What is Pulmonary Embolism?
Pulmonary embolism is a clinical condition in which blood clots formed in the venous system of our body migrate from the local site through the right atrium and right ventricle to the pulmonary vasculature. Most of these thrombus arise
from the deep vein thrombosis of lower extremities. Pulmonary embolism is a serious clinical condition with high morbidity and death rate( mortality)
What are the causes of Pulmonary Embolism?
Main cause of pulmonary embolism is the blood clot formed in the deep vein of our body( lower extremities, upper extremities, pelvic veins etc) which migrate from the origin site to the pulmonary blood vessels and cause the blockade in pulmonary arteries or their branches. Besides blood clot the other cause of pulmonary embolism are: fat embolism( femoral fracture), foreign body injection in venous system, amniotic fluid embolism( pregnant patients or during the labor), air embolism( from central line catheters), tumor pieces of debris etc.
Classification of Pulmonary Embolism
- Minor Pulmonary Embolism: This is the most common one in which the emboli is in subsegmental branches of pulmonary vasculature. Patients are stable and present with back pain and exercise dyspnea. Anticoagulation therapy is enough and doesn’t require any intervention therapy or thrombolytic therapy.
- Submissive Pulmonary Embolism: Emboli is in major branches of pulmonary arteries and patients have signs of right heart failure: increase in pro-bnp( marker of heart failure), increase in cardiac troponin( marker of damage in heart tissue), right heart dilatation etc but with normal blood pressure and no signs of cardiogenic shock. Patients with high mortality are treated either with thrombolytics or catheter directed pharmacological and mechanical therapy.
- Massive Pulmonary Embolism: This emboli is in the main pulmonary
trunk and proximal of right and left pulmonary arteries and the patient is in cardiogenic shock with low blood pressure and sign of hypoperfusion. The mortality in this group may be as high as %60 and the patient should be promptly diagnosed and treated with either thrombolytic therapy or catheter directed pharmacomechanical therapy. Contrast Pulmonary CT
Angiography is the modality for diagnosis. In unstable Patients, echocardiographic sign of right heart failure, dilated right heart and pulmonary hypertension( Systolic pulmonary artery pressure up to 60 mm hg) is enough for the diagnosis and initiate therapy.
What are the signs and symptoms in Pulmonary Embolism?
The signs and symptoms depend on the dimension of the embolus, the pulmonary capacity and performance of the patient and whether the emboli has blocked the major pulmonary arteries or not.
In a minor pulmonary embolism patient may experience exercise intolerance, back pain, pleuritic chest pain( pain in deep inhalation), hemoptysis( blood in spit or cough), subfebrile fever, tachycardia etc.
In a submassive or massive pulmonary embolism patient may experience severe dyspnea in rest, chest and back pain, hypotension, peripheral hypoperfusion, sudden circulatory collapse and sudden cardiac death.
How is Pulmonary Embolism diagnosed?
Suspicion is the key in diagnosis of pulmonary embolism. Firstly whenever a patient presented with the symptoms suggestive of pulmonary embolism, the risk factors for pulmonary embolism are sought eg: having major surgery recently, fracture of lower extremities, immobile patients, patients with genetic disorders predisposing to embolism, presence of cancer, patients not using anticoagulation therapy after surgery( cranial, renal surgery etc). Then certain tests are done to confirm the diagnosis. The main tests are:
- Doppler ultrasonography of lower extremities veins: It is used to determine the presence, extension and nature of thrombus( acute, subacute and chronic)
- D-dimer test: D-dimer is a protein fragment released because of fragmentation of thrombosis. Its level is increased in pulmonary embolism but can be elevated in many other clinical conditions like after surgery, myocardial infarction, aortic dissection, pregnancy, infection, pneumonia etc. So the specificity of d dimer is low and positive value
should be confirmed by other diagnostic tools. Negative D-dimer test can be used to rule out pulmonary embolism in low risk patients.
- Echocardiography: Echocardiography is normal in minor embolism but in massive and submassive embolism echocardiography may show right heart dilatation, elevation in pulmonary artery pressure, right heart failure etc. Signs of severe right heart impairment is also a sign of a high risk patient and helps us to decide the therapy to be choosed.
- Computer Tomography: Contrast Enhanced Pulmonary CT Angiography is the standard test to diagnose the presence and extension pulmonary embolism. It also gives us ideas about right heart dilatation
and helps to guide therapy.
Treatment in Pulmonary Embolism
.Medical Therapy: Anticoagulation therapy is the mainstay in the treatment of pulmonary embolism without hemodynamic compromise and shock. Anticoagulation therapy does not dissolve the preformed thrombus but prevents the thrombus from extending and getting bigger. High risk patients with massive pulmonary embolism and with hemodynamic shock or signs of severe impairment in right heart function should be treated with thrombolytic therapy.
.Catheter Directed Thrombolytic Therapy: Systemic thrombolytics used in pulmonary embolism carries substantial risk of intracranial bleeding. However with the use of catheter and injection of thrombolytic in the pulmonary arteries, a little fraction of the systemic dose is enough for similar efficacy. In this way we can minimize the bleeding risk while maintaining the same efficacy.
.Pharmacomechanical Thrombectomy: In this procedure catheters advanced to the pulmonary thrombus are used to aspirate the thrombus and then thrombolytic therapy is injected along with ultrasonic waves. ( EKOS system) These ultrasonic waves enhance the effect of thrombolytics by increasing the thrombus permeability and lytic penetration of the drug. This can be used within 14 days after the onset of symptoms but the success rate is high in early presenting cases.