Final answer:
The next appropriate intervention for the woman with light-headedness and palpitations is to administer a beta-blocker medication to control her tachycardia and relieve her symptoms.
Step-by-step explanation:
The next appropriate intervention for the 45-year-old woman with light-headedness and palpitations is to administer a beta-blocker medication to help control her tachycardia and relieve her symptoms. Beta-blockers are recommended as first-line treatment for tachycardia, and they work by blocking the effects of adrenaline on the heart, thereby reducing the heart rate. This intervention is important because persistent tachycardia can lead to complications such as heart failure or stroke.