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?

A. Atrial fibrillation (AF) is characterized by irregular, often rapid atrial contractions that lead to ineffective ventricular filling. This can result in a pulse deficit, where the apical pulse rate is higher than the radial pulse rate because some ventricular contractions do not produce a palpable pulse. Assessing for a pulse deficit is a key clinical indicator of AF. B. While pericarditis or associated heart failure may cause pulmonary congestion, differences in lung sounds do not specifically indicate atrial fibrillation. They are more relevant for pulmonary assessment rather than detecting arrhythmias. C. Discrepancies in blood pressure between arms may suggest vascular obstruction or coarctation of the aorta, but it is not indicative of atrial fibrillation. D. Variations between oral and axillary temperatures reflect measurement differences or thermoregulation, not cardiac rhythm disturbances. They do not indicate atrial fibrillation.