Can a common ED drug improve lung blood pressure?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * group 2 pulmonary hypertension with CpcPH with PVR equals or more than 4 by RHC. * NYHA II-III symptoms. * Patients should be on HF medical therapy 90 days before enrollment in the study. Exclusion Criteria: * All groups of PH, other than Group 2 PH. * Patients with Group 2, but no meeting the predefined hemodynamic criteria for CpcPH (mean PAP more than 20 mmHg, mean PCWP more than 15 mmHg, PVR equals or more than 4 WU). * Hypersensitivity, allergy, or intolerable side effects of PDE-5 inhibitors. * Contraindication to PDE-5 inhibitors, including current nitrate therapy. * Anticipated cardiac resynchronization therapy within 3 months of enrollment. * History of heart transplant, ventricular-assist device, or any other solid-organ transplant * Recent stroke, myocardial infarction, any coronary intervention; PCI or CABG. * Decompensated heart failure. * Female subject who is pregnant, breast-feeding, or unwilling to practice an acceptable method of birth control unless postmenopausal or sterile. * Unreliability as a study participant, based on the investigator's (or designee's) knowledge of the subject (e.g., alcohol or other substance abuse, inability or unwillingness to adhere to the protocol, documented noncompliance, or vulnerable population) * Current enrollment, or enrollment completed \<30 days previously, in another investigational drug or device clinical study. * Undergoing dialysis for end-stage renal disease. * End-stage liver disease comorbidities, limiting exercise tolerance. * Morbid obesity (body mass index \> 40). * Severe peripheral vascular disease with intermittent claudication. * Status after amputation of lower extremity(s) at any level. * Severe degenerative joint disease preventing normal walking. * Cerebrovascular accident with long-term sequelae affecting ability to walk.