NPPB and atrial fibrillation: The major findings of this work are (i) CNPsp does not identify ACS in patients with chest pain or those with alternate disorders such as myopathies/valve disease as assessed by ROC AUC analysis; (ii) CNPsp levels are significantly elevated in patients presenting with AF, yet significantly lower in those with previous history of MI; (iii) if CNPsp measurement has any utility at all in ACS, it may possibly be found in assisting NT-proBNP-based risk assessment of future major adverse events.