Serum cardiac markers are proteins released into the bloodstream from necrotic heart tissue after a myocardial infarction (MI). Troponin is a highly specific cardiac marker for the detection of MI. It has greater sensitivity and specificity for myocardial injury than creatine kinase (CK) MB. Serum levels of troponin increase 4-6 hours after the onset of MI, peak at 10-24 hours, and return to baseline after 10-14 days. A troponin value of 0.7 ng/mL (0.7 mcg/L) indicates cardiac muscle damage and should be the priority and immediate focus of the nurse. Normal values: troponin 1 <0.5 ng/mL (<0.5 mcg/L); troponin T <0.1 ng/mL (<0.1 mcg/L).

(Option 1) The glucose is elevated (normal random glucose 70-110 mg/dL [3.9-6.1 mmol/L]) but is not the priority in this situation. The nurse will need to assess whether the client has a history of diabetes and time of the last meal.

(Option 2) Normal hematocrit for a male is 39%-50% [0.39-0.50] and 35%-47% [0.35-0.47] for a female. The hematocrit value is not the priority.

(Option 3) The potassium is slightly below normal (3.5-5.0 mEq/L [3.5-5.0 mmol/L]). This should be the nurse's second priority. A low potassium level can precipitate dysrhythmias.

Educational objective: An elevated troponin value holds the highest priority for intervention when a client is experiencing chest pain. Positive troponin levels are indicative of myocardial injury and require immediate attention by the nurse. Normal values are <0.5 ng/mL (<0.5 mcg/L) for troponin I and <0.1 ng/mL (<0.1 mcg/L) for troponin T