This project aims to evaluate a rehabilitation program as treatment and uncover potential pathophysiological mechanisms of a newly identified chronic condition named "Post Pulmonary Embolism Syndrome" (PPS).

The newly identified Post Pulmonary Embolism Syndrome (PPS) is characterized by chronic persistent, but unexplained dyspnea (i.e. without signs of pulmonary hypertension or pulmonary abnormality). Symptoms are considerable, but less severe than in CTEPH patients. A recent study performed by our group confirmed that up to 50% of our patients complained of various grades of persistent unexplained dyspnea 1-10 years after the diagnosis of PE.

In this multifaceted project we wish to evaluate the effect of an eight week rehabilitation program led and supervised by a trained physiotherapist on exercise capacity in PPS patients. This interventional part of the study will be formed as a randomized controlled trial. Patients will be randomized to either usual care or a physiotherapist-supervised rehabilitation program.

The study also aims to explore potential underlying pathophysiological mechanisms in PPS, using state of the art methods such as cardiac magnetic resonance imaging and transthoracic echocardiography involving novel methods focusing on the right ventricle. The pathophysiological part of the study will be formed as a case control study, where post PE-patients who do not fulfill the criteria for PPS will serve as controls.

Inclusion Criteria:

• Objectively diagnosed symptomatic pulmonary embolism by CTPA or high-probability scintigraphy 6 months to 6 years before inclusion
• Persistent dyspnea defined as modified Medical Research Council (mMRC) breathlessness scale >= 1 that has appeared or worsened after the diagnosis of PE (eligibility criteria for randomization)

Exclusion Criteria:

• Significant pulmonary disease (COPD GOLD >= 2, restrictive pulmonary disease, lung cancer or pleural disease.
• Heart failure (either HFrEF, HFmrEF or HFpEF as defined in ESC guidelines)
• Significant valvular heart disease
• Chronic thromboemboli pulmonary hypertension (CTEPH)
• Patients unfit for rehabilitation or walking tests du to old age, physical disability or disease
• Patients with a history of poor compliance or any condition that would interfere with the ability to comply with the study protocol e.g. history of drug abuse, excessive alcohol beverage consumption, cognitive dysfunction or severe psychiatric disease
• Active malignancy
• Life expectancy less than 3 months
• Pregnancy