A nurse is caring for a client who has pericarditis and reports feeling a new onset of palpitations and shortness of breath. Which of the following assessments should indicate to the nurse that the client may have developed atrial fibrillation?

Atrial fibrillation is a supraventricular tachyarrhythmia characterized by disorganized atrial electrical activity and ineffective atrial contraction. The resulting ventricular response is typically irregularly irregular, leading to hemodynamic instability and a significant reduction in cardiac output due to the loss of the atrial kick. A. Differences in upper and lower lung sounds usually indicate localized pulmonary pathology such as pneumonia, pleural effusion, or atelectasis. While heart failure resulting from chronic arrhythmias can cause bibasilar crackles, this assessment is not a specific or direct diagnostic indicator for the presence of atrial fibrillation. B. Obtaining different blood pressure readings in the left and right arms is a clinical finding often associated with aortic dissection or subclavian steal syndrome. It indicates a mechanical obstruction or structural abnormality in the large arteries rather than an electrical conduction disturbance within the atria of the heart. C. The statement that there is no erratic nature of atrial contractions is factually incorrect regarding the pathophysiology of atrial fibrillation. In this arrhythmia, the atria quiver chaotically at rates of 300 to 600 beats per minute, which is the definition of erratic and disorganized muscular activity. D. A pulse deficit occurs when the apical heart rate exceeds the radial pulse rate, indicating that some ventricular contractions are too weak to produce a palpable peripheral pulse. This is a classic finding in atrial fibrillation because the shortened diastolic filling time prevents adequate stroke volume during many beats.