Final answer:
The most appropriate intervention for a rapidly deteriorating patient with a persistent tachyarrhythmia shown on lead II ECG is urgent treatment with a controlled electric shock in the form of cardioversion or defibrillation.
Step-by-step explanation:
The most appropriate intervention for a rapidly deteriorating patient with a persistent tachyarrhythmia shown on lead II ECG would be urgent treatment with a controlled electric shock in the form of cardioversion or defibrillation. This involves delivering a large charge in a short burst to the patient's chest to terminate the arrhythmia and allow the heart to resume its normal rhythm. This can be done using a portable electronic device known as an automated external defibrillator (AED).