A nurse is teaching the partner of a client who had an acute myocardial infarction (MI) about the reason blood was drawn from the client. Which of the following statements should the nurse make regarding cardiac enzyme studies?

The P wave is the first wave on the ECG strip and represents the electrical activity of the atria. It reflects the depolarization of the atrial myocardium, which is the process of changing the electrical charge of the cardiac cells from negative to positive, triggering a contraction. The P wave precedes the QRS complex, which represents ventricular depolarization, and the T wave, which represents ventricular repolarization.

The other options are not correct because:

a. Slow repolarization of ventricular Purkinje fibers. This statement is incorrect because it describes the U wave, which is a small and sometimes invisible wave that follows the T wave on the ECG strip. It reflects the repolarization of the ventricular Purkinje fibers, which are specialized cardiac cells that conduct electrical impulses to the ventricles. The U wave is more prominent in conditions that cause hypokalemia, such as diuretic use or vomiting.

c. Early ventricular repolarization. This statement is incorrect because it describes the ST segment, which is the flat line between the QRS complex and the T wave on the ECG strip. It reflects the early phase of ventricular repolarization, which is the process of restoring the electrical charge of the cardiac cells to negative after a contraction. The ST segment can be elevated or depressed in conditions that cause myocardial ischemia or injury, such as angina or myocardial infarction.

d. Ventricular depolarization. This statement is incorrect because it describes the QRS complex, which is the largest and most visible wave on the ECG strip. It reflects the depolarization of the ventricular myocardium, which triggers a ventricular contraction. The QRS complex follows the P wave and precedes the T wave on the ECG strip.

Planning to slow down if tired the day after exercising is a statement that indicates the client understands the importance of pacing activities and avoiding overexertion, which can worsen heart failure symptoms.

a. "I should use naproxen to manage discomfort." is not correct, as naproxen is a nonsteroidal anti-inflammatory drug (NSAID) that can cause fluid retention, increase blood pressure, and worsen heart failure. The client should avoid NSAIDs and use other analgesics, such as acetaminophen, unless contraindicated.

c. "I will read food labels and limit my sodium to 4 grams per day." is not appropriate, as 4 grams of sodium per day is too high for a client who has congestive heart failure. The client should limit sodium intake to 2 grams or less per day, as sodium can cause fluid retention and increase the workload of the heart.

d. "I will take my diuretic before sleep and drink fluids during the day." is not advisable, as taking a diuretic before sleep can cause nocturia and disrupt the sleep cycle, which can affect the quality of life and cardiac function. The