Difference Between PE and DVT

The key difference between PE and DVT is that, in PE (pulmonary embolism), the occlusion occurs in the pulmonary vessels by a thrombus that forms in the right heart and systemic veins getting dislodged and deposited in the pulmonary vessels while, in DVT (deep vein thrombosis), the occlusion occurs in the deep veins of the leg by a thrombus.

CONTENTS

1. Overview and Key Difference
2. What is PE 
3. What is DVT
4. Similarities Between PE and DVT
5. Side by Side Comparison – PE vs DVT in Tabular Form
6. Summary

What is PE?

Pulmonary embolism or PE is the process where the thrombi formed in the right heart and systemic veins get dislodged and deposited in the pulmonary vessels. The femoral veins are the commonest source of emboli.

Occlusion of an artery by an embolus ventilates, but not perfuse, the area of the lung that gets the supply from the particular artery. This ultimately results in a dead space impairing the gas perfusion. Eventually, the under-perfused area of the lung collapses due to the reduced surfactant production. But the infarction of that region is unlikely because of the dual blood supply coming to the pulmonary tissues via the bronchial vessels.

Small Pulmonary Embolism

When the embolus occludes a terminal vessel, the patient develops pleuritic chest pain and breathlessness. About three days after, the patient can also develop hemoptysis. However, rarely, a patient gets fever.

Massive Pulmonary Embolism

This is a rare condition where the lungs collapse, owing to an obstruction in the vessels through which the blood flows out of the right ventricle. Thus, the patient gets severe central chest pain and, also appears sweaty and pale.

When there are multiple recurrent emboli, the patient gets dyspnea, which progressively worsens over few weeks. In addition, there are also other symptoms such as syncope on exertion, weakness, and angina.

Clinical Features

A vast majority of the pulmonary emboli develop silently. However, the other symptoms include;

• Sudden onset of dyspnea
• Pleuritic chest pain
• Cough
• Hemoptysis, if an infarction has happened

Investigations

The following investigations help confirm any clinical suspicion of pulmonary embolism and to estimate the extent of obstruction.

• Chest x-ray
• ECG
• Blood tests such as full blood count, PT/INR
• Plasma D-dimer
• Radionuclide ventilation/ perfusion scanning
• USS
• CT
• MRI

Management

High flow oxygen is necessary for all the patients, along with analgesia and bed rest. It is equally important to use anticoagulation therapy using heparin followed by warfarin. In case of a massive pulmonary embolism, intravenous fluids have to be administered appropriately. If necessary, inotropic agents can also be given. Fibrinolytic therapy and surgical embolectomy are the other options available. Furthermore, anticoagulation therapy with warfarin should be continued to prevent the future development of emboli.

What is DVT?

Deep vein thrombosis or DVT is the occlusion of a deep vein by a thrombus. DVT of the legs is the commonest form of DVT, and it has an alarmingly high rate of mortality.

Risk Factors

Patient factors

• Obesity
• Increasing age
• Pregnancy
• Varicose veins
• Use of oral contraceptive pills
• Family history

Surgical conditions

• Any surgery lasting for more than thirty minutes

Medical conditions

• Myocardial infarction
• Malignancy
• Inflammatory bowel disease
• Nephrotic syndrome
• Hematological diseases
• Pneumonia

Clinical Features

The lower limb DVT typically starts in the distal veins and clinical features of this condition typically include,

• Pain
• Swelling of the lower limbs
• Increased temperature in the lower limbs
• Dilatation of the superficial veins

Although these symptoms frequently appear unilaterally it is possible to also have them bilaterally. But bilateral DVT almost always involves malignancies and abnormalities in the IVC.

Whenever a patient presents with the aforementioned symptoms, it is necessary to take the risk factors of DVT into consideration. During the examination, special attention should be given to identifying any malignant conditions. Since it is possible to have pulmonary embolism together with DVT, it is also important to check for signs and symptoms of pulmonary embolism.

Moreover, medical professionals use a set of clinical criteria called the Wells score to rank the patients according to their likelihood of having DVT.

Investigations

Most importantly, the choice of investigations depends on the Wells score of the patient.

• D dimer test is for patients with a low probability of DVT. If the results are normal, there is no need of doing more investigations to exclude DVT.
• Patients whose D dimer test results are high as well as patients with a moderate to high probability have to undergo compression ultrasound.

At the same time, it is very important to carry out investigations to exclude any underlying pathology such as pelvic malignancies.

Management

Management includes anticoagulation therapy as the mainstay, together with elevation and analgesia. Thrombolysis should be considered as an option only if the patient is in a life-threatening In the anticoagulation therapy, LMWH is initially administered and is followed by a coumarin anticoagulant such as warfarin.

What is the Similarity Between PE and DVT?

• Both PE and DVT are due to the occlusion of blood vessels by a thrombus or an embolus.

What is the Difference Between PE and DVT?

Summary – PE vs DVT

In summary, PE is the condition where thrombi formed in the right heart and systemic veins get dislodged and deposited in the pulmonary vessels. DVT, on the other hand, is the occlusion of the deep veins of the legs due to the formation of thrombi. Accordingly, in PE, the occlusion is inside a pulmonary vessel, while, in DVT the occlusion is within a deep vein of the leg. Thus, this is the main difference between PE and DVT.

Reference:

1. Kumar, Parveen J., and Michael L. Clark. Kumar & Clark clinical medicine. Edinburgh: W.B. Saunders, 2009.

Image Courtesy:

1. “3177360” (CC0) via Pixabay
2. “DVT “Deep Vein Thrombosis” “Ultrasound Image”” by Mr Thinktank (CC BY 2.0) via Flickr