The most appropriate next step in management is a trial of a proton pump inhibitor (PPI). This patient has classic symptoms of gastroesophageal reflux disease (GERD) in the form of heartburn. Symptoms of heartburn and regurgitation are strong predictors for the clinical diagnosis of GERD. The most appropriate next step in a patient without alarm symptoms (dysphagia, unintentional weight loss, hematemesis, or melena) is an empiric trial of a PPI.

Although ambulatory esophageal pH monitoring is the most accurate technique to diagnose GERD, it is expensive and invasive and is therefore only indicated in patients whose symptoms have not responded to medication. This patient has never taken a PPI previously to control his symptoms, so pH testing is not needed at this point in management.

Esophageal manometry measures the pressure levels in the esophagus and is useful in evaluating esophageal motility disorders such as achalasia. However, this patient has not had dysphagia to solids and liquids, which makes an esophageal motility disorder unlikely.

This patient has not had any alarm symptoms such as difficulty swallowing or weight loss that would warrant an upper endoscopy at this time. An upper endoscopy would be necessary if this patient had alarm symptoms or if his symptoms did not respond to the empiric trial of a PPI.