The diagnosis of heart failure is often very difficult. Clinical history is often vague, and physical examination findings suffer from lack of specificity and sensitivity. For example, symptoms like shortness of breath and edema are often present in patients without cardiac disease, while elevated jugular venous pressure can be difficult to visualize and auscultation of a third heart sound can be challenging to hear, especially in an emergency room setting.

Although BNP levels can sometimes help clarify the clinical picture when patients present acutely with shortness of breath, patients both with and without heart failure may have BNP values that fall into a "gray zone", where the diagnosis is still very much in question. Also, there can be difficulties in interpreting BNP levels in patients with renal dysfunction, patients with a high body mass index, and patients of advanced age.

Investigative tests in the emergency department such as the electrocardiogram or chest x-ray are also non-specific for diagnosing heart failure. Tests such as echocardiography, while accurate in the assessment of left ventricular dysfunction, are expensive and are not always available on an emergent basis; furthermore, the presence of heart failure with normal systolic function (a.k.a. diastolic dysfunction) can complicate the interpretation of echocardiograms. Additionally, just because a patient has systolic dysfunction on an urgent echocardiogram does not mean that their acute dyspnea is due to heart failure, and so the test itself may not accurately reflect the acute situation at hand.

Another difficult diagnostic dilemma arises when a patient with a history of heart failure presents with signs that could also be consistent an acute respiratory illness such as pneumonia. Often, patients with background heart failure have elevated BNP levels at baseline. In this setting, chest radiographs can be especially difficult to interpret when one must distinguish between edema and infiltrates, or possibly both.

For all of these reasons, there is a pressing need for additional tools to help us differentiate heart failure from other causes of dyspnea in our acutely short of breath patients, and to improve our ability to provide accurate prognostic information and sound therapeutic management to our heart failure patients.