HF is a life-threatening condition in which the heart can no longer pump enough blood to the rest of the body. Symptoms of HF can include shortness of breath, nausea, fatigue, swelling of the feet or abdomen, and an irregular or rapid pulse. A critical challenge facing ED doctors is how to best manage people who come into the ED with symptoms of HF. Currently, most people evaluated for HF in the ED are admitted to the hospital; however, not all of these people are in need of such intensive treatment. It is estimated that up to 50% of HF-related hospital admissions could be avoided. Improving the ability of the ED doctor to effectively and safely manage low-risk HF patients is essential to avoid unnecessary hospitalizations. This study will gather information from ED patients at risk for HF to develop an algorithm decision tool that will predict patients' risk for inpatient or outpatient death and serious complications from HF. This decision tool will be distributed worldwide for ED use and will hopefully reduce the costs of HF care by appropriately allocating hospital resources.