Cardiovascular · Year 1 · from Cardiovascular

Case 2: Pulmonary Embolism with Hemodynamic Compromise

Patient Presentation

Demographics: 45-year-old male

Chief Complaint: Sudden onset of severe shortness of breath and near-syncope

History of Present Illness: A 45-year-old male with recent arthroscopic knee surgery 10 days ago presents with sudden onset of severe dyspnea and near-syncope that occurred while walking to the bathroom. He describes sharp, pleuritic chest pain on the right side. He has been relatively immobile since surgery due to pain. He reports no prior episodes of blood clots. He noticed mild right calf swelling yesterday but attributed it to the surgery.

Physical Examination:

  • Vital Signs: BP 88/60 mmHg, HR 118 bpm, RR 28/min, SpO2 88% on room air
  • General: Anxious, diaphoretic, in moderate respiratory distress
  • Cardiovascular: Tachycardic, loud P2, right ventricular heave, elevated JVP
  • Lungs: Clear to auscultation bilaterally
  • Right Lower Extremity: Mild calf swelling, tenderness

Workup

  • ECG:
  • Sinus tachycardia, 118 bpm
  • S1Q3T3 pattern (deep S in lead I, Q wave and inverted T in lead III)
  • Right axis deviation
  • T wave inversions V1-V4 (RV strain)
  • Labs:
  • D-dimer: 8.4 mcg/mL (markedly elevated)
  • Troponin I: 0.48 ng/mL (elevated - RV strain)
  • BNP: 680 pg/mL (elevated)
  • ABG: pH 7.48, pCO2 28, pO2 58, HCO3 22 (respiratory alkalosis, hypoxemia)
  • CT Pulmonary Angiography:
  • Large saddle embolus at main pulmonary artery bifurcation
  • Bilateral lobar and segmental emboli
  • RV:LV ratio 1.4 (RV dilation)
  • Echocardiogram:
  • Dilated RV with hypokinesis
  • McConnell sign (RV free wall akinesis with apical sparing)
  • D-shaped LV (septal flattening)
  • Moderate tricuspid regurgitation, PASP 55 mmHg

Diagnosis

Submassive (intermediate-high risk) pulmonary embolism with right ventricular dysfunction

Hemostasis and Thrombosis Correlation:

Pathophysiology of PE:

  1. Thrombus Origin:
  • Originated from right calf DVT
  • Dislodged and embolized through venous system
  • Traveled through right heart to pulmonary circulation
  • Lodged at bifurcation (saddle embolus)
  1. Mechanical Obstruction:
  • Large clot burden obstructs pulmonary arteries
  • Acute increase in pulmonary vascular resistance
  • Right ventricle faces sudden pressure overload
  • RV cannot acutely handle increased afterload
  1. Vasoactive Mediator Release:
  • Platelet-derived serotonin causes vasoconstriction
  • Thromboxane A2 further increases PVR
  • Additional pulmonary vasoconstriction beyond mechanical obstruction
  1. Right Heart Failure Cascade:
  • RV dilation to maintain output (Frank-Starling)
  • Septal shift compromises LV filling
  • Reduced cardiac output and hypotension
  • RV ischemia from increased wall stress and reduced coronary perfusion

Why hypoxemia occurs:

  • V/Q mismatch: perfused lung receiving ventilation, occluded areas not perfused
  • Increased dead space ventilation
  • Right-to-left shunt if foramen ovale opens from elevated RA pressure

Risk Stratification:

  • Hemodynamically unstable = High-risk (massive) PE
  • RV dysfunction + elevated biomarkers = Intermediate-high risk
  • This patient: Submassive with borderline BP

Coagulation System Activation:

  • Recent surgery caused tissue factor release
  • Immobility caused venous stasis
  • Classic post-operative hypercoagulable state

Treatment

  1. Immediate stabilization:
  • IV fluid bolus (cautious - avoid RV overload)
  • Supplemental oxygen (high-flow)
  • Vasopressors if persistent hypotension (norepinephrine)
  1. Anticoagulation:
  • Unfractionated heparin IV (preferred for potential intervention)
  • 80 units/kg bolus, then 18 units/kg/hr infusion
  • Target aPTT 60-80 seconds
  1. Consider systemic thrombolysis:
  • Given borderline hemodynamics and RV dysfunction
  • Alteplase 100 mg over 2 hours if deterioration
  1. Alternative: Catheter-directed therapy
  • Catheter-directed thrombolysis
  • Mechanical thrombectomy
  1. Transition to oral anticoagulation:
  • After stabilization, minimum 3 months
  • Provoked PE (surgery) - 3 months may suffice
  1. IVC filter: Only if anticoagulation contraindicated

Clinical Pearl

Understanding the Hemostatic Balance: This case demonstrates how the protective hemostatic system (designed to prevent bleeding after injury) can become pathological when Virchow's triad elements converge. The coagulation cascade that normally stops bleeding after surgery instead formed a life-threatening venous clot that embolized to the lungs.

Key Hemostasis Concepts Illustrated:

  • Primary hemostasis (platelet plug) and secondary hemostasis (fibrin) both contribute to venous thrombi
  • Venous thrombi are "red clots" - rich in fibrin and trapped RBCs
  • D-dimer elevation reflects ongoing fibrinolysis attempting to dissolve the clot
  • Anticoagulation prevents clot propagation while endogenous fibrinolysis resolves existing thrombus

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