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Blood and Clots Quizlet 1: Oral Contraceptives and Pulmonary Embolism

In Blood & Clots, Medical Concepts by Eric Tseng3 Comments

Hello Blood & Clots/CanadiEM community!

Before we post our blog series on thrombosis and bleeding, we encourage you to test your initial knowledge by going through a few brief case scenarios. These cases were originally posted as part of our needs assessment in Fall 2016, and you can find the answers after each question below.

The Introduction to Blood and Clots post can be found here.

All the content from the Blood and Clots series can be found here.

Yours sincerely,

The Blood & Clots Team

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QUIZLET #1

Case Vignette

Maria is a 27-year-old female university student with no past medical or surgical history, and has been taking an oral contraceptive pill for the past 8 years. She has never smoked. 2 days ago, she developed a new sharp pain on her right upper back. Initially she thought this to be a muscle strain from power yoga, but it has been getting progressively worse and is painful when she breathes in. She denies fever or chills, but says that she seems to be having a dry cough when exerting for her daily cycling class and has felt tired during classes. She denies shortness of breath or syncope. She tells you, “I know it’s probably just the flu now, but I want to be sure, because my grandmother had a blood clot”.

On examination, Maria is a well-appearing, average sized young woman. Her vitals reveal T=37C, HR 85, BP 110/90, RR 15, SpO2 99% RA. Head and neck exam is normal. Cardiorespiratory examination is normal and there is no jugular venous distension. The chest pain is not reproducible with palpation or movement. She does endorse mild bilateral calf pain that she attributes to running. ECG performed at triage shows NSR and no signs of S1Q3T3 or RBBB.

Question 1: What is the pre-test probability for pulmonary embolism?

A) Unlikely: Given her age, she probably has a viral infection and/or musculoskeletal chest pain

B) Unlikely: Her Wells Score is <4.5; does not have signs or symptoms of DVT or PE, and has no past medical or surgical history

C) Likely: She has a new exertional cough without signs and symptoms of infection, and has been on long term oral contraceptive.

D) Likely: There is no alternative diagnosis more likely than PE

E) Insufficient information

Answer to Question 1

B) Unlikely: Her Wells Score is <4.5; does not have signs or symptoms of DVT or PE, and has no past medical or surgical history

Statistically and based on the clinical presentation, A is a reasonable answer as she has an unlikely clinical pretest probability by the Wells Score. Of note, because Maria uses combined oral contraceptive pills, she does not fit under criteria to place her in a low risk group based on PERC criteria (PMID: 18318689). C is incorrect because her clinical presentation and signs and symptoms are not high risk enough to place her in a group to treat empirically based on her Wells’ Score. D is incorrect because she has alternative diagnoses.

Question 2: What is the most appropriate next step?

A) Discharge her home with instructions to monitor for worsening of pain or shortness of breath. This is unlikely to be PE.

B) Order a D-Dimer test. She has a low likelihood of PE, and D-Dimer can be used to rule out PE.

C) Empiric anticoagulation with LMWH or a DOAC, and then CTPA in the morning. She has a moderate likelihood of VTE because of her symptoms and hormonal therapy.

D) Empiric anticoagulation with LMWH or a DOAC, and then a V/Q scan in the morning. She has a moderate likelihood of VTE because of her symptoms and hormonal therapy.

E) Empiric anticoagulation with LMWH or a DOAC; admit her overnight for and arrange for a V/Q scan in the morning. She has moderate likelihood of PE because of her symptoms and hormonal therapy

Answer to Question 2

B) Order a D-Dimer test. She has a low likelihood of PE, and D-Dimer can be used to rule out PE.

Maria has unlikely pretest probability by the Wells Score due to her clinical presentation. Combined oral contraception (COC) does increase her baseline risk of VTE, and this risk is highest in the first 6-12 months after COC has been started. While this risk does diminish with prolonged use (past 12-24 months) it continues to be elevated relative to baseline (PMID: 19679614). The fact that Maria has been on the COC for 8 years suggests she is likely at lower risk compared to someone who started COC only 3 months prior.

In this situation her pre-test probability is driven not by her COC but her clinical presentation. Therefore, it is reasonable to perform a D-Dimer test to exclude pulmonary embolism as she is low pretest probability. This conservative approach may obviate the need for CT scan and avoid radiation exposure.

Question 3: You discover that she has a family history of a hypercoagulable disorder. How does this change management?

A) This is highly unlikely to be a PE. Discharge home with instructions to monitor for change or worsening of pain and/or shortness of breath. Thrombosis service may be consulted.

B) This has a low likelihood of being a PE. D-dimer may be employed to rule out VTE.

C) She may be given a dose of LMWH or a DOAC with instructions to return for CTPA in the morning.

D) She may be given a dose of LMWH or a DOAC with instructions to return for V/Q scan in the morning.

E) She may be given a dose of LMWH or a DOAC and admitted for overnight observation and V/Q scan in the morning.

Answer to Question 3

B) This has a low likelihood of being a PE. D-dimer may be employed to rule out VTE.

The rationale for 1B also applies here. Although Maria endorses a family history of thrombosis, she has no personal history of venous thromboembolism (VTE) and this family history does not change her clinical pretest probability. D-Dimer continues to be an appropriate diagnostic test in this situation to rule out pulmonary embolism and she does not require empiric anticoagulation or a CT scan.

If there is a confirmed family history of VTE and hereditary thrombophilia, an outpatient consultation with a thrombosis specialist could be considered. The purpose of such a consult would be to provide counseling about her risk of VTE with ongoing use of the combined oral contraceptive pill, which increases her baseline risk of VTE (PMID: 27121914).

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Eric Tseng

Eric Tseng

Dr. Eric Tseng is a hematologist who works at St. Michael’s Hospital and the University of Toronto. His clinical practice is focused on non-cancer hematology and thrombosis medicine. His academic interests are in postgraduate medical education and competency based education.
Calvin Yeh

Calvin Yeh

Calvin is a MD/PhD student at McMaster University. Calvin completed PhD studies under Dr. Jeffrey Weitz at the Thrombosis and Atherosclerosis Research Institute. He focussed on the biochemical mechanism and regulation of the coagulation system in the context of anticoagulant drugs including the new (direct) oral anticoagulants.
Andrew Shih

Andrew Shih

Dr. Andrew Shih works as a Transfusion Medicine specialist at Vancouver Coastal Health Authority. His interests include education regarding the safety and appropriate utilization of blood products and advance blood transfusion as a personalized medical therapeutic intervention.
Kerstin de Wit

Kerstin de Wit

Kerstin de Wit works clinically in Thrombosis medicine and Emergency Medicine in Hamilton, Ontario. Her research focuses on bleeding, clotting, and anticoagulation in the emergency department.
Teresa Chan

Teresa Chan

Senior Editor at CanadiEM
Emergency Physician. Medical Educator. #FOAMed Supporter, Producer and Researcher. Assistant Professor, Division of Emergency Medicine, Department of Medicine, McMaster University. + Teresa Chan
Teresa Chan
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