Pulmonology · Venous Thromboembolism
The facts most likely to be tested
Massive pulmonary embolism is defined by the presence of sustained hypotension (systolic blood pressure <90 mmHg) or the requirement for inotropic support.
Right ventricular (RV) strain on echocardiogram or CT pulmonary angiography is the hallmark of hemodynamic instability in pulmonary embolism.
Bedside echocardiography is the diagnostic test of choice for the hemodynamically unstable patient when CT pulmonary angiography is not immediately feasible.
Systemic thrombolysis with tPA (alteplase) is the first-line treatment for patients with massive pulmonary embolism who do not have absolute contraindications.
Surgical embolectomy or catheter-directed thrombolysis is indicated for patients with massive pulmonary embolism who have absolute contraindications to systemic fibrinolysis.
Obstructive shock in massive pulmonary embolism results from acute right ventricular failure leading to decreased left ventricular preload and subsequent cardiovascular collapse.
Intravenous fluid boluses should be administered with extreme caution in massive pulmonary embolism to avoid worsening right ventricular distension and septal bowing.
Vignette unlocked
A 58-year-old male is brought to the emergency department after a sudden syncopal episode. On arrival, he is diaphoretic and tachypneic. His blood pressure is 82/50 mmHg, heart rate is 124 bpm, and oxygen saturation is 88% on room air. Physical exam reveals distended jugular veins and a loud pulmonic component of the second heart sound. Bedside ultrasound demonstrates a dilated right ventricle with septal flattening during diastole.
What is the most appropriate next step in management?
Systemic thrombolysis (tPA)
The patient presents with massive pulmonary embolism characterized by sustained hypotension and obstructive shock, necessitating immediate systemic thrombolysis as the primary intervention.
Full handout
High yield triage
Etiology / Epidemiology
Defined by hemodynamic instability (systolic BP <90 mmHg). Driven by Virchow's triad: stasis, hypercoagulability, endothelial injury.
Clinical Manifestations
Presents with syncope, hypotension, and obstructive shock. Look for S1Q3T3 on ECG and tachycardia.
Diagnosis
CT pulmonary angiography (CTPA) is the gold standard. Bedside echocardiography showing right ventricular strain is critical.
Treatment
Systemic thrombolysis (tPA) is first-line. Absolute contraindications include active internal bleeding or history of hemorrhagic stroke.
Prognosis
High mortality without intervention. Right ventricular failure is the primary cause of death.
Full handout
Epidemiology & Etiology
Massive PE is a life-threatening event characterized by acute right heart failure. Primary risk factors include recent surgery, malignancy, prolonged immobilization, and oral contraceptive use. Genetic predispositions like Factor V Leiden significantly increase baseline risk.
Pertinent Anatomy
The embolus lodges in the pulmonary artery or its major branches. This creates a high-pressure obstruction leading to acute right ventricular (RV) dilation and septal bowing into the left ventricle.
Pathophysiology
Obstruction causes an immediate increase in pulmonary vascular resistance (PVR). The RV, unaccustomed to high afterload, fails rapidly, leading to decreased left ventricular preload and systemic hypotension. This cycle of obstructive shock results in profound tissue hypoxia and cardiovascular collapse.
Clinical Manifestations
Patients present with sudden onset dyspnea, syncope, and cyanosis. Physical exam reveals tachycardia, hypotension, and jugular venous distension. Red flags include altered mental status and cold, clammy extremities indicating shock.
Diagnosis
The CT pulmonary angiography (CTPA) is the definitive diagnostic test. In unstable patients unable to undergo CT, bedside echocardiography demonstrating RV hypokinesis or McConnell's sign is diagnostic for massive PE.
Treatment
Immediate systemic thrombolysis (alteplase) is indicated for hemodynamically unstable patients. Absolute contraindications include recent intracranial surgery or active bleeding. If thrombolysis fails or is contraindicated, surgical embolectomy or catheter-directed therapy is required.
Prognosis
Mortality rates exceed 30% without rapid reperfusion. Survivors require long-term anticoagulation to prevent recurrence and monitoring for chronic thromboembolic pulmonary hypertension.
Differential Diagnosis
Cardiac Tamponade: Beck's triad (hypotension, JVD, muffled heart sounds)
Myocardial Infarction: ST-segment elevation on ECG
Aortic Dissection: Tearing chest pain radiating to the back
Tension Pneumothorax: Absent breath sounds and tracheal deviation
Septic Shock: Fever and source of infection