Evaluation of shock waveform configuration on the defibrillation capacity of implantable cardioverter defibrillators in dogs.

Implantable cardioverter defibrillators (ICD) are programmed to detect ventricular arrhythmias and terminate them by delivering an electrical shock. A defibrillation threshold (DFT) at least 10 J below the maximum device output is recommended for successful therapy. Shock waveform configuration is a programmable parameter used to achieve a low DFT. It is hypothesized that a fixed-pulse configuration results in lower defibrillation energy requirements than a fixed-tilt configuration. 10 mongrel dogs. ICD generator and transvenous lead were surgically implanted. Defibrillation threshold was determined using a protocol guided by the upper limit of vulnerability. Fixed-pulse and fixed-tilt (50%/50%) waveform configurations were tested in a random order. Plasma cardiac troponin I (cTnI) was measured for signs of myocardial injury. The experiment was completed in 9 dogs. Overall mean DFT value was 424 ± 88 V (9.2 ± 3.9 J). Mean differences among voltage, energy and impedance at the DFT for fixed-pulse (422 ± 97 V, 9.1 ± 4.2 J, 62.6 ± 13.8 Ω) and fixed-tilt (426 ± 83 V, 9.3 ± 3.8 J, 62.8 ± 18.5 Ω) configurations were not statistically significant (All P > 0.21). Cardiac TnI concentration changed from 0.03 ng/mL (95% CI: 0.02-0.04) at baseline to 0.11 ng/mL (95 CI: 0.08-0.16) after DFT was obtained with the first waveform configuration and 0.19 ng/mL (95% CI: 0.13-0.28) at the end of the study period. There were no significant changes in heart rate, end-tidal CO2 and blood pressure over time (all P > 0.09). The tested ICD device and lead placement reliably produced acceptable DFT values, based on a 10-J safety margin below the maximum device output. A benefit of fixed-pulse configuration could not be demonstrated over the standard fixed-tilt waveform. Signs of acute myocardial damage from repeated high-voltage shocks and episodes of ventricular fibrillation seemed of limited clinical significance. Copyright © 2012 Elsevier B.V. All rights reserved.

Citation

Romain Pariaut, Carley Saelinger, Jorge Vila, William Deforge, Patricia Queiroz-Williams, Hugues Beaufrère, Michael Zimmerman, Katrin Saile, Caryn A Reynolds. Evaluation of shock waveform configuration on the defibrillation capacity of implantable cardioverter defibrillators in dogs. Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology. 2012 Sep;14(3):389-98

Mesh Tags

Substances

PMID: 22819488

search → result