Final answer:
Non-shockable forms of cardiac arrest include asystole and pulseless electrical activity (PEA), which cannot be treated with defibrillation like ventricular fibrillation.
Step-by-step explanation:
In the context of cardiac arrest, there are two main types of heart rhythms that are considered non-shockable: asystole and pulseless electrical activity (PEA). Asystole is a flatline on the ECG, indicating no electrical activity and no heartbeat.
PEA is a condition where electrical activity is observed on the ECG, but it does not result in a pulse or effective cardiac output, hence the heart is not pumping blood effectively. These non-shockable rhythms cannot be treated with defibrillation, unlike ventricular fibrillation, which can potentially be terminated with an electric shock delivered by a defibrillator.
External Automated Defibrillators (EADs) are commonly available in public spaces to provide immediate treatment for ventricular fibrillation, allowing the heart to potentially return to a normal sinus rhythm.