The Defibrillation Conundrum: New Insights into the Mechanisms of Shock-Related Myocardial Injury Sustained from a Life-Saving Therapy

Figures

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  Figure 1. Main implantable cardiac defibrillators (ICD) technologies on the market. The historical technique uses a subcutaneous or submuscular can and an intracardiac lead implanted in the right ventricle through supra-caval venous access (Left Panel). Extracardiac technologies use an axillary can and a defibrillation lead tunneled subcutaneously in a para-sternal position or directly under the sternum in a para-cardiac position (Right Panel). Shocks are delivered between the hot can and the defibrillation lead coil.

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  Figure 2. The vicious circle of ICD shocks. High-energy shocks induce myocardial injury, as shown by elevated troponin serum levels. They also induce myocardial stunning, and subsequent reduced left ventricular ejection fraction (LVEF) and cardiac output. They finally induce directly and through acute heart failure a major catecholamines release, with proarrhythmic effects, which increases the risk of arrhythmia reinduction and ICD shocks.

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  Figure 3. Mechanisms of shock-related myocardial injury identified through a new proteomics approach [94]. Direct current induces electroporation of cardiolemma and direct cellular damages, but also promote regulated cell death, metabolic remodeling, oxidative stress, and calcium dysregulation. Proinflammatory and profibrotic pathways have also been identified.