Aim: To investigate if a symptom driven referral for chronic thrombosis in the lungs after acute pulmonary embolism is better than the current approach.

Background: A number of patients with chronic thrombosis in the lungs after acute pulmonary embolism have dyspnea and reduced functional capacity without elevated pulmonary arterial pressure at rest (CTED). However, current guidelines for follow-up after acute pulmonary embolism will miss all patients with CTED, as referral for further examination is based on elevated pulmonary arterial pressure on echocardiography. Thus, the prevalence of CTED is unknown. The hypothesis is, that a symptom-driven referral of patients with previous acute pulmonary embolism is more sensitive in diagnosing CTED than the current approach.

Methods and materials: Patients diagnosed with acute pulmonary embolism in Region Midt (approx. 350 per year) will be screened for non-recovery or persistent pulmonary embolism related symptoms during their 3-6 months follow up at their local outpatient clinic. If the patient has persistent symptoms they will be referred to a scintigraphy. If CTED is suspected from the scintigraphy, the patient will be referred for full CTED work-up. The investigators expect to screen 300 patients for persistent symptoms with an expected study time of 3 years.

Inclusion Criteria:

• Acute PE diagnosed by CT or V/Q-scan within the last year.
• Non-recovery or persistent PE related symptoms assessed by a MRC breathlessness score or WHO functional class.
• Age >= 18 and < 80

Exclusion Criteria:

• Contraindications or unable to perform 6 minutes walk distance (6MWD) and/or cardiopulmonary exercise test.
• Contraindications to CT pulmonary angiography.
• Congestive heart failure (LVEF <40%).
• COPD or restrictive lung disease, severe or worse (FEV1 <50% and >=1 exacerbation causing hospital admission per year (GOLD grade 3 and 4 class C and D)).
• Lactating or pregnant.
• Unable or unwilling to provide written informed consent.
• Paroxysmal or persistent atrial fibrillation.
• Other known cause of PE related symptoms.