ADHF may be a manifestation of any abnormality of cardiovascular function. Most patients have a prior history of heart failure. Patients with chronic heart failure may have a history of gradually worsening symptoms of pulmonary and systemic venous congestion over several days to weeks or may have more rapid development of symptoms commonly associated with a clear precipitant (examples: new onset atrial fibrillation with rapid ventricular response in a patient with HFpEF; ACS in a patient with an ischemic cardiomyopathy). Approximately 25% of patients with ADHF have new onset or de novo heart failure—many of these patients have associated ACS or poorly controlled hypertension (Adams KF, Fonarow GC, Emerman CL, LeJemtel TH, Costanzo MR, Abraham WT, ADHERE Scientific Advisory Committee and Investigators et al. Am Heart J149(2):209–216, 2005).