Antihypertensive Agents/therapeutic use; Epoprostenol/analogs & derivatives; Hypertension, Pulmonary/drug therapy; Platelet Aggregation Inhibitors/therapeutic use; Pulmonary Embolism/complications; Thromboembolism/complications; Vasodilator Agents/therapeutic use; Aged; Antihypertensive Agents/administration & dosage; Antihypertensive Agents/blood; Cardiac Output/drug effects; Case-Control Studies; Chronic Disease; Epoprostenol/administration & dosage; Epoprostenol/blood; Epoprostenol/therapeutic use; Female; Follow-Up Studies; Humans; Hypertension, Pulmonary/blood; Hypertension, Pulmonary/etiology; Hypertension, Pulmonary/mortality; Infusion Pumps; Kaplan-Meier Estimate; Male; Middle Aged; Natriuretic Peptide, Brain/blood; Odds Ratio; Pain/drug therapy; Pain/etiology; Pain Measurement; Platelet Aggregation Inhibitors/administration & dosage; Platelet Aggregation Inhibitors/blood; Proportional Hazards Models; Prospective Studies; Pulmonary Embolism/blood; Pulmonary Embolism/drug therapy; Pulmonary Embolism/mortality; Risk Assessment; Severity of Illness Index; Thromboembolism/blood; Thromboembolism/drug therapy; Thromboembolism/mortality; Time Factors; Treatment Outcome; Vascular Resistance/drug effects; Vasodilator Agents/administration & dosage; Vasodilator Agents/blood; Walking