A blood clot to the lung can be fatal and is one of the diagnoses that should always be considered when a patient presents with chest pain.
There is a classic presentation for pulmonary embolus with the patient complaining of pleuritic chest pain (hurts to take a deep breath), shortness of breath, and coughing up blood (hemoptysis); but more commonly patients can present with more subtle complaints, and the diagnosis may be easily and unavoidably missed.
Risk factors for pulmonary embolus include:
- prolonged inactivity like a long trip in a car or airplane,
- recent surgery or fracture,
- birth control pills (especially associated with smoking),
- cancer, and
Thrombophilia (thrombo=clot + philia= attraction) comprises a host of blood clotting disorders that place patients at risk for pulmonary embolus.
The pulmonary embolus begins in veins elsewhere in the body, usually the legs, though it can occur in the pelvis, arms, or the major veins in the abdomen. When a thrombus or blood clot forms, it has the potential to break free (now called an embolus) and float downstream, returning to the heart. The embolus can continue its journey through the heart and enter into the pulmonary circulation system, eventually becoming lodged in the branches of the pulmonary artery and cutting off blood supply to part of the lung. This decreased blood flow doesn't allow enough blood to pick up oxygen in the lung, and the patient can become markedly short of breath.
As mentioned above, the common complaints include:
- pleuritic chest pain from the inflamed lung,
- bloody sputum, and
- shortness of breath.
The patient can also have anxiety and sweat profusely. Depending upon the size of the clot, the initial presentation may be fainting (syncope) or shock in which the patient collapses, with decreased blood pressure and altered mental function.
Depending on the severity of the embolus and the amount of lung tissue at risk, the patient may present critically ill (in extremis) with markedly abnormal vital signs, or may appear rather normal. Physical examination may not be helpful, and the diagnostic studies are done upon clinical suspicion based on history and risk factors.
The diagnosis may be made directly with imaging of the lungs or indirectly by finding a clot elsewhere in the body. The strategy used to make a diagnosis will depend upon each individual patient's situation, but there are some general tools available.
D-dimer is a blood test that can measure breakdown products of blood clots in the body but cannot differentiate a pulmonary embolus from a healing scar from surgery, or a bruise from falling. If this test is negative, then a pulmonary embolus can usually be excluded if the patient is in a low risk category to form clots. Cancer and pregnancy are two other situations in which the d-Dimer test is often positive even without blood clots present.
Lungs can be imaged with a ventilation-perfusion scan or a CT scan to look for a clot. Each test has its benefits and limitations, and use of these tests is dependent upon the clinical situation. If there are technical issues so that the lungs cannot be imaged, an ultrasound of the legs may be performed to look for a thrombus; the concept is that if the symptoms are present of a pulmonary embolus and a clot is found in the leg, then the diagnosis can be inferred. However, if the complete clot has broken free, the leg ultrasound may be normal even when a pulmonary embolism is present.
Sometimes direct angiography of the pulmonary arteries may be performed. Catheters are placed into the pulmonary artery, and a dye is injected. This test must be performed by a specially trained radiologist or cardiologist.
The treatment for pulmonary embolus is anticoagulation using either heparin or enoxaparin (Lovenox) initially, and then transitioning to warfarin (Coumadin) for long-term treatment. The usual treatment course for anticoagulation for a pulmonary embolus is 3 to 6 months.
The lungs and heart can stop working if there is a large enough clot load. Thrombolytic, or clot busting, therapy may be considered in addition to the basics of oxygen, intravenous fluids, and medicines to support blood pressure. In rare and extreme cases, lytic agents may be directly injected into the area of clot.
Pulmonary embolus should always be considered a life-threatening illness.
For additional information, please read the Pulmonary Embolism article.