1. Given the pt’s history and physical exam list your differential diagnosis including at least 5 possible diagnoses. (Remember the differential diagnosis should be broad and really just include causes that could account for the relevant symptoms) Essentially what could account for acute onset dyspnea, chest pain, and tachypnea.
Pulmonary embolism (PE)- classic PE triad is dyspnea, hemoptysis, and chest pain
Pneumonia- wheezing, difficult and rapid breathing, fever, chest pain
Acute bronchitis- wheezing, rapid labored breathing, chest pain (due to her asthma, all of these would worsen in intensity)
Heart failure- dyspnea, chest pain, orthopnea, swelling of the ankles or legs
Lung cancer- can present with a variety of symptoms including dyspnea, chest pain, rapid breathing, cough, hemoptysis
2. Now given the clinical presentation, physical exam and labs What is your top diagnosis? (Use your differential and think through what data lead you to believe your top diagnosis is correct and go against the others)
Pulmonary embolism is the most likely diagnosis. The classic triad of symptoms for a PE were described- dyspnea, chest pain, and hemoptysis. The patient has a history of deep vein thrombosis (DVT), a blood clot that forms in the deep veins of the body, and it is usually found in the legs. This patient has swelling and tenderness in the right leg which is very likely from a DVT that developed while the patient was inactive on her flight. She is taking an oral contraceptive which usually increases the chance of a blood clot. Also, her ECG showed sinus tachycardia, which is another symptom that occurs in about half of cases. Her normal levels of troponin I suggest that there are no problems with her heart, as troponin would be released in the case of injury to the heart tissue. It is unlikely that the patient is suffering from a severe lung infection that would cause her symptoms, because her procalcitonin levels were normal, and increased levels would suggest a bacterial infection or sepsis. Therefore, bronchitis is likely out for a diagnosis, because a lung infection would be the most likely cause for an asthmatic patient of this age and health. Pneumonia and lung cancer could be diagnosed by a chest x-ray, but the x-ray was normal. Also, the white blood count would likely be higher. A PE is incredibly likely, and it would not be visualized by a chest x-ray, so it pairs with the normal chest x-ray. Lastly, a normal D-dimer is equal to or less than 250 ng/ mL, and the patient’s D-dimer was 2000 ng/ mL. The D-dimer test checks for a protein that remains after the breakdown of a blood clot, so a level of 2000 would suggest this patient had a blood clot.
3. Given your top diagnosis what specific tests do you need to run in order to confirm it?
A variety of tests can be done to confirm the diagnosis. A CT angiogram (a CT with dye) can be done to visualize clots in the lungs or legs. A lung ventilation/ perfusion scan, or VQ scan can detect a PE and uses a radioactive substance to show how oxygen and blood are flowing to areas of the lungs. Also, a pulmonary angiography can be done. This inserts a catheter through the groin to blood vessels in the lungs, dye is injected, and then the dye is visualized using an x-ray.
4. Results of a VQ Scan are shown below. Before interpreting the results below please elaborate on the following:
· a.What is the ventilation perfusion ratio (V/Q ratio)? (Include a short discussion on hypoxic vasoconstriction)
The ventilation/ perfusion ratio is a measurement of the air that reaches the alveoli divided by the blood that reaches the alveoli. This ratio can be a signal to what is going on in the lungs. For example, when the V/Q ratio is low caused from either too much blood or too little ventilation, hypoxic vasoconstriction can occur and direct blood to other parts of the lungs. In the case of a PE, the V/Q ratio will be decreased in the parallel blood supplies of the vessel blocked by the clot. Hypoxic vasoconstriction will occur and decrease the amount of blood perfusion in order to get the arterial blood gases back to normal.
· b.What is a V/Q defect? Does a regional V/Q mismatch normally exist in the lungs? What does it tell you? What do you expect for this situation? (Include short discussion of west zones)
A V/Q defect is an abnormal total ventilation/ perfusion ratio of the lung. The normal upright lung does usually have some regional variation in the total V/Q ratio. The perfusion increases from the top to the bottom in the standing position. Of the four West zones, zone 1 is not found healthy lung. Zone 1’s alveolar pressure is higher than the arterial or venous pressure, and so they collapse the vessels around them and causes alveolar dead space. In zone 2, alveolar pressure is more than venous pressure but less than arterial pressure. In zone 3, alveolar pressure is less than both the arterial and venous pressure; this zone makes up the majority of the healthy lung. Zone 4 is seen often pulmonary edema where the interstitial pressure is higher than alveolar or venous pressure. Since zone 3 receives the best perfusion and makes up the majority of the healthy lung, it is likely that this may be a location for the PE since the patient’s symptoms are severe.
· c.What is a V/Q scan? How is it performed?
A VQ scan is a lung ventilation/ perfusion scan where the ventilation part of the test shows where air flows in the lungs and the perfusion part of the test shows where blood flows in the lungs. Both parts use radioisotopes. For ventilation the radioisotopes are inhaled, while for perfusion radioisotopes are injected into the blood, and then a gamma camera is used to visualize how air and blood are moving.
· d.How would O2 help this patient and how would it change the V/Q ratio?
Oxygen therapy will do little to help with area of poor perfusion, but it will increase the amount of oxygen uptake from the areas that have good perfusion. Also, if blood is being shunted from the blocked vessel of the PE to parallel routes, then increased oxygen in those areas can be taken up by the extra blood. In this way, oxygen therapy should help the patient get more oxygen and function better. Since the oxygen will increase ventilation, the V/Q ratio should increase.
· e.What is the interpretation of the scan below (Fig 1)? Match this up with the clinical findings.
For a pulmonary embolism, the VQ scan should show essentially normal ventilation with defects in perfusion to the lungs. The VQ scan shows a darker gray in the right lung, which suggests slightly better ventilation in the right lung than the left. This makes sense with the wheezing of the left lower lung. The VQ also shows multiple perfusion defects in the left lung (bottom left picture) since it is barely a smudge of gray. From this, one could conclude that the pulmonary embolism is the blood supply for the left lung.
Lung Scintography
5. Given the positive diagnosis and confirmation of your suspicions what additional tests might be indicated in this patient. Why is that important (Hint: Where did the embolus come from? There was a clinical finding and a major criteria of well’s score that would indicate further testing)
Since the embolus likely came from a deep vein of the right leg, an ultrasound of the leg or other visual testing should be done to verify that was the origin of the clot. The source of the clot is important in order to treat and prevent further problems. Not only could the patient have another PE since she has a history of DVT, but she could also suffer from a stroke caused by a clot thrown to the vessels of the brain. Also, if the clot came from atrial fibrillation, that can often be treated with anticoagulants alone, whereas a clot from an extremity like a DVT may require a larger variety of treatment. Since the patient has already had the D-dimer test, which would usually be done after evaluation of the patient’s risk of PE (well’s score), the next step would have been CT angiogram or VQ scan to confirm the diagnosis. Usually the patient would be categorized with a Well’s score before receiving a D-dimer test. The Well’s scoring system or prediction rule gives certain points for characteristics of a PE to calculate the probability of a PE. This patient scores at a 10 when calculated, which would be a high probability of a PE. Depending on the severity of the pulmonary embolism, it can present in different ways, and therefore there can be some variety in the treatment. In most cases, a VQ scan or CT angiogram would be done to confirm the diagnosis (VQ scan was done). The next step would be to use ultrasound to confirm the location of the clot before treatment.
6. What do we do now that we have the diagnosis? What is the mainstay treatment for a PE? Does this actually remove the clot? There are newer treatment modalities available what is the evidence for these? (Hint: Einstein PE trial)
Anticoagulants have been the mainstay treatment for PEs, but there are are other treatments for pulmonary embolism. Patients will often be given oxygen to increase the amount of oxygen during ventilation, in order to help with uptake by the blood that is able to perfuse. Anticoagulants such as warfarin, heparin, and enoxaparin can be used. The patient can also be given thrombolytic drugs that help to break up the clot such as reteplase. It should be noted however that depending on the severity of the pulmonary embolism it can present in different ways, and therefore there can be some variety in the treatment. For example, IVC filters or devices that act as a “catcher’s mitt” to catch clots before they move to a more dangerous location used to be highly suggested for prevention. More recently, they have been subjects of lawsuits as they have had a tendency to move to more dangerous locations, and are now only suggested for those who have had problems with anticoagulants or other contraindications (approved by ACCP and the FDA). Lastly, a catheter can be inserted to suck up the blood clot. Anticoagulants only prevent further clot forming, while thrombolytics help to break the clot into pieces. Using a catheter is the only way to remove the clot. A new treatment for PEs is a drug called rivaroxavan. This oral drug is a Factor Xa inhibitor; Factor X is a necessary component of the clotting cascade, and an inhibitor of this factor has been shown to treat PEs and DVTs with much success.
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