What finding might compromise the cardiac output readings in a client with left-sided heart failure?

In a patient with left-sided heart failure, premature atrial contractions (PACs) can significantly affect cardiac output readings. PACs are early depolarizations originating in the atria that can disrupt the normal rhythm of the heart. This disturbance can lead to ineffective atrial contractions, potentially resulting in reduced ventricular filling during diastole. When the atria contract prematurely, they may not allow adequate time for the ventricles to fill with blood, reducing stroke volume and subsequently impacting overall cardiac output.

While a regular sinus rhythm indicates stable electrical activity in the heart and typically supports effective pump function, PACs introduce variability that can hinder the heart's ability to maintain optimum output. Low blood pressure and high heart rate might also suggest compromised cardiac output, but those conditions do not inherently disrupt the rhythm and filling dynamics to the same extent as PACs. High heart rates generally signal increased output demand, whereas low blood pressure could reflect poor perfusion without directly impacting rhythm. Thus, PACs are particularly relevant in this scenario, as they directly interfere with the heart's rhythmic function and, consequently, cardiac performance.