A nurse is reviewing laboratory results for a client who has atrial fibrillation. Which of the following blood test results should the nurse understand can be a possible cause of atrial fibrillation?

A. Elevated erythrocyte sedimentation rate (ESR): ESR is a nonspecific marker of inflammation; while inflammation is associated with arrhythmias, ESR itself is not a common direct cause of atrial fibrillation. B. Elevated thyroid-stimulating hormone (TSH): An elevated TSH indicates hypothyroidism; atrial fibrillation is more commonly caused by hyperthyroidism (which produces a low TSH). C. Elevated C-reactive protein (CRP): CRP is an inflammatory marker and is associated with higher risk of AF, but it is not typically described as a direct cause in routine clinical testing—it's a risk/association marker. D. Elevated brain natriuretic peptide (BNP): Elevated BNP indicates cardiac stretch/heart failure; structural heart disease and heart failure are common precipitants/causes of atrial fibrillation, so an elevated BNP can reflect an underlying condition that leads to AF.