A client with a recent exacerbation of heart failure reports to the nurse feeling uncomfortable and anxious, with a sensation of the flopping in the chest. While waiting for an electrocardiogram (ECG), which assessment is most important for the nurse to obtain?

A. The degree of skin elasticity is not the most immediate concern in this context. B. Length of capillary refill is important but does not provide specific information regarding the client's cardiac rhythm or possible arrhythmias. C. The volume of pedal pulses can provide information about peripheral circulation but is less critical than assessing the heart's rhythm. D. Assessing the rhythm of the apical pulse is crucial because the client’s symptoms suggest possible cardiac arrhythmia, which needs immediate attention.