Pulmonary Embolism and VTE Overview

Pulmonary Embolism (PE)

• PE is a pulmonary arterial bed occlusion, most commonly due to a thrombus.
• It is the 3rd most common cause of cardiovascular death, after ACS and stroke.
• It's one of the most preventable causes of death in hospitalized patients.

Virchow's Triad

• Virchow's Triad describes the causes of blood clots:
  • Venous return decreases
  • Blood stagnates
  • Thrombus forms

Venous Thrombembolism (VTE)

• VTE is a common condition. Deep venous thrombosis (DVT) and pulmonary thromboembolism (PE) are its two main components.

Epidemiology

• The general population incidence is approximately 60-120 cases per 100,000 people per year.
• Older individuals (70-79 years old) have a higher incidence: 300-500 cases per 100,000.
• Incidence is higher in hospitalized patients

Predisposing factors

• Factors related to PE/DVT are categorized based on:
  • Degree of risk increase (major, moderate, minor)
  • History (genetically inherited or acquired)
  • Duration (transient or persistent)

Major predisposing factors for DVT

• Major surgical intervention
• Hip or knee replacement
• Lower limb fractures
• Spinal cord injuries
• Major trauma

Moderate predisposing factors for DVT

• Pregnancy/hormonal treatments/birth control pills
• Chronic heart failure
• Thrombophilia
• Central venous catheters
• Chemotherapy
• Malignancy

Minor predisposing factors for DVT

• Age

• Obesity

• Varicose veins

• Laparoscopic surgery

• Prolonged immobilization

• Up to 30% of PE cases are idiopathic (unknown cause).

Hemodynamic consequences

• Thrombus obstruction leads to:
  • Acute pulmonary hypertension
  • Increased right ventricular (RV) afterload
  • RV failure
  • Hemodynamic collapse
  • Death

Thrombus size

• Small thrombi travel and block smaller arteries (distal PE).
• Larger thrombi block lobar or main pulmonary arteries (proximal PE).
• Proximal PE has a more dramatic clinical picture.
• Distal PE has a milder course

Symptoms

• Common symptoms include dyspnea (80%), pleuritic chest pain (52%), retrosternal chest pain (12%), cough (20%), syncope (19%), and hemoptysis (11%).

Signs

• Common signs include tachypnea (70%), tachycardia (26%), DVT associated signs (15%), cyanosis (11%), and fever (7%).

Diagnosis

• Diagnosis relies on a combination of:
  • Clinical presentation
  • Risk factors
  • Imaging (e.g., CTPA, V/Q scan, ultrasound)
  • Wells probability score

Wells Score for DVT Assessment

• Used to assess the probability of PE/DVT.

ECG

• Tachycardia is the most frequent change.
• RV strain pattern is seen in inferior leads (V1-V4).
• S1Q3T3 pattern has high specificity but low sensitivity, can highlight other pathologies

Chest X-ray

• Used to exclude other causes, but has low sensitivity and specificity.
• Can show abnormalities like atelectasis, pleural effusion, or cardiomegaly.
• Specific signs such as Westermark or Hampton hump, but also low sensitivity

ABG (arterial blood gas)

• Used to assess O2 and CO2 levels, pH of the blood.
• Moderate sensitivity and very low specificity
• Can evaluate the need for ventilation

Cardiac Biomarkers

• BNP, NT-proBNP, troponins can increase due to RV strain.
• Low specificity.

D-Dimers

• Fibrin degradation products.
• High sensitivity, low specificity.
• Used to rule out low-probability cases

Ultrasound of lower limbs

• Fast, non-invasive.
• Evaluates for DVT.
• Highlights non-compressibility of veins.
• Visualizes the thrombus; higher sensitivity for proximal DVT.

CTPA (Computed Tomography Pulmonary Angiography)

• High sensitivity and specificity.
• Quick, relatively available.
• Highlights alternative diagnosis when PE is ruled out.

V/Q scan

• Alternative to CTPA.
• Lower availability, higher cost.
• Lower radiation doses.
• Can be false-positive due to other lung pathologies.

Echocardiography

• Fast, non-invasive.
• Used in emergency scenarios if other imaging techniques are unavailable/too slow.
• Detects acute pulmonary hypertension and RV strain/failure.
• Can show McConnell sign.

PESI- Pulmonary embolism severity score

• A scoring tool to assess PE severity to guide management, useful for determining appropriate intensity of care.

Treatment

• Treatment approaches for PE/DVT include
  • Reperfusion (e.g., thrombolysis, mechanical thrombectomy).
  • Anticoagulation (used to prevent future clots).
  • Prophylaxis (e.g., to prevent thrombus formation).

Acute Phase

• Supportive therapy based on the case; oxygen therapy.
• Saline, inotropes (dobutamine), and vasopressors, as needed

Thrombolysis

• Use of thrombolytic agents (tPA) to dissolve the thrombus..
• Can be used during the first two weeks following suspected thrombus formation, but not suitable for low-risk patients.

Mechanical Thrombectomy

• Surgical intervention to remove the thrombus, when IV thrombolysis is contraindicated.

Anticoagulation

• Prevents the formation of new clots.

• Heparins (unfractionated, low-molecular-weight heparins), Vitamin K antagonists, and Direct Oral Anticoagulants (DOACs) are used.

Chronic Phase

• Prolonged anticoagulation is required for patients with provoked PE for 3 months.
• Prolonged anticoagulation is required for patients with unprovoked PE for at least 6 months, depending on the risk factors.
• Lifetime anticoagulation is needed for patients with recurrent or idiopathic PE.

Prophylaxis

• Early post-operative mobilization.
• Graduated compression stockings.
• Intermittent pneumatic compression.
• inferior vena cava (IVC) filters
• Anticoagulation

Take Home Messages

• PE can rapidly progress and present dramatically.
• Timely diagnosis and appropriate treatment (anti-coagulation and thrombolytics) are crucial.
• Probability scores and severity scores guide the management of PE.
• Preventative measures in high-risk patients are essential.

This quiz covers essential aspects of pulmonary embolism (PE) and venous thromboembolism (VTE). Participants will learn about the causes, epidemiology, and predisposing factors of these conditions. Test your knowledge on Virchow's Triad and the significance of PE in hospitalized patients.