Pulmonary Embolism

What is Pulmonary Embolism?

Pulmonary embolism (PE) refers to a blood clot that travels to the lung from another part of the body. The clot lodges in the pulmonary arteries and prevents blood from normally flowing through the lung to pick up oxygen. So, as a consequence, PE causes low oxygen or “hypoxemia”. If a PE is large enough or if there are enough small emboli, hypoxemia can be severe, and blood pressure can even drop to life threatening levels.

Blood clots almost always come from clots that form in large veins outside of the lungs, usually in the major veins of the legs. Occasionally blood clots can come from the right side of the heart. When blood clots form in veins, the process is called “deep venous thrombosis”, aka, DVT. When those clots break off and go to the lung (into which all venous – or used, de-oxygenated blood flows), the condition is called “venous thromboembolism”, aka, VTE. Not all blood clots that form in veins break off and cause VTE, but a good many do.

Why does DVT occur?

  1. When blood flow slows down substantially, it tends to clot. Blood flow through the body is normally slowest in the calf veins of the legs. If something slows that flow down even further, such as mechanical compression of the leg veins by a leg cast, then a clot can occur.
  2. Sometimes, seriously ill patients (usually in the hospital) have catheters placed into large veins in the legs, or upper body. Those catheters can cause clots to occur in the vein.
  3. Some diseases, most notably cancer, cause the body’s blood clotting system to go off track and form clots in veins.

Symptoms of PE include abrupt shortness of breath, chest pain, occasional cough or hemoptysis (coughing up blood), rapid heart beating, abrupt light headedness or even passing out, distress and anxiety.

Diagnosis of DVT is made by an ultrasound test. Diagnosis of PE is made by special X ray tests which include Computerized Tomography Scanning (CT), or Ventilation Perfusion Scanning (V/Q).

Therapy consists of blood thinners and is usually very effective. But early treatment is very important because VTE can be life threatening.