Key result
Subcutaneous ICD shocks expose 0 cc of ventricular myocardium to high-voltage gradients versus transvenous ICDs.
Why the study?
Transvenous ICD shocks are associated with cardiac biomarker elevations and potential myocardial damage from excessive voltage gradients, but comparative data with subcutaneous ICDs are limited.
Do subcutaneous defibrillator shocks produce lower myocardial voltage gradients compared to transvenous defibrillator shocks?
Do subcutaneous defibrillator shocks produce lower myocardial voltage gradients compared to transvenous defibrillator shocks?
Computational modeling suggests that subcutaneous ICD shocks produce more uniform myocardial voltage gradients with less exposure to potentially damaging electrical fields compared to transvenous ICDs.
Answers are grounded in this paper and cite their sources.
May limit high-gradient myocardial exposure with S-ICD; leaves open translation to reduced injury in humans.
INTRODUCTION: Transvenous implantable cardioverter-defibrillator (ICD) shocks have been associated with cardiac biomarker elevations and are thought in some cases to contribute to adverse clinical outcomes and mortality, possibly from myocardium exposed to excessive shock voltage gradients. Currently, there are only limited data for comparison with subcutaneous ICDs. We sought to compare ventricular myocardium voltage gradients resulting from transvenous (TV) and subcutaneous defibrillator (S-ICD) shocks to assess their risk of myocardial damage. METHODS: A finite element model was derived from thoracic magnetic resonance imaging (MRI). Voltage gradients were modeled for an S-ICD with a left-sided parasternal coil and a left-sided TV-ICD with a mid-cavity, a septal right ventricle (RV) coil, or a dual coil lead (TV mid, TV septal, TV septal + superior vena cava [SVC]). High gradients were defined as > 100 V/cm. RESULTS: The volumes of ventricular myocardium with high gradients > 100 V/cm were 0.02, 2.4, 7.7, and 0 cc for TV mid, TV septal, TV septal + SVC, and S-ICD, respectively. CONCLUSION: Our models suggest that S-ICD shocks produce more uniform gradients in the myocardium, with less exposure to potentially damaging electrical fields, compared to TV-ICDs. Dual coil TV leads yield higher gradients, as does closer proximity of the shock coil to the myocardium.
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Belalcazar et al. (2023) studied Implantable cardioverter-defibrillator (ICD) shocks. Subcutaneous ICD (S-ICD) vs. Transvenous ICD (TV-ICD) was evaluated on Volume of ventricular myocardium with high voltage gradients (> 100 V/cm). Subcutaneous ICD shocks produced 0 cc of ventricular myocardium with high voltage gradients (>100 V/cm), compared to 0.02 to 7.7 cc for transvenous ICD configurations.
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