Most clots come from pelvic and abdominal veins
Here because of less circulation when you have a sedentary job or state (think about the Virchow's triad)
If formed here, moves up to inferior vena cava, heart and pulmonary artery where they get stuck

Effects of pulmonary embolism:
- Results in lung tissue that is ventilated but not perfused which produces an intrapulmonary dead space and impaired gas exchange
- increased pulmonary resistance
- haemodynamic consequences

Classification:
Three types

Small/medium thrombosis
Massive pulmonary embolism

Or
Acute vs non acute

Or
Stable vs unstable (source: Dtsch Arztebl Int. 2010 Aug; 107(34-35): 589–595.
Published online 2010 Aug 30. doi: 10.3238/arztebl.2010.0589)
Hemodynamically unstable patients are considered to have high-risk PE, whereas hemodynamically stable patients are considered to have non-high-risk PE. After classification into one of these two risk groups, patients undergo further diagnostic evaluation for PE according to the appropriate risk-adapted algorithm. Patients who are in cardiogenic shock or have persistent arterial hypotension (high-risk PE) should undergo multidetector computed tomography (MDCT) or echocardiography at once, so that a PE, if present, can be treated immediately by thrombolysis. For hemodynamically stable patients with non-high-risk PE the proper diagnostic strategy is determined by the clinical probability of PE, which can be calculated with the aid of validated scoring systems and is based on both MDCT and D-dimer levels. For further risk stratification in hemodynamically stable patients, tests are performed to detect right ventricular dysfunction or myocardial injury, either of which indicates intermediate-risk PE. In addition to specific therapy, patients with high-risk PE, patients at high risk for hemorrhage and these with severe renal insufficiency should be anticoagulated with unfractionated heparin. All other patients should be treated with low-molecular-weight heparin or fondaparinux. Thereafter, long-term oral anticoagulation with vitamin K antagonists is recommended.

Risk factors of pulmonary embolism
- Clinical signs and symptoms (such as swelling, heartrate, immobilsation)
- Already having had PE
- Haemoptysis
- Check the algorythm 
- take into account pregancy
- D dimer
   
Investigations

Radionuclide ventilation/perfusion scanning V/Q (pregant women can recieve it but recieve a lower dose and at a certain point)
It is performed in a special clinic
CTA scan is done (contrast is given and look where the blood stops)

Acute management is to solve the problem 
- could be antigoaculant