NPPB and atrial fibrillation: AHF is a fatal condition requiring hospital admission.[23] A preexisting comorbidity worsens the prognosis of heart failure.[4] The presence of comorbidity can potentially lead to overestimation (renal failure, hyperthyroidism, inflammation, atrial fibrillation, old age, and female sex) or underestimation (obesity, pericardial effusion, and recent acute coronary syndrome) of BNP levels.