The most appropriate treatment for this patient is to switch from her ACE inhibitor (lisinopril) to an angiotensin receptor blocker (ARB), such as valsartan, and observe her closely for several weeks to see if her cough resolves. For patients with heart failure, the two most common causes of a nonproductive cough are volume overload and ACE inhibitors. An ACE inhibitor–induced cough may occur at any time after an ACE inhibitor has been initiated, and it would not be surprising that she could develop an ACE inhibitor cough after 9 months of therapy. The most appropriate course of therapy, therefore, would be to switch to an ARB. Although data regarding mortality outcomes in patients with heart failure taking ARBs are limited, results thus far demonstrate equivalent mortality outcomes and fewer medication-related adverse events in this setting.

An echocardiogram evaluates left ventricular function and valvular abnormalities. It would not be helpful in a patient with diagnosed heart failure to assess for volume overload. Indications for repeating echocardiograms in patients with heart failure include a decline in functional status and to reassess function after uptitrating medications. Additionally, in patients followed over time, repeating an echocardiogram every 2 to 3 years is indicated to assess for further left ventricular dilation and evaluate left ventricular ejection fraction for further decline. It is unlikely to be helpful in this patient, who has no evidence of volume overload on examination and no pulmonary edema on chest radiograph.

B-type natriuretic peptide (BNP) level is useful for the assessment of acute dyspnea. Studies have shown that levels of BNP are elevated in patients with heart failure. Additionally, higher levels are associated with an increase in mortality. BNP has not been demonstrated to be useful to guide diuresis in patients with heart failure. In a patient with a history of heart failure, a random BNP level would not help in the assessment of fluid overload being the cause of a cough.

Pulmonary function testing is useful primarily in the evaluation of dyspnea or to assess for the presence of underlying lung disease that might contribute to cough, such as cough-variant asthma. However, this patient has no clinical history or increased risk for lung disease, is a never-smoker, and has a normal lung examination. Therefore, pulmonary function testing would not be appropriate prior to a trial of medication adjustment.