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?

Rationale: A. Differences in upper and lower lung sounds are incorrect because lung auscultation findings are related to respiratory issues (e.g., fluid, consolidation, or obstruction), not directly to cardiac rhythm disturbances like atrial fibrillation (AF). B. Differences between oral and axillary temperatures are incorrect because temperature variations reflect measurement site differences, not cardiac arrhythmias. C. Different blood pressures in the upper limbs is incorrect because blood pressure differences between arms may indicate vascular issues such as aortic dissection or arterial obstruction, not AF. D. Different apical and radial pulses is correct because atrial fibrillation often produces an irregularly irregular heartbeat. In AF, the ventricular contraction is inconsistent, so some heartbeats may not generate a palpable pulse at the radial site. This leads to a pulse deficit, which is the difference between the apical rate (counted at the heart) and the radial pulse (felt at the wrist). A pulse deficit is a classic sign of atrial fibrillation and should prompt immediate notification of the healthcare provider.