•The patient does not respond to empirical therapy (ie, inotropes and intravenous diuretics) for heart failure
•The patient has a concomitant der (eg, COPD), and it is necessary to differentiate between pulmonary and cardiac causes of re tory distress.
•The patient has complex fluid status needs to be evaluated (eg, the patient continues to have periph- eral edema or ascites and has renal function param- eters indicating worsening prerenal azotemia)