A mild-to-moderate cough after open heart surgery is quite normal, according to HeartValveSurgery.com. Typically, the cough is related to some residual inflammation in the trachea from the trachea tube and resolves after a few weeks. A persistent cough may occur due to residual volume overload and is resolved with diuretics.
There are certain situations where coughs may be cause for concern in patients, according to HeartValveSurgery.com. A persistent cough can be common in older patients, but it may indicate an underlying lung issue, such as bronchitis or pneumonia. The site also states a nagging cough can be associated with the medication many patients take following surgery, such as ACE inhibitors.