTs for biphasic waveforms with 50%/50% versus 65%/65% tilt were measured in random order in 60 patients using a binary search method. The electrode configuration consisted of a RV coil as the cathode, and a SVC coil plus a pectoral active can emulator (CAN) as the anode. The waveforms were derived from an external voltage source with 110-microF capacitance, and the leading edge voltage of phase 2 was equal to the trailing edge voltage of phase 1. Stored energy DFT (9.2 +/- 5.7 [50%/50%] vs 10.8 +/- 6.4 [65%/65%] J, P = 0.007), current DFT (10.9 +/- 4.0 [50%/50%] vs 12.0 +/- 4.4 [65%/65%] A, P = 0.002) and voltage DFT (391 +/- 118 [50%/50%] vs 424 +/- 128 [65%/65%] V, P = 0.004) were significantly lower for the 50%/50% tilt waveform versus the 65%/65% tilt waveform using this three-electrode configuration and a 110-microF capacitor. For an RV(-)/SVC plus CAN(+) electrode configuration and a 110-microF capacitor, a 50%/50% tilt biphasic waveform results in a 15% reduction in energy DFT, 9% reduction in current DFT, and 8% reduction in voltage DFT versus a 65%/65% tilt biphasic waveform.

The Dilemma of ICD Implant Testing

“…For fixed‐tilt waveforms, duration depends on the waveform time constant. The performance of some fixed‐tilt waveforms can be improved either by different waveform truncation based either on tilt 129 or duration 130–132 . For commercial ICDs with fixed duration waveforms, initial recommended programming is based on an estimated cardiac membrane time constant of 3.5 ms 130–132 .…”

Implantable Intravascular Defibrillator: Evaluation of Defibrillation Waveforms with Inferior Vena Cava Electrode System

“…Those studies found that lower DFTs at lower tilts have smaller system time constants, and those not demonstrating an effect have had relatively higher time constant. Natale et al and Sweeney et al both reported lower DFTs when tilt was lowered to 50% from 65% utilizing a biphasic waveform with three‐electrode systems (110‐μF capacitor) 3,4 . These studies had system time constants less than 5 ms (4.8 and 4.1, respectively).…”

“…Multiple studies have examined options for alterations of biphasic waveforms for currently available cardioverter defibrillators 1–6 . Conventional implantable cardioverter defibrillators (ICDs) deliver a biphasic waveform which is truncated after the voltage has declined exponentially by 50–65% of the initial value 7 .…”

“…Multiple studies have examined options for alterations of biphasic waveforms for currently available cardioverter defibrillators. [1][2][3][4][5][6] Conventional implantable cardioverter defibrillators (ICDs) deliver a biphasic waveform which is truncated after the voltage has declined exponentially by 50-65% of the initial value. 7 The term "tilt" is used to describe this percentage decrease in voltage from the beginning of each phase (P1 and P2) of a truncated biphasic waveform.…”

Elevated Defibrillation Threshold Despite Programmable Tilt, Pulse Width, or Implant of Subcutaneous Coil: Role of Higher Energy Devices

“…The patient received propofol for anesthesia and a minimum interval of 5–6 minutes was used between each test. For the first attempt, the tilt of the defibrillating waveform was reprogrammed from 65% to 50%, 6 the shock failed, and the patient was externally defibrillated. Other attempts were made with and without the superior vena cava (SVC) coil, but a consistent DFT between 25 and 27 J (740 V) could not be obtained in order to achieve adequate safety margins (Table I).…”