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Pulmonary Clinical Case Study Three

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Case 3

Case Three: Pulmonary Embolism

Differential Diagnoses relating mostly to acute onset dyspnea, chest pain, and tachypnea:

  • Pulmonary Embolism
  • Cardiac Ischemia
  • Heart Failure
  • COPD exacerbation
  • Pneumothorax
  • Pneumonia
  • Acute Anxiety with hyperventilation

Top Diagnosis: Pulmonary Embolism due to the leg swelling, previous history of deep vein thrombosis, and chest pain. 

  • Cardiac ischemia and heart failure ruled out due to regular EKG and troponin levels.
  • Pneumonia and pneumothorax ruled out for normal chest X-Ray with no acute findings.
  • Acute anxiety with hyperventilation ruled out due to normal blood oxygen levels.
  • COPD exacerbation ruled out due to normal chest X-Ray and normal ventilation.

Recommended Tests: CT angiography, V/Q scanning

  • CT angiography visualizes the blood vessels and can be used to detect blood vessels, particularly in the pulmonary vessels in this case. 
  • V/Q scanning shows the perfusion and ventilation of all various parts of the lungs. Blood clots would afffect the perfusion as the blood flow would be decreased in areas with pulmonary embolism. 

Ventilation-Perfusion Ratio

  • The ventilation perfusion ratio is the ratio of the air in the alveoli to the blood supply to the alveoli. This changes based on the height of the alveoli, pulmonary vessels, and intrapleural pressure all due to gravity. Hypoxic vasoconstriction is when the blood vessels constrict due to hypoxia (low blood oxygen) without hypercapnea (high blood carbon dioxide). The blood is redirected to alveoli with higher oxygen concentrations. 

Ventilation-Perfusion Defect and Mismatches

  • V/Q defects are abnormalities in the total ventilation-perfusion ratio of the lung that causes defects in oxygen concentrations in the blood. 

  • V/Q mismatch normally occur in the lungs as the top of the lungs (zone 1) usually have a high V/Q and high ventilation. The bottom of the lungs (zone 2) has a low V/Q and high blood flow. The middle of the lung (zone 3) has moderate V/Q ratio and similar perfusion and ventilation.  

  • This situation is that the embolism will cause a decrease in perfusion, as it will block the blood vessel. This decrease in perfusion will cause decrease in ventilation at the alveoli. .

V/Q Scan

  • V/Q scan is a nuclear medicine scan that uses radioactive material to measure perfusion and ventilation in the lungs. First, the radioactive material is breathed in and scans are taken of the lungs. Second, a different radioactive material is injected into the veins and more scans of the lungs are taken. The two sets of scans are compared.

Oxygen and its Effect on V/Q Ratio

  • An increase of O2 would decrease the hypoxic vasoconstriction and increase the perfusion to the alveoli. Dilation would increase the blood flow (Q) and thus decrease the V/Q ratio. 

V/Q Scan Interpretation

  • There is a lack of perfusion or blood flow in the right lung. The Post perfusion scan showed an unequal distribution of blood flow. Ventilation is uniform and normal. 

Additional Tests 

  • D-dimer testing for D-dimer levels from intrinsic fibrinolysis. High levels of D-dimer would indicate a recent thrombus. Thrombi would test for the patient’s deep vein thrombosis. Thrombi detach from the blood vessel and become emboli that become lodge in pulmonary vessels, creating a pulmonary embolism. 

  • Duplex ultrasonography uses Doppler ultrasonography to detect low compressibility of the veins or decreased blood flow in the veins. These are indicative of deep vein thrombosis. Thrombi detach from the blood vessel and become emboli that become lodge in pulmonary vessels, creating a pulmonary embolism. 

Treatments for Pulmonary Embolism

  • After diagnosis, focus on treatment of patient. 

  • Mainstay treatment is anticoagulation. It does not remove the clot but prevents further clotting and extension of the clot. Treatment also includes support treatment such as increased oxygen, 0.9% saline, or vasopressors. Other treatments include inferior vena cava filter placement and rapid clot burden reduction. Inferior vena cava filters prevent large clots from travelling to the heart and lungs, thus preventing serious complications. Rapid clot burden reduction involves manual aspiration using a balloon to remove the blood clot. 

  • New treatment includes Vitamin K antagonists and the Einstein Pulmonary embolism trials involving rivaroxaban. Rivaroxaban competitively binds with factor X after its activation. Rivaroxaban resulted in decreased bleeding compared to the other commonly used anticoagulants enoxaparin/warfarin. Rivaroxaban is also given in smaller, more patient-friendly doses. 

References

  • Tapson, Victor. "Pulmonary Embolism (PE)." Merck Manual. http://www.merckmanuals.com/professional/pulmonary-disorders/pulmonary-embolism-pe/pulmonary-embolism-pe
  • Pena, Constantino. "Inferior Vena Cava Filter Placement and Removal." http://www.radiologyinfo.org/en/info.cfm?pg=venacavafilter
  • Eesa, M., et. al. "Manual aspiration thrombectomy through balloon-tipped guide catheter for rapid clot burden reduction in endovascular therapy for ICA L/T occlusion." Neuroradiology. 2012 Nov;54(11):1261-5.
  • Doheny, Kathleen. "Comparing the New Blood Thinners to Warfarin." http://www.rxlist.com/script/main/art.asp?articlekey=170265
  • http://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/basics/definition/con-20022849