What laboratory test should the nurse prioritize for diagnosing a myocardial infarction?

• A. Obtain a serum creatinine kinase (CK) level.
• B. Obtain a 12-lead ECG.
• C. Prepare for cardiac catherization.
• D. Initiate thrombolytic therapy.

Answer: (B)

Obtaining a 12-lead ECG is crucial for diagnosing a myocardial infarction (MI) because it provides immediate information about the heart's electrical activity and can identify characteristic patterns associated with an MI, such as ST-segment elevation or depression. This rapid assessment allows healthcare providers to make timely decisions regarding further interventions.

In the context of diagnosing an MI, the ECG is a critical first step because it not only helps confirm the diagnosis but also guides subsequent management, such as the need for thrombolysis or the urgency of catheterization. While serum creatinine kinase levels can indicate muscle damage, including cardiac muscle, they are not as immediate or specific as the 12-lead ECG for diagnosing an active myocardial infarction. Cardiac catheterization and thrombolytic therapy are usually considered after the diagnosis has been confirmed and are not diagnostic tests in themselves. Thus, the ECG remains the prioritized test for quickly identifying an MI and assessing the severity of the condition.