This study is a multi-center, prospective, randomized, double blind, placebo-controlled clinical trial. Subjects in the study will be adults with New York Heart Association (NYHA) Class II-IV heart failure (HF) due to left ventricular systolic dysfunction (LVSD), left ventricular ejection fraction (LVEF) <0.40, and secondary pulmonary hypertension (PH). The purpose of the study is to evaluate the safety, effectiveness, and effects of tadalafil compared to placebo on the subjects' functional capacity / quality of life.