Synchronised cardioversion - ECG timing (R wave, avoiding T wave)
Core concept
- Synchronised = the defibrillator delivers the shock on the R wave of the QRS
- Explicitly avoids the T wave = the vulnerable period of ventricular repolarisation
- A shock landing on the T wave -> R-on-T -> ventricular fibrillation
- The vulnerable period corresponds to the relative refractory period - some myocytes repolarised, some not -> maximal dispersion of refractoriness -> a stimulus can capture some fibres and not others -> re-entry and VF
- -> Synchronise for any organised rhythm with a QRS. Do not synchronise when there is nothing to synchronise to.
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