Terminology

Preprocedure

Procedure

Outcomes

Definitions

• Pulmonary embolism (PE): Embolized blood clot within pulmonary artery (PA) causing obstruction and altered lung perfusion
  • Estimated annual incidence: 1/1,000
  • 3rd most common cause of cardiovascular death in USA per year
  • Deep vein thrombosis (DVT) is most common cause
  • Variable symptoms
    • Asymptomatic
    • Chest pain, dyspnea, cough, palpitations
    • Hypotension, syncope, cardiogenic shock, death
• Right ventricular (RV) dysfunction: Dilation, impaired function and ischemia that occurs in setting of acute PE as result of increased afterload
  • Present in 45% of patients with PE
  • Associated with increased mortality (25% if normotensive, up to 65% if hypotensive)
  • If untreated, ultimately progresses to cause decreased left ventricular (LV) output, cardiogenic shock, and death
  • Imaging
    • CTA: Increased RV:LV ratio (> 0.9), reflux of contrast into hepatic veins
    • Echo: RV dilatation, impaired contractility
  • Laboratory: Evidence of myocardial necrosis [elevated troponin or brain natriuretic peptide (BNP)]
• Chronic thromboembolic pulmonary hypertension (CTEPH): Subtype of pulmonary hypertension (PH) that develops from nonresolution of PE
  • Develops in ~ 4% of patients with PE
  • Presence of obstructive fibrotic thromboembolic material in major pulmonary vessels
  • Causes progressive, severe right heart failure
• Catheter-directed thrombolysis (CDT): Infusion of thrombolytics through catheter positioned directly in PA
• Mechanical thrombectomy (MT): Mechanical disruption and removal of thrombus via suction without thrombolytics

Risk Stratification

• European Society of Cardiology (ESC) risk stratification (2019)
  • Low risk: No shock, signs of RV dysfunction, or elevated cardiac biomarkers (troponin/BNP)
  • Intermediate risk: RV dysfunction, no shock or hypotension
    • Intermediate-low risk: Without elevated cardiac biomarkers (troponin/BNP)
    • Intermediate-high risk: With elevated cardiac biomarkers (troponin/BNP)
  • High risk: RV dysfunction with shock or hypotension
• PE Severity Index (PESI) Score
  • Escalating levels of severity (class I to class V), corresponding to escalating 30-day mortality risk (1-25%)
  • Calculated with demographic and clinical information rather than imaging/labs
    • Demographic: Age, sex
    • Comorbidities: Cancer, heart failure, chronic lung disease
    • Clinical findings: Pulse, blood pressure, respiratory rate, temperature, mental status, O₂ saturations
  • Simplified PESI score (sPESI)
    • Simplified scoring splitting into 2 groups
      • 0 points: Low risk (< 1% 30-day mortality), can potentially be treated outpatient
      • > 1 point: Elevated risk, can be further stratified with full PESI
    • Points awarded for: Age > 80 years, history of cancer/CHF/COPD, pulse > 110, systolic blood pressure (SBP) < 100, or O₂ saturations < 90%
  • Massive/submassive: Terminology falling out of favor, not descriptive enough to risk stratify or estimate mortality

Systemic Therapy

• Anticoagulation
  • Options include warfarin (vitamin K antagonist), novel oral anticoagulants (NOACs), such as rivaroxaban, apixaban, dabigatran, or low-molecular-weight heparin
    • Warfarin therapy most cost effective but requires regular interval monitoring of patient's international normalized ratio (INR)
    • NOACs do not require therapeutic monitoring but tend to be more expensive
  • Patient's renal function, comorbidities, and preference should be taken into account when selecting anticoagulation regimen
• Systemic thrombolysis
  • Peripheral administration of tissue plasminogen activator (tPA)
    • Variable dosing strategies, but 50 mg commonly used
  • Significantly reduces mortality compared to anticoagulation alone in high-risk PE
  • Increased risk of major bleeding, including intracranial hemorrhage
    • May be contraindicated in certain patients

Catheter-Directed Therapies

• Generally reserved for patients with intermediate-high or high-risk PE
• CDT
  • Placement of catheters into pulmonary arteries for direct tPA infusion, usually 1 mg of tPA/hour over 24-48 hours
  • Can be done ± US assistance
    • No clear consensus of benefit
  • ULTIMA trial (2014): CDT superior to anticoagulation in improving RV dilation
  • SEATTLE II study (2015): Decreased RV dilation, PH, and thrombus burden with fewer instances of intracranial hemorrhage
• MT
  • Multiple commercially available devices for direct aspiration &/or mechanical disruption of clot
  • Do not require use of thrombolytics, and thus have decreased risk of major bleeding
  • Indigo System (Penumbra Inc)
    • Aspiration catheter (multiple options up to 12 Fr) with continuous vacuum
    • Also used for peripheral arterial and venous systems
    • EXTRACT-PE trial (2021): Significant reduction in RV:LV ratio, low major adverse events
  • FlowTriever (Inari Medical)
    • Large-bore aspiration system (16-24 Fr) with negative suction-locking syringe
      • Optional coaxial component for clot disruption
    • Wible et al (2019): Significant reduction of mean PA pressure with good safety and survival profile
    • Buckley et al (2021): Improved mortality and decreased ICU length of stay for those with central PE of elevated risk (PESI 4/5 and ESC intermediate-high/high risk)

Treatment of Low-Risk Pulmonary Embolism

• CHEST guidelines: Isolated subsegmental PE may not require treatment in low-risk patients
• Low clinical risk patients (sPESI 0) diagnosed in ER may not require hospital admission in order to initiate anticoagulation

Indications

Contraindications

Preprocedure Imaging

Getting Started

Patient Position/Location

Procedure Steps

Findings and Reporting

Alternative Procedures/Therapies

Things to Do

Things to Avoid

Problems

Complications

Expected Outcomes