What is Pulmonary Embolism?
To summarize from the main pulmonary embolism article, pulmonary embolism happens when an artery or one of its branches in the lung is blocked. This blockage is usually caused by a blood clot that has traveled from another part of the body through the bloodstream, usually a leg (deep vein thrombosis or venous thromboembolism or DVT). Fat, air, or amniotic fluid can also cause a blockage.
When the blood flow through the lungs is obstructed, pressure is put on the right ventricle of the heart which is when symptoms such as shortness of breath and chest pain will start to appear.
Diagnosis
As with many conditions, doctors have been looking for ways to anticipate whether or not a patient has a certain set of risk factors that could result in pulmonary embolism. Some patients may be more susceptible than others. This would aid emergency room and family physicians decide whether further, more-invasive diagnostic tests are required.
In many cases, "pre-diagnosing" patients according to certain protocols has led to a diagnosis when other methods (CT scans or X-rays) tested negative. Investigators into alternative diagnostic protocols have found that 90% of blood tests and ultrafast CT scans used to diagnose pulmonary embolism come back negative.
Doctors and patients have become to rely on X-rays, CT scans, etc. to do the diagnosing. It is important to remember that sometimes a good discussion with your doctor about underlying factors will help him decide the next phase of diagnosis.
Establishing new diagnostic protocols have helped to lower overall costs to the health care system and to patients. A CT scan, for example, can cost up to $2,500.
Types of Pre-X-ray Diagnosis Protocols
There are three methods commonly used by doctors to assess whether or not a patient is a low-, medium-, or high-risk for blood clots and pulmonary embolism.
Pulmonary Embolism Rule-Out Criteria (PERC rule)
This set of criteria is used when a physician has already determined that a patient is at low-risk. There are 8 criteria that would flag a patient for further testing including:
1) younger than 50 years
2) a heart rate of less than 100 beats per minute
3) oxygen saturation greater than 95%
4) no prior history of deep venous thrombosis or pulmonary embolism
5) no trauma or surgery at least 4 weeks prior to onset of symptoms
6) no production or expectoration of bloody mucus
7) no taking of estrogen supplements
8) no unilateral leg swelling, a common clinical sign of DVT
If a patient has none of the above criteria, there is a less than 2% probability that the symptoms are caused by DVT or PE and so the patient would likely not benefit from further testing.
Jeff Kline, M.D., of the Carolinas Medical Center in Charlotte, N.C., established this protocol.
The Geneva Score
The Geneva Score and, as we will examine next, the Wells Score work with evaluating certain criteria and assigning each criterion a point level. The higher the total points, the higher the chances of DVT and PE. Patients with higher points will be investigated more thoroughly.
The Geneva Score has been revised since its introduction, the latest one being in October 27, 2008.
Criteria investigated include:
1) Over the age of 65
2) Previous DVT or PE
3) General anesthesia or fraction (1 month prior to onset of symptoms)
4) Active malignant condition or a malignant condition that has been cured (1 year prior to onset of symptoms)
5) Leg pain on one side
6) Production and expectoration of bloody phlegm
7) Pain on palpation to legs
8) A heart rate of 75-94
9) A heart rate of greater than 94.
The Geneva Score has been shown to be just as effective at determining risk as the Wells Score, but doesn't rely as heavily on the physician's experience to assess symptoms.
The Wells Score
A patient's Wells Score is determined by a number of criteria and, like the Geneva model, works through clinical examination and assigning of risk-factor ratings to each criterion. Doctors who use the Wells Score will look for (listed in order of importance/highest score):
1) Leg swelling and pain with palpation of the deep veins (clinical signs and symptoms of DVT)
2) Pulmonary embolism is a likely or more likely diagnosis than anything else
3) Heart rate of more than 100 beats per minute
4) Whether a patient has been confined to bed rest for at least 3 consecutive days prior to onset of symptoms; or has had surgery 4 weeks prior to onset of symptoms
5) Previous history of diagnosis of DVT or PE
6) Production and expectoration of bloody phlegm
7) Malignancy - where the patient is getting ongoing treatment, where treatment has been carried out in the 6 months prior to onset of symptoms, or patient is receiving palliative care
These screening methods are extremely effective in helping emergency room doctors, treating physicians, and family physicians in determining whether or not further investigation and/or treatment for DVT (deep vein thrombosis) or pulmonary embolism is warranted. All three methods have been shown to be extremely effective in decreasing the amount of X-rays and CT scans that for many patients aren't required, saving patients and hospitals money.
Sources: www.wikipedia.com; http://emcrit.org; www.medpagetoday.com; www.ncbi.nom.nih.gov (U.S. National Library of Medicine and National Institutes of Health); www.medscape.com; www.rhqn.org (Rural Healthcare Quality Network)