What is the most appropriate first step in managing a patient with angina and ST changes on an ECG?

In the context of managing a patient with angina and ST changes on an ECG, the administration of aspirin is a critical initial step. Aspirin plays a vital role in the immediate management of suspected acute coronary syndrome, including angina. Its antiplatelet properties help prevent the progression of the clotting process that may be occurring in coronary arteries. By inhibiting platelet aggregation, aspirin can reduce the risk of thrombus formation, which can exacerbate ischemia in the heart muscle.

While other interventions, such as nitroglycerin, can also be beneficial—particularly for relieving angina—they do not address the underlying thrombotic process as directly as aspirin does. Additionally, placing the patient on oxygen may provide symptomatic relief by improving oxygenation but does not treat the potential underlying problem of platelet aggregation. Performing CPR is reserved for patients who exhibit cardiac arrest and is not suitable here since the patient is experiencing angina with ST changes, not a loss of circulatory function.

Thus, initiating treatment with aspirin is the most appropriate first step because it effectively targets the underlying pathology associated with acute coronary syndromes and does so quickly in a pre-hospital or emergency setting.