Related Experiment Videos
Effect of ventricular shock strength on cardiac hemodynamics
1Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0022, USA.
Insights
Implantable defibrillator shocks exceeding 9 joules significantly reduce cardiac index by 10-15%. Lower energy shocks do not impact hemodynamics, suggesting lower energy defibrillation can avoid adverse effects.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Devices
Background:
- The hemodynamic impact of implantable defibrillator shocks is not well understood.
- Implantable defibrillators deliver electrical shocks to correct arrhythmias.
- Understanding shock effects is crucial for patient safety and device optimization.
Purpose of the Study:
- To investigate the adverse effects of implantable defibrillator shocks on cardiac hemodynamics.
- To test the hypothesis that ventricular defibrillator shocks negatively impact cardiac function.
Main Methods:
- Cardiac index was measured using transesophageal Doppler during defibrillator implantation in 17 patients.
- Measurements were taken before and at multiple time points after shocks of varying energy levels (1-34 J).
- Shocks were delivered during both defibrillation energy testing and baseline rhythm.
Main Results:
- High-energy shocks (27-34 J, 15 J, 10 J) significantly reduced cardiac index by 10-15%.
- The reduction in cardiac index persisted for up to 4 minutes and was dose-dependent.
- Low-energy shocks (1 J) did not significantly affect cardiac index.
Conclusions:
- Defibrillator shocks greater than 9 J adversely affect cardiac hemodynamics, reducing cardiac index.
- The magnitude and duration of hemodynamic compromise correlate with shock energy.
- Utilizing lower-energy defibrillation may mitigate detrimental hemodynamic effects.
Introduction:
The effect of implantable defibrillator shocks on cardiac hemodynamics is poorly understood. The purpose of this study was to test the hypothesis that ventricular defibrillator shocks adversely effect cardiac hemodynamics.
Methods And Results:
The cardiac index was determined by calculating the mitral valve inflow with transesophogeal Doppler during nonthoracotomy defibrillator implantation in 17 patients. The cardiac index was determined before, and immediately, 1 minute, 2 minutes, and 4 minutes after shocks were delivered during defibrillation energy requirement testing with 27- to 34-, 15-, 10-, 5-, 3-, or 1-J shocks. The cardiac index was also measured at the same time points after 27- to 34-, and 1-J shocks delivered during the baseline rhythm. The cardiac index decreased from 2.30 +/- 0.40 L/min per m2 before a 27- to 34-J shock during defibrillation energy requirement testing to 2.14 +/- 0.45 L/min per m2 immediately afterwards (P = 0.001). This effect persisted for > 4 minutes. An adverse hemodynamic effect of similar magnitude occurred after 15 J (P = 0.003) and 10-J shocks (P = 0.01), but dissipated after 4 minutes and within 2 minutes, respectively. There was a significant correlation between shock strength and the percent change in cardiac index (r = 0.3, P = 0.03). The cardiac index decreased 14% after a 27- to 34-J shock during the baseline rhythm (P < 0.0001). This effect persisted for < 4 minutes. A 1-J shock during the baseline rhythm did not effect the cardiac index.
Conclusion:
Defibrillator shocks > 9 J delivered during the baseline rhythm or during defibrillation energy requirement testing result in a 10% to 15% reduction in cardiac index, whereas smaller energy shocks do not affect cardiac hemodynamics. The duration and extent of the adverse effect are proportional to the shock strength. Shock strength, and not ventricular fibrillation, appears to be most responsible for this effect. Therefore, the detrimental hemodynamic effects of high-energy shocks may be avoided when low-energy defibrillation is used.