Final answer:
Immediate treatment for unstable SVT involves electrical cardioversion to restore a normal heart rhythm.
Step-by-step explanation:
If the client is unstable and experiencing supraventricular tachycardia (SVT), immediate treatment is necessary to stabilize their condition. The first-line treatment for unstable SVT is electrical cardioversion. This procedure involves delivering a controlled electric shock to the heart to restore a normal rhythm. Additionally, medication may be used to manage SVT, such as antiarrhythmic medications or beta-blockers.