Final answer:
The nurse should check the client's blood pressure manually first.
Step-by-step explanation:
The nurse should check the client's blood pressure manually first after hearing the sound. This is because a myocardial infarction, or heart attack, can cause changes in blood pressure. By checking the blood pressure manually, the nurse can assess if the client's blood pressure is within normal range or if further intervention is needed. It seems like you mentioned hearing a sound, but the options provided don't include information about the sound or the assessment findings. If you could provide more details or context about the sound or the specific findings during the cardiac assessment, I would be better able to assist you in selecting the most appropriate action.