Course 03: Cardiovascular, Vascular and Hematology
Lesson 9 of 12. Read the diagnostic framework and case, then complete the 10-question practice set. All material is original educational content; high-risk presentations require emergency referral.
VTE risk and presentation
- DVT may present with unilateral swelling, tenderness and asymmetry; PE may cause pleuritic chest pain, acute dyspnea, tachycardia, syncope or hypoxemia.
- Recognize precipitating risk: surgery, immobility, cancer, estrogen exposure, pregnancy/postpartum and prior VTE.
- A normal oxygen saturation does not rule out pulmonary embolism, and not every calf pain is DVT.
- Hemodynamic instability with suspected PE requires emergency care and rapid specialist evaluation.
Probability-led diagnosis
- Use a validated pretest probability tool (e.g., Wells criteria) in appropriate stable patients before choosing D-dimer or imaging.
- D-dimer can help rule out VTE in appropriately low-probability situations, but a positive value is nonspecific.
- Compression venous ultrasonography evaluates suspected lower-limb DVT; CT pulmonary angiography or alternative imaging evaluates PE when indicated.
- Do not delay emergency assessment to arrange outpatient D-dimer testing in a hemodynamically unstable patient.
Anticoagulant principles
- Anticoagulation prevents thrombus extension and recurrence; agent choice is affected by renal function, pregnancy, active malignancy, bleeding risk, weight and drug interactions.
- Oral factor Xa inhibitors and direct thrombin inhibitors are used in many VTE and AF settings, but selection, dosing and duration are indication-specific.
- Warfarin requires INR monitoring and interaction review; mechanical heart valves are a prominent indication for vitamin K antagonist rather than DOAC therapy.
- Distinguish anticoagulants from antiplatelets: they target different clotting mechanisms and cannot be freely substituted.
Bleeding safety
- Major bleeding warning signs include hematemesis, melena, intracranial symptoms, unexplained hypotension and severe bruising.
- Ask about NSAIDs, OTC aspirin, herbal supplements and alcohol when reviewing bleeding risk.
- Before procedures or medication changes, review renal function and consult the treating anticoagulation team; do not stop medication independently.
- Reversal decisions depend on agent and urgency and belong to hospital protocols.
Follow-up and patient education
- Explain adherence, missed-dose instructions specific to the prescribed agent, and when to seek emergency help.
- Consider provoking factors, persistent risks and patient preferences when selecting VTE treatment duration.
- Document a clear follow-up plan and monitoring for recurrent symptoms, bleeding and medication complications.
Applied clinical case
A 42-year-old on combined oral contraceptives has a new swollen painful calf after prolonged travel, but normal BP and oxygen saturation.
Show model clinical reasoning and disposition
Assess clinical probability, choose compression ultrasound and D-dimer only as appropriate to the probability pathway, and review alternative diagnoses and bleeding risk.
Clinical self-check
- When is D-dimer helpful?
- What makes suspected PE an immediate emergency?
- How do DOACs differ from warfarin?
Guidelines and further learning
- AHA/ACC — Atrial Fibrillation Clinical Practice Guideline (external)
- Canadian Cardiovascular Society — Guidelines Library (external)